Question about 2006 Chevrolet Silverado 3500

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2006 CHEV TRUCK PRNDL DISPLAY BLANK

HAS A CODE U1000 LOSS OF CLASS 2 DATA TO IPC. CHECKED ALL POWER, GROUNDS, SERIAL DATA, AND CLASS 2 COMMUNICATION AT IPC ELECTRICAL CONNECTOR, ALL IS OK. SUSPECT THE TROUBLE TO BE INTERNAL TO THE CLUSTER?

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Its in your cluster, most likely the gauge its self

Posted on Jan 28, 2009

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My mph, gas, and temp gauges are not working


That's why you don't let you husband work on your car ! Unless he does it for a living .. For MPH there is a VSS - vehicle speed sensor , for the gas there is a sending unit in the fuel tank, for the temp. gauge there is a temp. sensor located in coolant stream on the engine .You more then likely need to have you instrument cluster repaired . GM had a problem with step motors inside the instrument cluster . A step motor is what controls the individual gauge. The sensors are all inputs to the PCM - powertrain control module (engine computer ) .
Engine Coolant Temperature Gage
The IPC displays the engine coolant temperature as determined by the PCM. The IPC receives a class 2 message from the PCM indicating the engine coolant temperature. The engine coolant temperature gage defaults to C or below if:
?€¢
The PCM detects a malfunction in the engine coolant temperature sensor circuit.


?€¢
The IPC detects a loss of class 2 communications with the PCM.

Fuel Gage
The IPC displays the fuel level as determined by the PCM. The IPC receives a class 2 message from the PCM indicating the fuel level percent. The fuel gage defaults to empty if:
?€¢
The PCM detects a malfunction in the fuel level sensor circuit.


?€¢
The IPC detects a loss of class 2 communications with the PCM.

When the fuel level is less than 14% (84ohms), the low fuel indicator illuminates.
Odometer
The IPC contains a season odometer and a trip odometer. Momentarily press the trip select/reset switch in order to toggle between the season odometer and the trip odometer. Press the trip select/reset switch for greater than 1.5 seconds, while the trip odometer is displayed, in order to reset the trip odometer. The IPC displays the vehicle mileage and trip mileage as determined by the IPC. The IPC calculates the mileage based on the vehicle speed information from the PCM. The odometer will display 'error' if an internal IPC memory failure is detected.
PRNDL Display
The IPC displays the selected gear position as determined by the PCM. The IPC receives a class 2 message from the PCM indicating the gear position. The PRNDL display shall flash all gear positions if:
?€¢
The PCM detects a malfunction in the transmission range switch circuit.


?€¢
The IPC detects a loss of class 2 communications with the PCM.

Speedometer
The IPC displays the vehicle speed based on the information from the PCM. The PCM converts the data from the vehicle speed sensor to a 4000 pulses per mile signal. The IPC uses the vehicle speed signal circuit from the PCM in order to calculate the vehicle speed. The speedometer defaults to 0 mph (0 kph) if a malfunction in the vehicle speed sensor circuit exists.
Tachometer
The IPC displays the engine speed as determined by the PCM. The IPC receives a class 2 message from the PCM indicating the engine speed. The tachometer will default to 0 rpm if:
?€¢
The PCM detects a malfunction in the engine speed sensor circuit.


?€¢
The IPC detects a loss of class 2 communications with the PCM.

May 22, 2016 | 2002 Buick Century

1 Answer

I have a 2010 Chevy impala LS instrument cluster and it has a 20 pin plug I'm trying to figure out which wire's on the back of the cluster are for the speed sensor, rpm, gas, and temp wires.


Boy your way off base . All the gauges are inputs from the ECM - engine computer . The VSS - vehicle speed sensor , ETC - engine coolant temp sensor , sending unit in the fuel tank , All this sensors input the engine computer . The PCM then sends this info on the GMLAN serial data bus ,communications network . The Instrument cluster has a microprocessor inside that translates this info an controls the gauges. You probably have an instrument cluster problem or a communication network problem . Your best bet is to take your vehicle to the dealer or some other qualified repair shop. Need to have it checked for DTC'S - diagnostic trouble codes.
Indicators and Warning Messages
Refer to Indicator/Warning Message Description and Operation.
Engine Coolant Temperature Gage
The instrument panel cluster (IPC) displays the engine coolant temperature as determined by the engine control module (ECM). The IPC receives a serial data message from the ECM indicating the engine coolant temperature. The IPC receives the coolant temperature information via serial data message from the body control module (BCM). The engine coolant temperature gage defaults to 60?°C (140?°F) or below if:
?€¢
The ECM detects a malfunction in the engine coolant temperature sensor circuit.

?€¢
The IPC detects a loss of serial data communications with the ECM.

?€¢
The IPC detects a loss of serial data communications with the BCM.
Fuel Gage
The instrument panel cluster (IPC) displays the fuel level as determined by the engine control module (ECM). The IPC receives a serial data message from the ECM indicating the fuel level percent. The body control module (BCM) sends the fuel level information from the ECM to the IPC via a serial data message indicating the fuel level percent. The fuel gage defaults to empty if:
?€¢
The ECM detects a malfunction in the fuel level sensor circuit.

?€¢
The IPC detects a loss of serial data communications with the ECM.

?€¢
The IPC detects a loss of serial data communications with the BCM.
When the fuel level is less than a pre-determined value, the low fuel indicator illuminates in the IPC.
Odometer
The vehicle odometer is calculated and stored electronically in the instrument panel cluster (IPC). The IPC contains a season odometer and trip odometer A or B. Momentarily press the trip/fuel button in order to toggle between the season odometer and the trip odometer. Press the set/reset button for greater than 0.25 seconds, while the trip odometer is displayed, in order to reset the trip odometer. The IPC displays the vehicle mileage and trip mileage as determined by the engine control module (ECM). The IPC calculates the mileage based on the serial data vehicle speed information from the ECM. The odometer will display 'error' if an internal IPC memory failure is detected. The odometer displays either miles or kilometers and can be set through the customization menu in the driver information center (DIC).
PRNDL Display
The instrument panel cluster (IPC) displays the selected gear position as determined by the engine control module (ECM). The IPC receives a serial data message from the ECM indicating the gear position. The PRNDL display blanks if:
?€¢
The ECM detects a malfunction in the transmission range switch circuit.

?€¢
The IPC detects a loss of serial data communications with the ECM.

?€¢
The IPC detects a loss of serial data communications with the body control module (BCM).
Speedometer
The instrument panel cluster (IPC) displays the vehicle speed as determined by the engine control module (ECM). The IPC calculates the mileage based on serial data vehicle speed information from the ECM. The IPC receives vehicle speed information from the body control module (BCM) via a serial data message. The speedometer defaults to 0 km/h (0 mph) if the IPC detects a loss of serial data communications with the ECM or BCM.
Tachometer
The instrument panel cluster (IPC) displays the engine speed as determined by the engine control module (ECM). The IPC receives a serial data message from the ECM indicating the engine speed. The IPC receives the engine speed information from the body control module (BCM) via a serial data message. The tachometer will default to 0 RPM if:
?€¢
The ECM detects a malfunction in the engine speed sensor circuit.

?€¢
The IPC detects a loss of serial data communications with the ECM.

?€¢
The IPC detects a loss of serial data communications with the BCM.

How to Diagnose Controller Area Network CAN Suggest you read up on C.A.N.

May 14, 2016 | Cars & Trucks

1 Answer

While driving antitheft light comes on and all the gauges go flat,car keeps runnig,want to disable system,not sure what to look for


Before doing something drastic ,have it checked out for DTC'S - diagnostic trouble codes . It may not be the anti-theft system ,gauges going flat would be more like a communication problem between modules . PCM / BCM / instrument cluster etc.. That also could cause theft light coming on . If your not sure what to look for ,take it to a ASE certified professional . You may render your vehicle useless if you don't know what your doing .
Serial Data Power Mode Master
On vehicles that have several control modules connected by serial data circuits, one module is the power mode master (PMM). On this vehicle, the PMM is the body control module (BCM). The PMM receives 3 discrete ignition switch signals to differentiate which power mode will be sent over the Serial Data circuits. The 3-wire Ignition Switch table below illustrates the state of these inputs in correspondence to the ignition switch position:
Serial Data Messages The modules that depend exclusively on serial data messages for power modes. stay in the state dictated by the last valid PMM message until they can check for the engine run flag status on the serial data circuits. If the PMM fails, the modules monitor the serial data circuit for the engine run flag serial data. If the engine run flag serial data is True, indicating that the engine is running, the modules fail-safe to RUN. In this state, the modules and their subsystems can support all operator requirements. If the engine run flag serial data is False, indicating that the engine is not running, the modules fail-safe to OFF-AWAKE. In this state, the modules are constantly checking for a change status message on the serial data circuits and can respond to both local inputs and serial data inputs from other modules on the vehicle.
Indicators and Warning Messages
Refer to Indicator/Warning Message Description and Operation .
Engine Coolant Temperature Gage
The instrument panel cluster (IPC) displays the engine coolant temperature as determined by the powertrain control module (PCM) or the engine control module (ECM). The IPC receives a serial data message from the PCM/ECM indicating the engine coolant temperature. The engine coolant temperature gage defaults to 38?°C (100?°F) if:
?€¢
The PCM/ECM detects a malfunction in the engine coolant temperature sensor circuit.


?€¢
The IPC detects a loss of serial data communications from the BCM.

Fuel Gage
The instrument panel cluster (IPC) displays the fuel level as determined by the powertrain control module (PCM) or the engine control module (ECM). The IPC receives a serial data message from the body control module (BCM) indicating the fuel level. The fuel gage defaults to E (empty) if:
?€¢
The PCM/ECM detects a malfunction in the fuel level sensor circuit.


?€¢
The IPC detects a loss of serial data communications from the BCM.

When the fuel level is less than 14 percent, the low fuel indicator illuminates.
Odometer
The instrument panel cluster (IPC) contains a season odometer and a trip odometer. Momentarily press the trip/reset switch in order to toggle between the season odometer and the trip odometer. Press the trip/reset switch for greater than 2 seconds, while the trip odometer is displayed, in order to reset the trip odometer. The odometer is calculated and stored electronically in the body control module (BCM). The BCM uses the vehicle speed information from the powertrain control module (PCM) to calculate the odometer. The odometer displays 'error' if an internal IPC memory failure is detected. The IPC stores a backup copy of the odometer value incase the IPC stops receiving a valid odometer value from the BCM.
Speedometer
The instrument panel cluster (IPC) displays the vehicle speed based on the information from the ECM/PCM. The IPC receives the vehicle speed information from the BCM via the serial data circuit. The speedometer defaults to 0 kmh (0 mph) when the following occurs:
?€¢
The powertrain control module (PCM) or the engine control module (ECM) detects a malfunction in the vehicle speed sensor circuit.


?€¢
The IPC detects a loss of serial data communication from the BCM.

Tachometer
The instrument panel cluster (IPC) displays the engine speed as determined by the powertrain control module (PCM) or the engine control module (ECM). The IPC receives a serial data message from the body control module (BCM) indicating the engine speed. The tachometer will default to 0 RPM if:
?€¢
The PCM/ECM detects a malfunction in the engine speed sensor circuit.


?€¢
The IPC detects a loss of serial data communication from the BCM.

Apr 07, 2016 | 2006 Pontiac G6

1 Answer

What are the probable causes of DTC U1000?


DTC U1000 and U1255
Class 2 Communication Malfunction , Do you know what class 2 serial data communication network is ? What module set this code an what kind of scan tool did you use to read this code .
Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. When a module receives a message for a critical operating parameter, the module records the ID number of the module which sent the message for State of Health monitoring, Node Alive messages. A critical operating parameter is one which, when not received, requires that the module use a default value for that parameter. When a module does not associate an ID number with at least one critical parameter within about 5.5 seconds of beginning serial data communication, DTC U1000 or U1255 is set. When more than one critical parameter does not have an ID number associated with it, the DTC will only be reported once.
The table below list the modules on the Class 2 Serial Data Circuit that will set a U1000 or U1255 and should be actively communicating the previously described messages on the Class 2 Serial Data Circuit.

Control Module

ID Number
Body Control Module (BCM)
064
Electronic Brake Control Module (EBCM)
040
Instrument Panel Cluster (IPC)
096
Radio
128
Powertrain Control Module (PCM)
016
Sensing and Diagnostic Module (SDM)
088
Diagnostic Aids
When a malfunction such as a open fuse to a module occurs while modules are communicating, a Loss of Communication DTC is set as current. When the modules stop communicating, ignition is turned off, the current Loss Communication DTC is cleared but the history DTC remains. When the modules begin to communicate again, the ignition is turned on, the module with the open fuse will not be learned by the other modules so U1000 or U1255 is set current by the other modules. If the malfunction occurs when the modules are not communicating, only U1000 or U1255 is set.
Test Description
The numbers below refer to the step numbers on the diagnostic table.

  1. A DTC U1001 - U1254 Lost Communications with with a history status may indicate the cause of U1000 or U1255.

  2. The modules not communicating are the likely cause of U1000 or U1255. The modules that are available on the class 2 serial data circuit are listed in the Circuit Description.

  3. The module which was not communicating due to a poor connection to the class 2 serial data circuit may have set DTC U1001 - U1254 Lost Communications with for those modules that it was monitoring.

  4. The modules which can communicate indicate the module which cannot communicate. You must clear the serial data communication DTCs from these modules to avoid future misdiagnosis.

  5. If all modules are communicating, the module which set U1000 or U1255 may have done so due to some other condition.

  6. The module which set U1000 or U1255 is the likely cause of the malfunction.

1
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Record the DTCs set in each module. If using a Tech 2, use the Class 2 DTC Check feature to determine which modules have DTCs set.
Did you record any DTCs in the range of U1001-U1254 with a history status?
Go to Diagnostic Trouble Code (DTC) List
Go to Step 2

2
  1. Turn ON the ignition, with the engine OFF.
  2. Attempt to communicate with each module on the class 2 serial data circuit. If using a Tech 2, obtain this information using the class 2 Message Monitor feature.
  3. Record all of the modules communicating on the class 2 serial data circuit.
  4. Compare the list of modules which are communicating to the list given in Circuit Description.
Does any module on the class 2 serial data circuit not communicate?
YES - Go to Step 3
NO - Go to Step 12
Test the following circuits of the module that is not communicating for an open or short to ground:
?€¢
The battery positive voltage supply circuits


?€¢
The switched battery positive supply circuits


?€¢
The battery positive voltage output circuits


?€¢
The ignition voltage input circuits


?€¢
The ignition voltage output circuits

Refer to the following:
?€¢
Control Module References in Body Control System for the applicable schematic


?€¢
Circuit Testing in Wiring Systems


?€¢
Wiring Repairs in Wiring Systems

Did you find and correct the condition?

5

Important: Inspect all connectors in the serial data communications circuit.
Refer to the following:
?€¢
Data Link Connector Schematics


?€¢
Testing for Intermittent Conditions and Poor Connections in Wiring Systems


?€¢
Connector Repairs in Wiring Systems

  1. Turn OFF the ignition.
  2. Test the class 2 serial data circuits of the module that is not communicating for an open. Refer to the following:
?€¢
Data Link Connector Schematics


?€¢
Circuit Testing in Wiring Systems


?€¢
Wiring Repairs in Wiring Systems

Did you find and correct the condition?
Go to Step 8
Go to Step 6

6
Inspect the harness connector of the module that is not communicating for poor connections and terminal tension at the following circuits:
?€¢
The battery positive voltage input circuits


?€¢
The switched battery positive voltage supply


?€¢
The battery positive voltage output circuits


?€¢
The ignition voltage input circuits


?€¢
The ignition voltage output circuits


?€¢
The ground circuits


?€¢
The class 2 serial data circuits

Refer to the following:
?€¢
Control Module References in Body Control System for the applicable schematic


?€¢
Testing for Intermittent Conditions and Poor Connections in Wiring Systems


?€¢
Connector Repairs in Wiring Systems

Did you find and correct the condition?
Go to Step 8
Go to Step 7

7

Important: Perform the module programming or setup procedure if required.
Replace the module that is not communicating. Refer to Control Module References in Body Control System for the appropriate Repair Instructions for the module replacement.
Did you complete the replacement?
Go to Step 10
--

8

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Select the Display DTCs function for the module which was not communicating.
Does the scan tool display any DTCs which do not begin with a "U"?
Go to Control Module References in Body Control System for applicable Diagnostic System Check
Go to Step 9

9
Use the scan tool in order to clear the DTCs.
Did you complete the action?
Go to Step 10
--

10

Select the Display DTCs function for the modules which had U1000 or U1255 set as a current DTC.
Does the scan tool display DTCs which do not begin with a "U"?
Go to Control Module References in Body Control System for applicable Diagnostic System Check
Go to Step 11

11

Use the scan tool in order to clear the DTCs.
Did you complete the action?
System OK
--

12
Did you record any other DTCs for the modules which had U1000 or U1255 set as a current DTC?
Go to
Control Module References in Body Control System for applicable Diagnostic System Check
Go to Step 13

13

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Use the scan tool in order to clear the DTCs.
  4. Turn OFF the ignition for at least 5 seconds.
  5. Turn ON the ignition with the engine OFF.
  6. Select the Display DTCs function.
Does the scan tool display U1000 or U1255 set as a current DTC?
Go to Step 14
Go to Diagnostic Aids

14
Important: Perform the module programming or setup procedure if required.
Replace the module which had U1000 or U1255 set as a current DTC. Refer to
Control Module References in Body Control System for the appropriate Repair Instructions for the module replacement.
Did you complete the replacement?
System OK

Mar 12, 2016 | 2002 Pontiac Grand Am GT1

1 Answer

2003 4500. Why have gauges stopped working?


You could have anyone of a number of different problems . I know your year vehicle falls in the range of GM instrument culster problems . There are little stepper motors ( electric motors ) that make the gauges move . There could be DTC'S - diagnostic trouble codes stored in the instrument cluster . An you have to know how the instrument cluster knows how much to move the needles on the gauges . All the input sensors to the PCM/ECM - engine computer vehicle speed sensor , fuel pressure , oil pressure , etc... All the modules on the truck are hooked together on a serial data communication network .The PCM/ECM sends this information out on the data bus for the other moduels that need the info .
Engine Oil Pressure (EOP) Gage
The IPC displays the engine oil pressure on the analog EOP gage as determined by the PCM. The PCM monitors the signal circuit of the EOP sensor. When the EOP sensor resistance is high, the engine oil pressure is high. When the EOP sensor resistance is low, the engine oil pressure is low. The IPC receives a class 2 message from the PCM indicating the engine oil pressure. The EOP gage defaults to 0 kPa (0 psi) when the following conditions occur:
• The PCM detects a malfunction in the engine oil pressure sensor signal circuit. Refer to Diagnostic System Check - Instrument Cluster .
• The IPC detects a loss of class 2 communication with the PCM.
Speedometer
The IPC displays the vehicle speed on the analog speedometer based on the vehicle speed signal from the PCM. The PCM converts the data from the vehicle speed sensor to a 4000 pulses/mile signal. The IPC uses the vehicle speed signal circuit from the PCM in order to calculate the vehicle speed.
The powertrain control module (PCM) creates the vehicle speed signal by pulsing the signal circuit to ground at a rate of 4K PPM. The instrument panel cluster (IPC) converts the 4K PPM signal to a speedometer position. The IPC also receives a class 2 message from the PCM indicating the vehicle speed. The IPC uses this class 2 message for diagnostic purposes.
There could be up to twenty different DTC'S stored ,here is an a for instance
--------------------------------------------------------------------------------
DTC B1365
The instrument panel cluster (IPC) uses the ignition 0 voltage circuit in order to supply voltage to various indicators and gages. The IPC also receives a class 2 message from the serial data gateway module (SDGM) indicating the current power mode. Your best bet would be to take your vehicle to the Dealer or an ASE certified independant repair shop .

Dec 21, 2015 | 2003 Chevrolet Express

1 Answer

Scan code U1000


That is a communication bus problem code . Are you familiar with GM class 2 serial data communication network ? All the modules on the vehicle share information an they do it by the class 2 data bus.


2 UART Class 2 Bus Configuration

Dec 05, 2015 | 2006 Chevrolet Trailblazer

1 Answer

My dash in my 2006 canyon isn't working, can't find the problem


Did you have the vehicle hooked to a factory scan tool to see if it will talk to the scan tool . Your instrument cluster is electronic an has a microprocessor inside , it is connected on the serial data communication network or bus as it is called . It's hard to find a problem when you don't know how it works >
All the gauges in the instrument cluster receive there info from the ECM - BCM engine an body computers on the data bus .
The instrument panel cluster (IPC) displays the vehicle speed based on the information from the engine control module (ECM). The IPC receives a serial data message from the BCM indicating the vehicle speed.
PRND321 Display
The instrument panel cluster (IPC) displays the selected gear position as determined by the engine control module (ECM). The IPC receives a serial data message from the ECM indicating the gear position. The PRND321 display blanks if:
?€¢
The ECM detects a malfunction in the transmission range switch circuit.


?€¢
The IPC detects a loss of serial data communications with the BCM.


?€¢
The BCM detects a loss of serial data communications with the ECM.


This you should take to a ASE qualified repair facility or the dealer ! It is possible to short out the data bus an bring down the system , meaning nothing on the vehicle will work !

Sep 24, 2015 | Cars & Trucks

1 Answer

I have a 04 tahoe and at times when i turn the ignition on the gauges don't move and when I'm driving they will jump on and off can someone explain this


If it is all the gauges , I would pull the instrument cluster an check the connections on the back of the instrument cluster . I would also check power an grounds , you would need to find a pin out chat to do this. If you don't know what that is , It's just a diagram of the connector show what each terminal is for ! Also do a wiggle test on the wiring ! Do the dash lights do the same thing ?

All the gauge settings are information determined by the PCM - engine computer , the info is sent to the instrument cluster by a serial data communication network !
Speedometer
The instrument panel cluster (IPC) displays the vehicle speed on the analog speedometer based on the vehicle speed signal from the powertrain control module (PCM). The PCM converts the data from the vehicle speed sensor to a 4,000 pulses/mile signal. The IPC uses the vehicle speed signal circuit from the PCM in order to calculate the vehicle speed.
The speedometer defaults to 0 km/h (0 mph) if a malfunction in the vehicle speed signal circuit exists.
Tachometer
The instrument panel cluster (IPC) displays the engine speed on the analog tachometer based on the engine speed signal from the powertrain control module (PCM). The IPC uses the engine speed signal circuit -- 2 pulses/engine revolution -- from the PCM in order to calculate the engine speed.
The tachometer defaults to 0 RPM if a malfunction in the engine speed signal circuit exists
Voltmeter
The instrument panel cluster (IPC) displays the system voltage as determined by the body control module (BCM). The IPC receives a class 2 message from the BCM indicating the battery voltage. When the engine is ON, the gage should be between 10-16 volts.
PRNDL Display
The instrument panel cluster (IPC) displays the selected gear position as determined by the powertrain control module (PCM). The IPC receives a class 2 message from the PCM indicating the gear position. The PRNDL display blanks if:
Fuel Gage
The instrument panel cluster (IPC) displays the fuel level as determined by the powertrain control module (PCM). The IPC receives a class 2 message from the PCM indicating the fuel level percent. The fuel gage defaults to empty if:
Engine Coolant Temperature Gage
The instrument panel cluster (IPC) displays the engine coolant temperature as determined by the powertrain control module (PCM). The IPC receives a class 2 message from the PCM indicating the engine coolant temperature. The engine coolant temperature gage defaults to 75?°C (160?°F) or below when:
?€¢
The PCM detects a malfunction in the engine coolant temperature sensor circuit.


?€¢
The IPC detects a loss of class 2 communication with the PCM.


The data link connector (DLC) allows a scan tool to communicate with the class 2 serial data line. The serial data line is the means by which the microprocessor-controlled modules in the vehicle communicate with each other. Once the scan tool is connected to the class 2 serial data line through the DLC, the scan tool can be used to monitor each module for diagnostic purposes and to check for diagnostic trouble codes (DTCs). Class 2 serial data is transmitted on a single wire at an average of 10.4 kbps. This value is an average, class 2 uses a variable pulse width modulation to carry data and depending on the message it may operate faster or slower. The bus will float at a nominal 7.0 volts during normal operation. Each module can pull this lower during the transmission. The bus is not at battery positive voltage or ground potential during normal operation. When the ignition switch is in RUN, each module communicating on the class 2 serial data line sends a state of health (SOH) message every 2 seconds to ensure that the module is operating properly. When a module stops communicating on the class 2 serial data line, for example if the module loses power or ground, the SOH message it normally sends on the data line every 2 seconds disappears. Other modules on the class 2 serial data line, which expect to receive that SOH message, detect its absence; those modules in turn set an internal DTC associated with the loss of SOH of the non-communicating module. The DTC is unique to the module which is not communicating, for example, when the inflatable restraint sensing and diagnostic module (SDM) SOH message disappears, several modules set DTC U1088. Note that a loss of serial data DTC does not normally represent a failure of the module that set it.
You may want to take this to a ASE certified repair shop or " oh no " The Chevy dealer ! I don't know why people dislike the dealer so much . I worked at one for a number of years an we had a good bunch of technicians ! No body knows your GM vehicle better !

Aug 31, 2015 | Cars & Trucks

1 Answer

U1000


it is a communication error with the ecm from the ignition switch here is the code description

GM Number U1000

Type Network - Manufacturer Controlled DTC - Manufacturer Controlled

Description Class 2 Communication Malfunction Conditions
Cause
DTC B1327, U1300, U1301 and U1305 not current (any particular device on the Class 2 serial data circuit will support some subset of these codes), the ignition switch position requires serial data communication to occur, then at least one operating parameter has not been associated with an identification number within 5 seconds after beginning serial data communication (a default value is used)

Oct 29, 2008 | 2003 Chevrolet TrailBlazer

2 Answers

I have a 2003 GMC Savana Van. The brake light came on and the brake alarm rings continously but will stop if I hit a bump (and then start again if I hit another one). I'm thinking a loose wire but several...


If someone took the time to look at the electrical schematic you will see several grounds in the circuit My first place I would go would be to check all the Grounds and Connections for the Brake Fluid level control, Brake Warning Indicator
The Instrument Panel Cluster (IPC) illuminates the brake warning indicator when one or more of the following occurs:
  • The body control module (BCM) detects that the park brake is engaged. The IPC receives a class 2 message from the BCM requesting illumination.
  • The electronic brake control module (EBCM) detects a low brake fluid condition. The IPC receives a class 2 message from the EBCM requesting illumination.
  • The electronic brake control module (EBCM) detects a closed brake pressure differential switch. The IPC receives a class 2 message from the EBCM requesting illumination.
  • The EBCM detects an ABS malfunction which disables dynamic rear proportioning (DRP) . The IPC receives a class 2 message from the EBCM requesting illumination.
  • The IPC detects a closed power brake booster alarm switch and closed power brake booster fluid flow alarm switch. The IPC illuminates the brake warning indicator and sends a class 2 message to the radio requesting the brake warning alarm.
  • The IPC performs the bulb check at the start of each ignition cycle. The brake warning indicator illuminates for approximately 3 seconds before turning OFF.
  • The IPC detects a loss of class 2 communications with the BCM or with the EBCM.
Driver Information Indicators and Messages
The following indicators are used to inform the driver of several different factors.

Brake Warning Indicator
The Instrument Panel Cluster (IPC) illuminates the brake warning indicator when the following occurs.
  • The Body Control Module (BCM) detects that the park brake is engaged. The IPC receives a serial data message from the BCM requesting illumination. The brake warning indicator flashes at a rate of approximately twice per second when the park brake is engaged.
  • The EBCM detects a low brake fluid condition or base brake pressure differential and sends a serial data message to the IPC requesting illumination.
  • The IPC performs the bulb check.
  • The EBCM detects an ABS-disabling malfunction which also disables Dynamic Rear Proportioning (DRP) and sends a serial data message to the IPC requesting illumination.

Here is a description of how the system works But i would check my Grounds and connections
www.aceautomotive1.com
Contact me if you need any more information Ill be glad to help

Aug 01, 2008 | GMC Savana Cars & Trucks

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