Question about 2003 Chevrolet Silverado 2500HD

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Engine light is on and code is u1255 class 2 communication malfunction

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Class 2 communication is 2 wire system that run to all the modules in the car ranging from mirrors to seats radio HVAC and more the malfunction occurs when one of the modules has lowered the operating voltage in the circuit . very expensive equipment needed to repair or pinpoint its location. suggest dealer repair.

Posted on Apr 17, 2014

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I have a 2003 GMC Yukon XL Denali that today all of the gauges went to zero and Odometer is out. The truck starts and drive Great.... What can cause this problem?


Only the gauges don't work ? All the warning lights come on when you turn on the key ? ABS , check engine, air bag etc... Have you had the vehicle to a repair shop to have the vehicle checked for DTC'S - diagnostic trouble codes stored in the instrument cluster ? There is a microprocessor inside the instrument cluster an can store DTC'S which have nothing to do with the check engine light . The gauges are controlled by that microprocessor based on information from the PCM ,sent on the class 2 serial data network .

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). 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.
Engine Oil Pressure Gage
The instrument panel cluster (IPC) displays the engine oil pressure as determined by the powertrain control module (PCM). The IPC receives a class 2 message from the PCM indicating the engine oil pressure. The engine oil pressure gage defaults to 0 kPa (0 psi) or below if:
• The PCM detects a malfunction in the engine oil pressure sensor circuit.
• The IPC detects a loss of class 2 communications with the PCM.
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:
• 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 a pre-determined value, the low fuel indicator illuminates.
Reviewing the fuel system description will further explain how the system functions. Refer to:
• Fuel System Description in Engine Controls - 4.8L, 5.3L and 6.0L
• Fuel System Description in Engine Controls - 8.1L

There are also U codes , communication failure's DTC U1000 and U1255

Circuit Description
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 identification number of the module which sent the message for State of Health monitoring. 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 identification number with at least one critical parameter within about five seconds of beginning serial data communication, DTC U1000 or U1255 is set. When more than one critical parameter does not have an identification number associated with it, the DTC will only be reported once. The class 2 serial data line on this vehicle is a ring/star configuration. The following modules communicate on the class 2 serial data line:
• The body control module (BCM)
• The digital audio broadcast (DAB) module
• The digital radio reciever
• The driver door module (DDM)
• The electronic brake control module (EBCM)
• The front passenger door module (FPDM)
• The HVAC control module
• The HVAC control module-rear auxilliary
• The inflatable restraint sensing and diagnostic module (SDM)
• The instrument panel cluster (IPC)
• The memory seat module (MSM)
• The powertrain control module (PCM)
• The radio
• The radio amplifier
• The rear seat audio (RSA) controller
• The rear seat entertainment (RSE) assembly w/U42
• The rear wheel steering control module
• The remote playback device-CD player w/U1S
• The suspension control module
• The transfer case shift control module
• The transmission control module (TCM) w/allison transmission
• The theft deterrent control module
• The vehicle communication interface module (VCIM) w/UE1

Your best bet would be to take it to a qualified repair shop .

Mar 23, 2017 | GMC Cars & Trucks

1 Answer

I've got a 2001 Cadillac deville and it says it's lost the IRC ID and IRC data code. any idea how that happen?


When a malfunction such as an open fuse to a module occurs while modules are communicating, a DTC U1001-1254 Loss of 000 Communications is set current. When the modules stop communicating the current DTC U1001-1254 Loss of 000 Communications is cleared but the history DTC remains. When the modules begin to communicate again, 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. Radio quit working shows Code IRC U1000 please help

Dec 07, 2016 | 2001 Cadillac DeVille

2 Answers

2001 buick century stalled without warning. tried to restart, but wouldnt crank, no fuel pump noise, no click. had power to radio, heater fan, flashers but not dashboard lights (prndl, fuel gauge).


Make sure battery has a full charge and battery connections all good. Check fusible links where applicable. Any component that doesn't work and is fuse protected, not only check the fuse, check the fuse circuit for voltage, use a test lite.
The wiring diagram is for starter circuit, you can see the fuses. Any testing for starter motor, make sure tranny is in park or neutral and parking brake is set. It is possible to jump crank relay to see if starter motor will crank, but, that doesn't mean it will start. Make sure vehicle can't move.
26366687-mcf5uwio2utwh31fa31y4rw0-1-0.jpg

26366687-mcf5uwio2utwh31fa31y4rw0-1-2.jpg

Nov 21, 2016 | 2001 Buick Century

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

I get codes or DTC's that i have no idea what would cause them? IPC 04610, IPC P1610, IPC U1255, AMC B1348, SDM U1255, IRC U1255


OBDII Code U1255 CADILLAC Lost Communications HelpForCars net P1610 Cadillac how to repair
DTC B1348 Very Low A/C Refrigerant Pressure
DTC U1255 Serial Data Line Malfunction
The class 2 serial data line communicates information between the modules. Each module connected to the serial data line is assigned a recognition code, or address. This code is used in order to identify which modules are communicating. Modules communicate with each other by periodically sending state of health (SOH) messages. When the ignition switch is in RUN, each module that is communicating on the serial data line sends an SOH message every 2 seconds. This ensures that the system is operating properly. At key on, most modules must learns the initiation data from other modules on the serial data line. When a module requests initialization data from another module, and that request is not acknowledged after 5 seconds, the module stores class 2 initialization error DTC U1255.
Conditions for Setting the DTC
?€¢
The module does not receive required initialization data on the class 2 serial data line. The module retries the request for 5 seconds, and then sets DTC U1255.


?€¢
This DTC only sets if DTC U1300 or U1301 are not current


Attempt to establish communication with all of the modules using a scan tool.
Does the scan tool communicate with all of the modules?
--
Go to Step 3
Go to the appropriate diagnostic system check for the module that is not communicating

May 12, 2015 | 1999 Cadillac DeVille

1 Answer

Fixes for non-communicating OBD II port and nonworking trunk release button on driver door panel?


What pins did your friend jump in the DLC ,2 an 4 ? they don't call it ALDL any more ! Does the vehicle start an run ?
The data link connector (DLC) is a standardized 16 cavity connector. Connector design and location is dictated by an industry wide standard, and is required to provide the following:
?€¢
Scan tool power battery positive voltage at terminal 16.


?€¢
Scan tool power ground at terminal 4.


?€¢
Common signal ground at terminal 5.


?€¢
Class 2 signal at terminal 2.


I wonder how many friends out there mess up other friends vehicles from stuff they see on the internet . When are you people going to learn , your messing with complex electronics !!!!! He shorted out the class 2 serial data communication network !
Do you know what this is ? if not you need to take to your local GM Mr. goodwrench !
Class 2 Serial Data Link
The data link is configured as a ring with discrete lines entering and leaving each module. This allows communications to the modules on the ring if one of the two discrete circuits is open.
A total list of the control modules on the Class 2 Serial Data Line can include the following:
?€¢
Dash Integration Module (DIM)


?€¢
Driver Door Module (DDM)


?€¢
Electronic Brake Control Module (EBCM)


?€¢
Head Up Display (HUD) w/UV6


?€¢
HVAC Control Module w/C67


?€¢
Inflatable Restraint Sensing and Diagnostic Module (SDM)


?€¢
Instrument Panel Cluster (IPC)


?€¢
Instrument Panel Integration Module (IPM) w/CJ2


?€¢
Memory Seat Module (MSM) w/A45


?€¢
Powertrain Control Module (PCM)


?€¢
Radio


?€¢
Rear Integration Module (RIM)


?€¢
Remote Control Door Lock Receiver (RCDLR)


?€¢
Remote Playback Device - CD Changer w/U1S


?€¢
Theft Deterrent Control Module


?€¢
Vehicle Interface Unit (VIU) w/UE1


Power door serial data does not communicate with the scan tool via the DLC. Power door serial data information is interpreted by the driver door module (DDM) and transmitted on the Class 2 data link by the DDM.
Power door serial data is used for serial data communication between the four door modules as well as the driver door switch assembly (DDSA
Scan Tool Does Not Communicate with Class 2 Device
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. Connecting a scan tool to the DLC allows communication with the modules for diagnostic purposes.
The engine will not start when there is a total malfunction of the class 2 serial data circuit while the engine is not running.
Test Description
The numbers below refer to the step numbers on the diagnostic table.

  1. A partial malfunction in the class 2 serial data circuit uses a different procedure from a total malfunction of the class 2 serial data circuit.

  2. The DTC U1300, U1301, and U1305 may be retrieved with a history status. These DTCs are not the cause of the present condition.

  3. A State of Health DTC with a history status may be present along with a U1000 or a U1255 with a current status. This indicates that the malfunction occurred when the ignition was on.

Apr 22, 2015 | 2001 Buick LeSabre

1 Answer

Most of the warning lights and fuel gauge does not operate when the ignition switch is turned to on.


Given the complexity of your vehicle , all the control modules , serial data communication network. Having the vehicle scanned for DTC'S - diagnostic trouble codes , not a code reader or at a auto parts store . A professional type tool is need to pull codes from BCM - body computer , Instrument cluster .

Fuel Gage
The IPC displays the fuel level as determined by the PCM. The body control module (BCM) receives a class 2 message from the PCM indicating the fuel level percent. The BCM converts the fuel level percent into a percent gage deflection. The IPC receives a message from the BCM via the serial peripheral interface (SPI) indicating the requested gage position. The fuel gage defaults to E (empty) if:
• The PCM detects a malfunction in the fuel level sensor circuit.
• The BCM detects a loss of class 2 communications with the PCM.
• The IPC detects a loss of SPI communications with the BCM.
When the fuel level is less than a pre-determined value, the low fuel indicator illuminates.

Could have U- codes , communication network problems .

DTC U1000 and U1255

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.

Mar 08, 2017 | 2003 Chevrolet Malibu

1 Answer

2003chevy express 3500 W/6.0 cable throttle. Trouble codes U1000,U1016,U1041. Instrument cluster drops off,(gauges go dead) EBS light stays on,security lights also. Van had a remote starter alarm system...


U codes pertain to the class 2 serial data network . A dead module ,a short on the network will bring down the network - no communications between modules = no start problems .
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 identification number of the module which sent the message for State of Health monitoring. 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 identification number with at least one critical parameter within 5 seconds of beginning serial data communication, DTC U1000 or U1255 DTC is set. When more than one critical parameter does not have an identification number associated with it, the DTC will only be reported once. The class 2 serial data line on this vehicle is a star configuration. The following modules communicate on the class 2 serial data line:
• The body control module (BCM)
• The electronic brake control module (EBCM)
• The inflatable restraint sensing and diagnostic module (SDM)
• The instrument panel cluster (IPC)
• The powertrain control module (PCM)
• The radio
• The remote control door lock receiver (RCDLR)
• The vehicle communication interface module (VCIM)

Look's like a communication problem with the PCM & EBCM !
Powertrain Control Module (PCM)
U1016
Electronic Brake Control Module (EBCM)
U1041
Diagnostic Aids
• An intermittent open between a module and a star connector may cause this DTC to set.
• A poor connection at a module or a star connector may cause this DTC to set.
• An intermittent open in a star connector may cause this DTC to set.
• An open voltage or ground circuit to a module may cause this DTC to set.
• An internal module malfunction may cause this DTC to set.


012 GM Class II Communications

May 12, 2017 | Chevrolet Cars & Trucks

1 Answer

1998 Cadillac STS with IPM U1255 code history. what does this code mean?


U1255 - Class 2 Communication Malfunction (Serial Data Line Malfunction)

here is a link to all of the codes for your caddy
http://myweb.accessus.net/~090/dtcobd2n.html#net

Aug 20, 2009 | 1998 Cadillac Seville

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