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Read this, it might help:
http://www.iatn.net/forums/2/317236/what-would-you-do-no-communication-with-bcm

Posted on Nov 27, 2014

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Some lights stay on when the key is removed like the gear indicator light. What can cause this and can I add a battery toggle so I dont have to disconnect the battery every time I leave the car


I wouldn't do that given the complexity of electronic modules an data bus communication networks on this vehicle . Disconnecting batteries can cause modules to go to sleep an not wake back up . The ignition switch is an input to the BCM - body control module , the BCM turns on relays powering up systems on the vehicle .
The BCM executes the high power mode by grounding the controlled power relay coil control circuit of the CONTROLLED POWER relay whenever the BCM is awake. This circuit also is grounded for 15 minutes after you turn the ignition switch to the LOCK position in order to obtain the RAP function. After 15 minutes elapse, the BCM enter a sleepstate and transitions to the low power mode. The components under controlled power then receive any necessary voltage from the battery positive voltage circuit of the BCM. If the BCM is in the low power mode, and the BCM detects that the current exceeds approximately 2 amperes, the BCM wakes up and re-enters the high power mode. If the vehicle remains inactive with the ignition in the LOCK position and without any BCM wake-ups for a period of 3 days, the BCM deactivates the low power mode. The following components are under controlled power: There are probably DTC'S - diagnostic trouble codes stored in the BCM . A simple code reader can not read these , an has nothing to do with the check engine light . Battery Disconnect or Replacement Problems You may have been lucky so far disconnecting the battery .

Sep 14, 2016 | 2001 Cadillac Eldorado

1 Answer

Where is the Body Control Module located?


I'm just curious if your aware of the BCM function's on your vehicle an if you know what the gate way module is ? An do you know about serial data communication between modules ? An do you know what the power mode master is ? And do you know the BCM needs programming ?
The body control module (BCM) in this vehicle functions as a gateway or translator. The purpose of the gateway is to translate serial data messages between the GMLAN high speed buss and the GMLAN low speed buss for communication between the various modules. The gateway will interact with each network according to that network's transmission protocol.
One example of this necessary communication is the communication between the engine control module (ECM)/powertrain control module (PCM) which is high speed serial data and Theft Deterrent Module which is low speed serial data. If these modules can not exchange information, the vehicle will not start.
Communication between the BCM and a scan tool can be on the high speed GMLAN network or low speed GMLAN network. If one network is lost, the BCM can still communicate with the scan tool. A lost communication DTC typically is set in modules other than the module with a communication failure.

Mar 04, 2016 | 2007 GMC Yukon XL Denali

1 Answer

Why would electric door locks, interior lights trunk light and rear defroster not work


this could indicate a bad BCM causing these problems. you should go to a shop and have it checked out for a BCM problem or communication problem.

Oct 11, 2014 | Cars & Trucks

1 Answer

U110C lost fuel level message. is this something to do with the pcm


Hi Anonymous, Im glad to help!

The U110C is a BUS Message and usually has to do with both PCM and BCM, because its a lose of BUS Signal between the PCM and the BCM.

FIRST THING TO TRY:
The first thing I would try is remove the negative battery cable for 20 seconds then replace it. NEXT: Start the engine several times then let idle for 10 to 20 minutes then start it several more times and if the code doesn't return and the check engine light stays out, simple drive it for awhile like you normally would. If the code come right back, below is some common problems.

COMMON CAUSES of U110C:
(1) Communication with BCM is lost / See if you can communicate with the BCM.
(2) PCI Bus Circuit open between PCM and BCM / Check the positive and negative bus signal at both the PCM and BCM.
(3) BCM
(4) PCM
(5) Fuel Level Bus Message is missing

Obviously, all these issues must be tested to see which one is causing the problem. BUT first try the battery cable removal and see what happens.

Let me know the out come and I'll try to help further.
Hope this helps and have an awesome day!

Sep 28, 2014 | 2005 Chrysler Pacifica

1 Answer

The lights inside my car and wipers go on and off and the locks and unlock all this happens when I open the door to the car, it's a 2005 dodge grand caravan


this sounds like you may have a problem with the BCM that controls body systems. check to see if there are any codes in the BCM as this will help to find the problem. be aware that it could be a communication problem with other modules on the vehicle and the BCM causing this.

Aug 26, 2014 | 2005 Dodge Caravan

1 Answer

I have a 2003 Malibu, 3.1 V6, 120K miles. Normally when I turn the ignition switch to on, all indicator warning lights and gas gauge work in the ip cluster. After a few seconds only the battery, check...


Well Gary , you should have it checked for DTC'S - diagnostic trouble codes . Not at a part's store , thier diagnostic tool only checks engine computer codes ! Your vehicle has a number of control modules , PCM/ECM - engine , BCM - body , ABS , Air bag , the instrument cluster has a microprocessor inside , an can set DTC'S as well. But the only way to read codes in most of these modules is with a professional type scan tool . The warning lights come on when you turn the key on as a bulb check an to let you know those systems are functioning . Could be your instrument cluster is defective or a communication network problem , do you know what a serial data bus or communication network is ? This is what the control modules share information on . Your 03 chevy has the IPC bus for data transfer from the BCM to the IPC . U codes are communication error codes .

Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
U2000
The IPC determines that the BCM transmitted data to the IPC is invalid for greater than 12 seconds. The IPC sends a message to the BCM via the SPI serial data in circuit indicating that invalid data was received.
U2001
The BCM determines that the IPC transmitted data to the BCM is invalid for greater than 5 seconds.
U2002
The BCM detects that the SPI serial data in circuit is less than 1.2 v for greater than 5 seconds.
U2003
The BCM detects that the SPI serial data in circuit is greater than 4.5 v for greater than 5 seconds.
U2004
The BCM detects that the SPI serial data out circuit is less than 1.2 v for greater than 5 seconds.
U2005
The BCM detects that the SPI serial data out circuit is greater than 4.5 v for greater than 5 seconds.
U2006
The BCM detects that the SPI serial data clock circuit is less than 1.2 v for greater than 5 seconds.
U2007
The BCM detects that the SPI serial data clock circuit is greater than 4.5 v for greater than 5 seconds.

Your vehicle also uses class 2 data bus .

Class 2 Serial Data Link
The class 2 serial data link allows the following modules to communicate with each other:
• The body control module (BCM)
• The electronic brake control module (EBCM)
• The integrated radio chassis (IRC)
• The powertrain control module (PCM)
• The Remote Control Door Lock Receiver (RCDLR)
• The inflatable restraint sensing and diagnostic module (SDM)
The class 2 serial data link allows a scan tool to communicate with the above modules for diagnostic and testing purposes.

Mar 08, 2017 | 2003 Chevrolet Malibu

1 Answer

What causes obd code u110c


Read this please:

The BCM then puts the fuel level info out on the communications bus for interested modules. The PCM isn't getting the message and is turning on the MIL and setting a 'lack of communication' fault code (U110C).

Jan 13, 2013 | Cars & Trucks

1 Answer

What causes obd code u110c


U110C-NO FUEL LEVEL BUS MESSAGE
When Monitored and Set Condition:
U110C-NO FUEL LEVEL BUS MESSAGE
When Monitored: Ignition on.
Set Condition: No fuel level BUS messages received by the PCM for 20 seconds.
POSSIBLE CAUSES
DTC RESET
COMMUNICATE WITH BCM
FUEL LEVEL BUS MESSAGE
PCI BUS CIRCUIT OPEN FROM PCM TO BCM
BCM
TEST ACTION APPLICABILITY
1 NOTE: If a fuel level circuit or performance DTC is set along with P1681,
diagnose the circuit/performance DTC before continuing.
Turn the ignition on.
With the DRBIIIt, erase DTCs.
Start the engine on and off several times. Leave the engine running for at least 20
second each time.
With the DRBIIIt, read DTCs.
Does the DTC reset?
All
Yes ! Go To 2
No ! Refer to the INTERMITTENT CONDITION symptom in the
Driveability category.
Perform POWERTRAIN VERIFICATION TEST VER - 1 - NGC.
2 Ignition on, engine not running.
With the DRBIIIt, attempt to communicate with the BCM.
Can communication be established with the BCM?
All
Yes ! Go To 3
No ! Refer to the Communication Category and perform the appropriate
symptom related to no communication with BCM.
Perform POWERTRAIN VERIFICATION TEST VER - 1 - NGC.
3 Turn the ignition on.
Using the DRBIIIt, read the Fuel Level parameter in the PCM.
Does the DRBIIIt display a fuel level value?
All
Yes ! Replace and program the Powertrain Control Module in accordance
with the Service Information.
Perform POWERTRAIN VERIFICATION TEST VER - 1 - NGC.
No ! Go To 4
287
DRIVEABILITY - NGC
TEST ACTION APPLICABILITY
4 Turn the ignition off.
Disconnect the PCM harness connectors.
Disconnect the BCM harness connector.
CAUTION: DO NOT PROBE THE PCM HARNESS CONNECTORS. PROBING
THE PCM HARNESS CONNECTORS WILL DAMAGE THE PCM TERMINALS
RESULTING IN POOR TERMINAL TO PIN CONNECTION. INSTALL
MILLER SPECIAL TOOL #8815 TO PERFORM DIAGNOSIS.
Measure the resistance of the PCI Bus circuit from the BCM harness connector to the
appropriate terminal of special tool #8815.
Is the resistance below 5.0 ohms?
All
Yes ! Replace BCM in accordance with the Service Information.
Perform POWERTRAIN VERIFICATION TEST VER - 1 - NGC.
No ! Repair the PCI Bus circuit between the PCM and the BCM for an
open.
Perform POWERTRAIN VERIFICATION TEST VER - 1 - NGC
__________________

Jan 13, 2013 | 2006 Dodge Caravan

1 Answer

Headlights will not stay on, replaced switch, problem still exist


Hi Carol,

I'm not surprised that replacing the light control switch did not fix your problem.

Your headlamps are controlled by your Body Control Module (BCM).
My recommendation is to scan your BCM for possible fault codes that may lead you to the actual CAUSE of the problem. There is most likely an intermittent open circuit or a network communications fault that is causing your lights to turn off.

Oct 30, 2011 | 2004 Chevrolet TrailBlazer

1 Answer

2007 GMC Yukon wont start....


Ok supper Dave , let's get this stright , when you turn the key to start the vehicle , what happens ? The starter spins the engine or doesn't spin the engine ? This would be a no crank no start condition . if the engine does spin an doesn't start an run this is a crank no start condition . Now which is it ? The factory radio is hooked to the serial data communication network , did you or who ever installed the aftermarket radio use a interface module ? Are you familiar with the electronics on this vehicle ? BCM - body control module , low current inputs from the ignition switch which determine what mode to put the vehicle in ?

Case 4 Data Bus Issues

The body control system consists of the body control module (BCM), communications, and various input and outputs. Some inputs, outputs and messages require other modules to interact with the BCM. The BCM also has discrete input and output terminals to control the vehicle's body functions. The BCM is wired to the GMLAN high speed serial data buss and the GMLAN low speed serial data buss and acts as a gateway between them. If the BCM does not communicate the vehicle will not start due to the inability of the engine control module (ECM)/powertrain control module (PCM) and theft deterrent module (TDM) to communicate without the BCM providing the gateway function.

Power Mode Master
This vehicles body control module (BCM) functions as the power mode master (PMM). The ignition switch is a low current switch with multiple discrete ignition switch signals to the PMM for determination the power mode that will be sent over the serial data circuits to the other modules that need this information, and so the PMM will activate relays and other direct outputs of the PMM as needed. Refer to Power Mode Description and Operation for a complete description of power mode functions.

Sorry but I am a GM Tech . have been for over thirty years , Cadillac , Buick an Chevy .audio buds think it's something else. Your audio buds don't have a clue ? When change something you better well know what your messing with. .

Apr 11, 2017 | 2007 GMC Yukon

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