Good evening,
Below, I listed possible failures for the 109 code. it is a communication issue with the BCM.
When the truck shuts off, does it start right back up or does it have a long crank time? It could be a crank sensor or the fuel pump itself.
https://www.2carpros.com/articles/engine-stalls
Roy
U0109
Descriptor
Without Rpo Hp2
Probable Causes
Accessory Wake Up Serial Data Circuit Open or High Resistance
B+ Circuit Open or High Resistance
B+ Circuit Short to Ground
Body Control Module (BCM)
Control Module
High Speed GMLAN Serial Data (+) Circuit Open or High Resistance
High Speed GMLAN Serial Data (-) Circuit Open or High Resistance
Ignition Circuit Open or High Resistance
Ignition Circuit Short to Ground
Low Speed GMLAN Serial Data Circuit Open or High Resistance
Serial Data Communication Enable Circuit Open or High Resistance
this is a description of the code as well.
Circuit/System Description
The serial data circuit is the means by which the control modules in the vehicle communicate with each other. Once the scan tool is connected to the serial data circuit through the DLC, the scan tool can be used to monitor each control module for diagnostic purposes and to check for diagnostic trouble codes (DTCs). When the ignition switch is in RUN, each control module communicating on the serial data circuit sends a state of health (SOH) message to ensure that the control module is operating properly. When a control module stops communicating on the serial data circuit, for example if the module loses power or ground, the SOH message it normally sends on the serial data circuit disappears. Other control modules on the serial data circuit, which expect to receive that SOH message, detect its absence; those control modules in turn set a DTC associated with the loss of SOH of the non-communicating control module. The DTC is unique to the control module which is not communicating and one or more control modules may set the same exact code. A loss of serial data communications DTC does not represent a failure of the control modules that contain the stored code.
Conditions for Running the DTC
The system voltage is between 9-16 V.
Conditions for Setting the DTC
A supervised periodic message that includes the transmitter module availability has not been received.
Action Taken When the DTC Sets
Specific subsystems will not function.
DTC U0100 in the TCM will cause the transmission to go into default gears.
Both DTC U0100 in the TCM and DTC U0101 in the ECM will cause the malfunction indicator lamp (MIL) to illuminate.
Conditions for Clearing the DTC
The ECM/TCM turns OFF the MIL after 4 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC clears when the malfunction is no longer present.
A history DTC clears when the control module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.
Diagnostic Aids
Sometimes, while diagnosing a specific customer concern or after a repair, you may notice a history U-code present. However, there is no associated current or active status. Loss-of- communication U-codes such as these can set for a variety of reasons. Many times, they are transparent to the vehicle operator and technician, and/or have no associated symptoms. Eventually, they will erase themselves automatically after a number of fault-free ignition cycles. This condition would most likely be attributed to one of these scenarios:
- A control module on the data communication circuit was disconnected while the communication circuit is awake.
- Power to one or more control modules was interrupted during diagnosis.
- A low battery condition was present, so some control modules stop communicating when battery voltage drops below a certain threshold.
- Battery power was restored to the vehicle and control modules on the communication circuit did not all re-initialize at the same time.
- If a loss-of-communication U-code appears in history for no apparent reason, it is most likely associated with one of the scenarios above. These are all temporary conditions and should never be interpreted as an intermittent fault, causing you to replace a part.
A control module may have a U-code stored in history that does not require any repairs. Issues with late or corrupted messages between control modules can be temporary with no apparent symptom or complaint; this does not mean the control module is faulty. Do not replace a control module based only on a history U-code.
Do not replace a control module reporting a U-code. The U-code identifies which control module needs to be diagnosed for a communication issue.
Communication may be available between the BCM and the scan tool with either the low or high speed GMLAN serial data system inoperative. This condition is due to the BCM using both the low and high speed GMLAN systems.
Use Data Link References to determine if the control module uses high or low speed GMLAN serial data communications.
Some control modules may not have internal protection for specific control circuits and may open a B+ or ignition fuse. If a fuse is open and the B+ or ignition circuit is not shorted to ground, ensure none of the control circuits are shorted to ground before replacing the control module.
Some intermittent communication concerns may be caused by fretting corrosion on the serial data circuit terminals. Inspect all connectors at the control module that set the communication DTC, the control module that the communication DTC was set against, and any inline harness connectors between the two control modules. Do not replace a control module based only on fretting corrosion. Refer to bulletin 09-06-03-004 for assistance with the diagnosis and repair of this condition.
Multiple control modules may not communicate due to the serial data circuits being shorted, faulty terminating resistor, corrosion or poor connections in various control module connectors or inline connectors. Refer to bulletin 08-07-30-021 for assistance with the diagnosis and repair of these conditions, if applicable.
This diagnostic can be used for any control module that is not communicating, regardless of the type of serial data circuit it is connected to, providing the vehicle is equipped with the control module.
Reference Information
Schematic Reference
Data Communication Schematics See: Information Bus > Electrical
Control Module References See: Vehicle > Programming and Relearning > Control Module References
Connector End View Reference
Component Connector End Views See: Vehicle > Connector Views
Description and Operation
Data Link Communications Description and Operation See: Information Bus > Description and Operation
Electrical Information Reference
Circuit Testing See: Vehicle > Component Tests and General Diagnostics > Circuit Testing
Connector Repairs See: Vehicle > Component Tests and General Diagnostics > Connector Repairs
Testing for Intermittent Conditions and Poor Connections See: Vehicle > Component Tests and General Diagnostics > Testing for Intermittent Conditions and Poor Connections
Wiring Repairs See: Vehicle > Component Tests and General Diagnostics > Wiring Repairs
Scan Tool Reference
Control Module References See: Vehicle > Programming and Relearning > Control Module References for scan tool information
Circuit/System Verification
Verify that DTC U0073, U2100, U0074, U1814, U2099, B1428, B1370, B1380, B1440, or B1441 is not set.
-> If any of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle See: A L L Diagnostic Trouble Codes ( DTC ) > Diagnostic Trouble Code Descriptions > Diagnostic Trouble Code (DTC) List - Vehicle.
Circuit/System Testing
Note: Use the schematic to identify the following:
Control modules the vehicle is equipped with
Control module locations on the low and high speed GMLAN serial data circuits
The control modules B+, ignition, ground, communication enable and serial data circuit terminals
1. Determine the control module that is not communicating. Refer to Control Module U Code List.
2. Ignition OFF, disconnect the harness connector of the control module that is not communicating.
3. Test for less than 10 ohm between each ground circuit terminal and ground.
-> If greater than the specified range, test the ground circuit for an open/high resistance.
4. If equipped, verify that a test lamp illuminates between each B+ circuit terminal and ground.
-> If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test the control circuits of the control module for a short to ground. If the circuits test normal, replace the control module.
5. If equipped, ignition ON, verify that a test lamp illuminates between each ignition circuit terminal and ground.
-> If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit fuse is open, test the control circuits of the control module for a short to ground. If the circuits test normal, replace the control module.
Note: Only the high speed GMLAN modules have a serial data communication enable circuit OR an accessory wakeup serial data circuit, and the BCM is the output for these circuits. Refer to the module schematics to identify which modules have these circuits.
6. If equipped, ignition ON, verify that a test lamp illuminates between the communication enable circuit terminal OR the accessory wakeup circuit terminal and ground.
-> If the test lamp does not illuminate, test the circuit for an open/high resistance. If the circuits test normal, replace the BCM.
7. Ignition OFF, all access doors closed, all vehicle systems OFF, and key out of ignition switch. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 5 ohm between the serial data circuit terminals and the appropriate DLC terminal listed below:
Class 2 serial data circuit terminal 2
Low speed GMLAN serial data terminal 1
High speed GMLAN serial data terminal 6 or 14
-> If greater than the specified range, test the serial data circuit for an open/high resistance between the non communicating control module and a control module setting the DTC or a serial data splice pack.
8. If all circuits test normal, replace the control module that is not communicating.
Repair Instructions
Perform the Diagnostic Repair Verification See: Vehicle > Initial Inspection and Diagnostic Overview > Diagnostic Repair Verification after completing the diagnostic procedure.
GMLAN Wiring Repairs See: Vehicle > Component Tests and General Diagnostics > GMLAN Wiring Repairs
Control Module References See: Vehicle > Programming and Relearning > Control Module References for control module replacement, setup, and programming
Thursday, September 3rd, 2020 AT 11:45 AM
(Merged)
