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U0209



DTC U0100 - U02FF

DTC DESCRIPTOR

DTC U0100 00
Lost Communication With Engine/Powertrain Control Module (ECM/PCM)

DTC U0101 00
Lost Communication With Transmission Control Module (TCM)

DTC U0121 00
Lost Communication With Electronic Brake Control Module (EBCM)

DTC U0140 00
Lost Communication With Body Control Module (BCM)

DTC U0151 00
Lost Communication With Sensing and Diagnostic Module (SDM)

DTC U0155 00
Lost Communication With Instrument Panel Cluster (IPC) Control Module

DTC U0164 00
Lost Communication With HVAC Control Module

DTC U0168 00
Lost Communication With Vehicle Theft Deterrent (VTD) Control Module

DTC U0170 00
Lost Communication With Passenger Presence System (PPS)

DTC U0184 00
Lost Communication With Radio

DTC U0186 00:
Lost Communication With Audio Amplifier

DTC U0194 00
Lost Communication With Digital Radio Receiver (DRR)

DTC U0198 00
Lost Communication With Communication Interface Module (OnStar(R))

DTC U0209 00
Lost Communication With Heated Seat Module (HSM)

DTC U0214 00
Lost Communication With Remote Function Actuator (RFA)

DIAGNOSTIC FAULT INFORMATION




Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview

CIRCUIT/SYSTEM DESCRIPTION
Modules connected to the high and low speed GMLAN serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. The modules have prerecorded information about what messages are needed to be exchanged on the serial data circuits, for each virtual network. The messages are supervised and also, some periodic messages are used by the receiver module as an availability indication of the transmitter module. Each message contains the identification number of the transmitter module.

The body control module (BCM) activates the high speed communication enable and the accessory voltage signal circuits by applying voltage when the ignition key is in ACC, ON or START. The high speed communication enable circuit wakes up the electronic brake control module (EBCM) for bus communication and the accessory voltage signal circuit wakes up the engine control module (ECM) and transmission control module (TCM)

CONDITIONS FOR RUNNING THE DTC
- The system voltage is between 9-16 volts.
- The vehicle power mode requires serial data communication to occur.

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
The module(s) is never signaled, therefore the specific subsystem(s) will not function.

CONDITIONS FOR CLEARING THE DTC
- A current DTC clears when the malfunction is no longer present.
- A history DTC clears when the module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.

DIAGNOSTIC AIDS
- Use the DTC Descriptor list above to determine the module which is not communicating.

- If there are multiple non-communicating modules choose the one closest to the data link connector (DLC).

- Use Data Link References to determine if the module uses high or low speed GMLAN serial data communications. Initial Inspection and Diagnostic Overview

- Some modules may not have internal protection for specific voltage outputs and may open a battery positive voltage or ignition voltage source fuse. If a voltage input fuse is open and no short is found in that circuit, ensure that no module output voltage circuit is shorted to ground before replacing the module.

- This diagnostic can be used for any module that should communicate with high or low speed GMLAN serial data providing the vehicle is equipped with the option that uses that module.

Reference Information

Schematic Reference
• Data Link Connector Schematics Electrical Diagrams
• Control Module References Control Module References

Connector End View Reference
Vehicle Connector Views Connector Views

Electrical Information Reference
• Circuit Testing Circuit Testing
• Connector Repairs Connector Repairs
• Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs Wiring Repairs

CIRCUIT/SYSTEM TESTING
1. Using the DTC Descriptor and Diagnostic Aids above, determine the module that is not communicating that should be tested.

2. Ignition OFF, disconnect the harness connector of the module that is not communicating.

3. Ignition ON, verify that a test lamp illuminates between the high speed communication enable circuit OR the accessory voltage signal circuit and ground.
- If the test lamp does not illuminate, repair the circuit for an open/high resistance. If the circuits test normal, replace the BCM.

IMPORTANT: Only the high speed GMLAN modules have a the high speed communication enable circuit OR the accessory voltage signal circuit. Refer to the module schematics to identify which modules have these circuits. If the module that is not communicating does not have one of these circuits, proceed to step 4.

4. Ignition ON, verify that a test lamp illuminates between all battery positive voltage circuits and ground.
- If the test lamp does not illuminate, repair the circuit for a short to ground or an open/high resistance. If the circuit fuse is open, also test the positive voltage outputs of the module for a short to ground. If the circuits test normal, replace the faulty module.

5. Verify that a test lamp illuminates between all ignition voltage circuits and ground.
- If the test lamp does not illuminate, repair the circuit for a short to ground or an open/high resistance. If the circuit fuse is open, also test the positive voltage outputs of the module for a short to ground. If the circuits test normal, replace the faulty module.

6. Test for less than 1.0 ohm of resistance between the module ground circuits and ground.
- If greater than 1.0 ohm, repair the ground circuit for an open.

7. Use Data Link References to determine if the non-communicating module should use low speed GMLAN serial data.
- If the module is GMLAN high speed only, replace the module.

8. Test for less than 1.0 ohm of resistance in the low speed GMLAN serial data circuit between the non-communicating module and the module that displays the DTC.
- If greater than 1.0 ohm of resistance, test the low speed GMLAN serial data circuit for open/high resistance.

9. If all circuits test normal, replace the module that is not communicating.

REPAIR INSTRUCTIONS
Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests
- Control Module References for module replacement, setup, and programming
- GMLAN Wiring Repairs. GMLAN Wiring Repairs
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