Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
DTC Descriptors
DTC U0294: Lost Communication with Powertrain Control Monitor ModuleDiagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage |
|---|---|---|---|
B+ | U0294 | U0294 | -- |
Ignition+ | U0294 | U0294 | -- |
High Speed GMLAN Serial Data (+) | 1 | U0294 | 1 |
High Speed GMLAN Serial Data (-) | 1 | U0294 | 1 |
Ground | -- | U0294 | -- |
1. Scan Tool Does Not Communicate With High Speed GMLAN Device | |||
Circuit/System Description
When activated, the data recorded module (DRM) records all of the high speed GMLAN serial data message activity on the bus.
Conditions for Running the DTC
The system voltage is between 9-16 volts.
Conditions for Setting the DTC
| • | The DTC will set when there is an open/high resistance, short to ground, or short to voltage in the high speed GMLAN serial data circuits. |
| • | The DTC will set when there is an open/high resistance or short to ground in the B+ or ignition circuit to the module. |
| • | The DTC will set when there is an open/high resistance in the ground circuit to the module. |
Action Taken When the DTC Sets
The DRM will not record the high speed GMLAN serial data messages.
Conditions for Clearing the DTC
The current DTC will clear when the malfunction is no longer present.
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Data Link Communications Description and Operation
Electrical Information Reference
| • | Circuit Testing |
| • | Wiring Repairs |
Scan Tool Reference
Control Module References for Scan Tool Information
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the DRM.
- Ignition OFF, test for less than 5.0 Ω between the ground circuit terminal A1 and ground.
- Ignition ON, verify a test lamp illuminates between the B+ circuit terminal A7 and ground.
- Ignition ON, verify a test lamp illuminates between the ignition voltage circuit terminal B12 and ground.
- Ignition OFF, test for more than 100 Ω between the serial data circuits terminals B9 and A2.
- If all circuits test normal, replace the DRM.
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
| ⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. |
| ⇒ | If the test lamp does not illuminate, test the ignition voltage circuit for a short to ground or an open/high resistance. |
| ⇒ | If greater than the specified range, test the serial data circuits for an open/high resistance between the DRM and a module setting the DTC or a serial data splice pack. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the repair.
Control Module References for DRM replacement, setup, and programming
