GM Service Manual Online
For 1990-2009 cars only

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 Module

Diagnostic 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

Data Communication Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Data Link Communications Description and Operation

Electrical Information Reference

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

Scan Tool Reference

Control Module References for Scan Tool Information

Circuit/System Testing

  1. Ignition OFF, disconnect the harness connector at the DRM.
  2. Ignition OFF, test for less than 5.0 Ω between the ground circuit terminal A1 and ground.
  3. If greater than the specified range, test the ground circuit for an open/high resistance.
  4. Ignition ON, verify a test lamp illuminates between the B+ circuit terminal A7 and ground.
  5. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
  6. Ignition ON, verify a test lamp illuminates between the ignition voltage circuit terminal B12 and ground.
  7. If the test lamp does not illuminate, test the ignition voltage circuit for a short to ground or an open/high resistance.
  8. Ignition OFF, test for more than 100 Ω between the serial data circuits terminals B9 and A2.
  9. 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.
  10. If all circuits test normal, replace the DRM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

Control Module References for DRM replacement, setup, and programming