• 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.

For symptom byte information, refer to Symptom Byte List.

The powertrain sensor high speed GMLAN serial data circuits are serial data buses used to communicate information between the devices. If this serial data system is inoperative, the devices will still communicate with the scan tool due to other serial data systems but not with each other.

• Supply voltage to the devices are in the normal operating range.
• The vehicle power mode requires serial data communications.

The device setting the DTC has attempted to establish communications on the powertrain sensor high speed GMLAN serial data circuits more than 3 times.

• The device suspends all message transmission.
• The device uses default values for all parameters received on the serial data circuits.
• The device inhibits the setting of all other communication DTCs.

• A current DTC clears when the malfunction is no longer present.
• A history DTC clears when the device ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

• Data Communication Schematics
• Control Module References

Master Electrical Component List

Data Link Communications Description and Operation

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

Control Module References for scan tool information

1. Ignition ON/Vehicle in Service Mode.
2. Verify DTC U240E is not set.
• If DTC U240E is set

  Refer to DTC U0076 to diagnose powertrain sensor bus.

• If DTC U240E is not set
3. All OK