Chevrolet Trax: DTC U1814: Powertrain wake-up communication circuit

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 Descriptor

DTC U1814

Powertrain Wake-Up Communication Circuit

For symptom byte information, refer to Symptom Byte List .

Diagnostic Fault Information

Circuit/System Description

The body control module (BCM) activates the ignition circuit, when the ignition key is in ACC, ON or START.

The ignition circuit wakes up the devices for serial data bus communication.

Conditions for Running the DTC

• The system voltage is between 9-16 V.
• The vehicle power mode master requires serial data communication to occur.

Conditions for Setting the DTC

The BCM senses a short to ground on the ignition circuit.

Action Taken When the DTC Sets

• The output command is turned off while the malfunction is present.
• The devices use a default value for the missing parameters until the next ignition cycle.
• The device(s) is never signaled. Therefore, the specific subsystem(s) will not function.
• The vehicle will not start while the circuit is shorted to ground.

Conditions for Clearing the DTC

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 of 50, without a repeat of the malfunction.

Reference Information

Schematic Reference

• Data Communication Schematics (Encore), Data Communication Schematics (Trax)
• Control Module References

Connector End View Reference

WIRING SYSTEMS AND POWER MANAGEMENT - COMPONENT CONNECTOR END VIEWS - INDEX - ENCORE WIRING SYSTEMS AND POWER MANAGEMENT - COMPONENT CONNECTOR END VIEWS - INDEX - TRAX

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

NOTE: Use the schematic to determine which devices are on the K9 Body Control Module's ignition circuit terminal 22 X4. Use the connector end view to identify the ignition circuit terminal for each of those devices.

1. Ignition OFF, disconnect the harness connectors at an easily accessible device that shares the K9 Body Control Module's ignition circuit terminal 22 X4. Ignition ON.
2. Verify that the DTC U1814 remains current.

If the DTC becomes history

Replace the device that was just disconnected.

If the DTC remains current

3. With the prior devices disconnected, repeat steps 1 and 2 for each device on the ignition circuit except the K9 Body Control Module.
4. Ignition OFF, disconnect the X4 harness connector at the K9 Body Control Module.
5. Test for infinite resistance between the ignition circuit terminal 22 X4 at the K9 Body Control Module and ground.

If less than infinite resistance

Repair the short to ground on the circuit.

If infinite resistance

6. Replace the K9 Body Control Module.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• GMLAN and Media Oriented Systems Transport (MOST) Wiring Repairs
• Control Module References for device replacement, programming and setup

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