C126D

DTC C126C, C126D, C12E3, or U180F

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructionsprovides an overview of each diagnostic category.

DTC Descriptors
DTC C126C
- Control Module Communication Bus B Off

DTC C126D
- Control Module Communication Bus B Off

DTC C12E3
- Control Module Communication Bus B Off

DTC U180F
- Control Module Communication Bus B Off

Circuit/System Description

The PTLAN serial data circuits are serial data buses used to communicate information between the control modules. The PTLAN serial data circuits also connect directly to the data link connector (DLC) for programming purposes. If this serial data system is inoperative the modules will still communicate with the scan tool due to other serial data systems but not with each other. Communication with the scan tool for the modules on the PTLAN bus is through the serial data gateway module (SDGM) on the HSGMLAN serial data system.

Conditions for Running the DTCs

* Supply voltage to the modules are in the normal operating range.
* The ignition switch in any position other than START.

Conditions for Setting the DTC

The module setting the DTC has attempted to establish communications on the PTLAN serial data circuits more than 3 times.

Action Taken When the DTCs Sets

* The module suspends all message transmission.
* The MIL and battery indicators will illuminate, along with several DIC messages.
* The vehicle may continue to run for several minutes, then will stall and not start.

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, without a repeat of the malfunction.

Reference Information
Schematic Reference

* Data Communication Schematics Electrical Diagrams
* Control Module References Programming and Relearning

Connector End View Reference

Component Connector End Views Connector End Views By Name
Description and Operation

Data Link Communications Description and Operation Description and Operation
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

Verify that DTC U0074 is not set.

If the DTC is set, refer to DTC U0074 U0074