Powertrain Diagnostic Procedures: Introduction: Notes

IMPORTANT: New for TJ, the Powertrain Control Module and Transmission Control Module have been combined into single control module on all vehicles equipped with a 2.4L and 4.0L engines. This new module is the Next Generation Controller (NGC). New Diagnostics procedures along with new DTC's are two of the changes you will see which reflect the new combined module technology. The NGC modules will have four color coded connectors C1/A through C4/D, (C1-BLK, C2-ORANGE, C3-WHITE, C4-GREEN). Each PCM connector has 38 pins. Two new tools were introduced to help diagnose and repair the new PCM (NGC) terminals and harness connectors. The Miller #3638 terminal removal pick must be used to release the connector terminals, or harness and connector damage will occur. Also, the Miller #8815 Pin Out Box was introduced. You must use the Miller #8815 tool instead of probing the PCM terminals, or harness and connector damage will occur. There is also a new Verification test and module replacement procedure for the new PCM.

The procedures contained in this article include specifications, instructions, and graphics needed to diagnose the PCM Powertrain System . The diagnostics in this article are based on the failure condition or symptom being present at the time of diagnosis . Please follow the recommendations below when choosing your diagnostic path.

First make sure the DRBIII® is communicating with the appropriate modules; i.e., if the DRBIII® displays a "No Response" condition, you must diagnose this first before proceeding.
Read DTCs (diagnostic trouble codes) with the DRBIII®.
If no DTCs are present, identify the customer complaint.
Once the DTC or customer complaint is identified, locate the matching test in the Table of Contents and begin to diagnose the symptom.

All component location views are in COMPONENT LOCATIONS . All connector pinouts are in CONNECTOR PINOUTS . All system schematic diagrams are in SCHEMATIC DIAGRAMS . All charts and graphs are in CHARTS AND GRAPHS .

An * placed before the symptom description indicates a customer complaint.

When repairs are required, refer to the appropriate service information for the proper removal and repair procedure.

Diagnostic procedures change every year. New diagnostic systems may be added; current systems may be enhanced. READ THIS ARTICLE BEFORE TRYING TO DIAGNOSE A VEHICLE DTC. It is recommended that you review the entire article to become familiar with all new and enhanced diagnostic procedures.