Initial Inspection and Diagnostic Overview

CIRCUIT DESCRIPTION
The "Transmission Control Module (TCM) Diagnostic Circuit Check" is an organized approach to identifying a problem created by an electronic automatic transaxle control system malfunction. It must be the starting point for any transaxle electrical diagnosis because it directs the service technician to the next logical step in diagnosing the complaint. Understanding the chart and using it correctly will reduce diagnostic time and prevent the replacement of functioning components.

TEST DESCRIPTION
Number(s) below refer to circled number(s) on tile diagnostic chart.
1. Road tests vehicle and provides an opportunity to store a vehicle speed input DTC.
2. Checks to see if the TCM's self-diagnostic mode is operating and for any DTCs that may be stored in the TCM's memory.
3. Checks for proper transaxle hydraulic/mechanical operation with shift solenoids disconnected.
4. Checks for an open in the BLK/WHT wire.
5. Checks for power and ground to the TCM, opens between the ALDC and the TCM, opens between the transaxle diagnostic enable connector and the TCM, and for a faulty TCM.
6. Checks for a short to ground in the PNK wire.
7. Refers to Throttle Position (TP) sensor circuit test. (TP) sensor circuit test checks wiring and ECM for proper throttle position signal output to TCM.

DIAGNOSTIC AIDS
An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation. Inspect the TCM harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals and for poor terminal-to-wire connections. If throttle position (TP) sensor circuit test was performed and test results were normal, check further by disconnecting ECM connector C1 and reconnecting TCM connectors C1 and C2 and backprobing connector C2 with a digital multimeter. Measure voltage at connector C2 cavities 7, 8 and 9. If voltage is 9 volts or less at any cavity with the ignition switch in "ON," replace the TCM.