Note. Before performing any diagnostic test, refer toWARNINGS, CAUTIONS and NOTES in DIAGNOSTIC TESTS .
Note. Testing individual components does not isolate shorts or opens. Perform all voltage tests using a Digital Volt-Ohmmeter Meter (DVOM) with a minimum 10-megohm input impedance, unless stated otherwise in test procedure. Use ohmmeter to isolate wiring harness shorts or opens.
Diagnostic Aids
Check for the following
- Open or short to ground between Transmission Control Module (TCM) signal and Engine Control Module (ECM).
- Short to battery between TCM and ECM.
- Message timeout from TCM.
- Faulty TCM.