Diagnostic Procedures

Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK . After performing OBD system check, go to next step.
Turn ignition on, with engine off. Using scan tool, command 1-4 upshift light on and off. If light turns on and off as commanded, see DIAGNOSTIC AIDS . If light does not turn on or off when commanded, go to next step.
Turn ignition off. Disconnect PCM harness connector containing shift light control circuit. Turn ignition on. If shift light is off, go to next step. If shift light is on, go to step 5.
Connect a fused jumper wire between ground and shift light control circuit at PCM connector (harness side). If shift light is on, go to step 6. If shift light is not on, go to step 7.
Repair short to ground in shift light control circuit. After repairs, go to step 9.
Check connections at PCM. Repair as necessary. After repairs, go to step 9. If connections are okay, go to step 8.
Check for faulty shift light bulb, open ignition feed circuit to bulb, or shift light control circuit open or shorted to battery voltage. Repair as necessary. After repairs, go to step 9.
Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
Using scan tool, select DTC, CLEAR INFO function. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, then enter this DTC. Operate vehicle within conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2.
Using scan tool, select CAPTURE INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, go to applicable DTC test.