These tests assume a shift light problem exists. Use this procedure only if the light will not illuminate, or illuminates all of the time.
Turn ignition on, with engine off. Note shift light. Shift light should not be on. If light is on, check for a short to ground between the bulb and the ECM, or a bad ECM. See Fig 1 .
With ignition on and engine off, ground test terminal of ALDL connector. SERVICE ENGINE SOON light should start to flash and shift light should come on. If light comes on, go to next step. If SERVICE ENGINE SOON light does not flash, perform DIAGNOSTIC CIRCUIT CHECK in BASIC TESTING article in this section.
If shift light does not come on, ground Tan/Black wire at appropriate ECM terminal using a jumper wire. See SHIFT LIGHT CIRCUIT IDENTIFICATION . If light still does not come on, check for blown GAUGES fuse (AIRBAG fuse on Corvette), blown bulb or open circuit between fuse and ECM. If light comes on when grounding terminal with a jumper wire, problem is a bad ECM connection or bad ECM.

SHIFT LIGHT CIRCUIT IDENTIFICATION

Application	ECM Terminal
Seville	B7F

Fig 1: Shift Light Schematic

Courtesy of GENERAL MOTORS CORP.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

Shift Light