Shift Light: Testing and Inspection

1992 Chevrolet S10/T10 P/U 4WD V6-173 2.8LSECTION Testing and Inspection

Manual Transmission Shift Light Circuit Check:




Manual Transmission Shift Light Circuit:






Circuit Description:
The ECM uses information from the following inputs to control the shift light:

^ Coolant Temperature Sensor (CTS)

^ Throttle Position Sensor (TPS)

^ Vehicle Speed Sensor (VSS)

^ RPM

The ECM uses the measured rpm and the vehicle speed to calculate what gear the vehicle is in. It's this calculation that determines when the shift light should be turned "ON".

Test Description:
Numbers below refer to circled numbers on the diagnostic chart.

1. This should not turn "ON" the shift light. If the light is "ON", there is a short to ground in CKT 456 wiring, or a fault in the ECM.

2. This should turn "ON" the shift light

3. This checks for an open in the shift light circuit, or a faulty ECM.
RENDER: 1.0x

NO RELATED

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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.