Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Code 39 - Clutch Switch Error: Notes
Clutch switch is normally closed when the clutch pedal is at rest. When clutch is depressed, switch will change from off status to on status. ECM runs a diagnostic test that looks for a change of state in the switch logic. If there is a failure in the clutch switch circuit, a Code 39 will set and the SERVICE ENGINE SOON light will illuminate. Code 39 will set when engine temperature is greater than 194°F (90°C), vehicle speed is greater than 40 MPH and clutch switch test fails 4 consecutive times in one ignition cycle.
- When clutch is depressed, switch should go from closed to open and status on a scan tester display should change from off to on.
- This test will check for a poor ground to clutch switch.
- This test will determine if clutch switch is being supplied with battery voltage or if circuit is shorted to ground.
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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.