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.
1989 Mercedes Benz 300CEFACTORY OEM SERVICE PROCEDURE
Throttle Position Sensor
- Disconnect 3-pin TPS connector located near fuel pressure regulator. With throttle closed, connect an ohmmeter between Black wire and Brown wire. Ohmmeter should indicate continuity.
- Open throttle to wide open throttle. Ohmmeter should indicate infinity. Connect ohmmeter between Brown wire and Green wire. With throttle closed, ohmmeter should indicate infinity.
- Partially open throttle. Ohmmeter should indicate infinity. Open throttle to wide open throttle. Ohmmeter should indicate continuity. If ohmmeter does not read properly, loosen TPS adjustment screws. Adjust TPS to obtain proper ohmmeter readings.
Factory Service Tools
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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.