Mercedes-Benz W124 throttle body wiring harness
The W124 M104 responds poorly to the throttle – could the cause be the throttle body wiring harness?
Yes. The wires to the throttle motor and the magnetic clutch crack and become brittle along their whole length from the connector to the throttle. After they were renewed, the car responded better to the throttle and also pulled well at part throttle.
How is the throttle wiring harness repaired?
Replace the wires one at a time, so the risk of mixing them up is small; silicone wire works well. The wires should be renewed all the way from the circuit board, because the rest of the harness is often just as brittle. The connector can be removed completely if it cannot be opened. Clean and grease the throttle mechanism at the same time.
How do you recognise a wiring fault?
The wires have cracks, oxidation or breaks, and the problems get worse the further you go from the connector. Inspect the wires visually between the throttle body and the connector.