How to Fix EPC Light on VW Cars Polo MK4 9N

EPC Light on VW Polo MK4 9N

The EPC light problem happens while starting or even the EPC can turn on while driving.

The EPC light turns on and the car runs poorly. The fuel trim becomes rich. It smells like petrol behind the car. This is the limp home mode that allows you to drive the car home. At least like this you are not stranded.

If you stop the engine, the EPC warning light might go away or stay and after turning the ignition on in the car, the engine keeps revving up and down while in idle. The car cannot be driven at this point and it must be fixed.

These symptoms together with the EPC light and OBD2 scanner or VAG-COM / VCDS error codes related to the throttle body mean there is an error with the throttle body itself which can be expensive or with the electrical wiring near the throttle body.

At this point it’s a good idea to check the electrical connections on the throttle body. Steps shown in the video bellow.

EPC light fix on VW Polo 9N MK4

OBD2 Scanner Faults

Possible engine faults found with your OBD2 scanner.

17580 - Angle Sensor 2 for Throttle Actuator (G188) Signal too Low
        P1172 - 35-10 - - - Intermittent

17952 Throttle Actuation Potentiometer Signal too High
        P1544 - 35-10 this one is also Intermittent

Diagnose

They key here is that these problems are intermittent and also you might see ECU error codes that have the word implausable in their name. These errors or implausable errors mean something is very wrong with the car or a sensor is faulty. The fault of a sensor ca be caused by the sensor itself or by the electrical connection to the sensor.

VW EPC light problem RPM

The easiest to do is disconnect the throttle body connector and place it back in. This alone may fix the problem temporarily for a feww weeks or even months.

To fix this problem, you can try to clean the throttle body electrical conector and the wiring harness connector going in it with contact cleaner spray or WD-40.

I’ve noticed that when you use contact cleaner spray it works great but the problem will come back sooner. On the other hand if you use WD-40 to clean the contacts, the problem will not come back even after a few years. WD-40 keeps moisture away and makes the seal of the electrical connector work better.

Still not working

If you cleaned the contacts and still have the same problem, check the wires going into the electrical connector. Make sure no wire is broken or torn. If you see any damaged wires, you should repair them if you are able to or take the car to an electrician to fix it. A wire can be repaired by replacing the faulty wire or running another wire in parralel whru the harness and connecting the new wire instead of the old wire on the connector. The connectors have special contats so it may be difficult to replace the terminals.

It might be cheaper to replace the whole electrical connector going inthe throttle body.