VW Golf – 2007
Customer reports Engine and EPC light are on, Car drives but had poor throttle response and sometimes no throttle control.
Customer reports car was jerking and local garage replaced coil pack – with the coil pack replaced the car wouldn’t rev up and was looked into further. They replaced the throttle body and the car now drove but wasn’t correct.
A full scan was carried out and the main faults were these:
- 17951 – Angle Sensor 1 for Throttle Actuator (G187) – P1543 – 000 – Signal too Small – MIL ON
- 17579 – Angle Sensor 2 for Throttle Actuator (G188) Implausible Signal – P1171 – 000 – – Intermittent
- + Various no communication faults with other ECUs (Guessing the ECU has been unplugged for testing)
With the airbox removed a quick inspection of the engine showed a 2nd hand throttle body had been fitted, the throttle body wiring had been repair (poorly)
First test was to check the supply feed and earth to throttle body – quick check with the multimeter showed a steady 5 volts. The next test was to measure the input and throttle feedback circuits, using a 4 channel scope –
- Channel 1 (Yellow) is 5 volt input voltage to throttle body
- Channel 2 (Blue) is sensor 1 on throttle body (reads 0-5 Volts)
- Channel 3 (Purple) is sensor 2 on throttle body (reads 5-0 Volts)
- As sensor 1+2 work backwards to each other the total off both sensors should equal the supply voltage – on idle sensor 1 is 0.6 Volts and sensor 2 is 4.4 Volts
- Point 1 – from idle quick press on the throttle
- Point 2 – as the throttle shuts sensor 1 stops reading any voltage
- Point 3 – 2 more presses on the throttle (Sensor 1 has stopped reading but sensor 2 is reading correctly)
With a phone call to the customer a new throttle body was ordered and fitted. Using VCDS the throttle body adaption was carried out and the car was started and tested. This time I used the graph function on VCDS to test the throttle body as this is what the ECU is seeing and would also test the repaired wiring
VCDS turns the voltage into a percentage but you can see the sensor 1 and 2 readings are now correct. We taped and secured the repair wires from the other garages repair.
This shows why trying to fix faults with 2nd hand parts is a lottery as the 2nd hand part they brought had the same fault as the original unit!