4/25721, 4/25771

Fault Code 4/25721, 4/25771





Malfunction indicated
Pedal potentiometer safety switch faulty

Fault symptom
Car goes into Limp Home mode. The TCS CTRL lamp lights up.

Test procedure

Note: Since the fault code can be activated accidentally if the accelerator and brake pedal are pressed simultaneously, begin by clearing the fault code and driving the car to see whether it is generated afresh. If it is, continue as described below.

1 Enter ISAT command code 207.
The ISAT display should show 8B007 with no pressure on the accelerator and 8B107 when the accelerator is pressed at least halfway down.
If an incorrect result is obtained with command code 207, continue with point 3.

2 Enter ISAT command code 27A to check that the SAT display shows accelerator travel as a percentage. For example:accelerator pressed halfway down = 80050.
If the above tests check out OK the wiring and throttle potentiometer are OK and the next step is therefore to fit a new pedal potentiometer.

3 With the ETS and ASR control units disconnected and the pedal potentiometer also disconnected, and with the ignition switched off, use a BOB to check the leads between the pedal potentiometer's cable connector and pins 2, 4, 14 and 17 of the ETS control unit for continuity or shorting to earth /+12 V.
Also, use a BOB to check continuity in the lead between pin 1 and socket 22 of the pedal potentiometer's unplugged connector.




4 With the ETS and ASR control units unplugged, the pedal potentiometer connected and the ignition switched off, use a BOB to check the resistance across sockets 14 and 22 also.
With no pressure on the accelerator, the resistance should be 13.1-16.2 kohms.
With the accelerator pressed at least halfway down, the resistance should be 400-500 ohms. If the resistance measured is OL, check fuse #15.
A useful tip is to switch between open throttle and idling by releasing the accelerator abruptly. If the resistance then remains at about 400-500 ohms, the pedal potentiometer is faulty and a new one should be fitted.
If the resistance measured is OL, check fuse #15.
In the event of other incorrect resistance measurements, change the pedal potentiometer.

5 If no other faults have been found with the above test procedure, clear the fault code and drive the car to see whether it is generated afresh. If it is, try fitting an ETS control unit that is known to be OK.