184000624 - Z72 INTERFERENCE ERROR ON SPEED SENSORS

The diagnostic equipment signals the following error: "C1250 - interference error at speed sensors"
This error is signalled if the control unit detects that the speed of one of the wheels (transmitted by the sensor) differs by more than 6 km/h from that of the others. This happens if the magnetic wheel is not correct or is damaged, if there are impurities in the gap, or if the sensor fitting is not correct or the signal incorrect
Results of the tests
1CHECK USING DIAGNOSTIC EQUIPMENTAll OKProblems encounteredOperation
Connect the diagnostic equipment and, in the PARAMETERS ambient, display the wheel speed.With the vehicle raised on a two column lift, rotate the wheels by hand and check that the diagnostic equipment signals the change in wheel speed.Move on to Step 3One or more wheels do not signal the correct change in speedMove on to Step 2carrying out the checks on the wheel in question
2SENSOR CHECKAll OKProblems encounteredOperation
Visually inspect the state of the sensors involved (front and/or rear, right and/or left).

In particular, check:

  • that there are no metal shavings in the flywheel magentic tracks
  • that the sensor involved is correctly fitted
  • that the sensor involved shows no signs of abrasion or distortion
  • that there are no interference elements in the system wiring
  • after market components
Move on to Step 3Presence of metal shavingsClean the flywheel track
Sensor fitting faultyRefit correctly
Front sensor faultyReplace the sensor Op. 3340A30 RPM SENSOR (ONE) OF ONE L/H OR R/H FRONT WHEEL - R+R
Rear sensor faultyReplace the sensor    Op. 3340A34 RPM SENSOR (ONE) OF ONE L/H OR R/H REAR WHEEL - R+R
Magnetic wheel faultyReplace the magnetic wheel
3CHECK ON CORRECT OPERATIONAll OKProblems encounteredOperation
Delete the errors using the diagnostic equipment.Carry out three road tests in succession:    See Test 3340OA A.B.S. SYSTEM ACTUATION CHECK    See Test 3350AA ASR SYSTEM ACTUATION SYSTEM    See Test 3350EA ESP SYSTEM ACTUATION CHECKto ensure that the control unit checks whether there are any errors still present.Return to the workshop and check that the fault is no longer present using the diagnostic equipmentEnd of diagnosisThe fault persistsMove on to Step 1