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

		Test results
1	CHECK USING DIAGNOSTIC EQUIPMENT	All OK	Problems encountered	Operation
	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.	Go to Step 2	One or more wheels do not signal the correct change in speed	Go to Step 2 carrying out the checks on the wheel in question.
2	SENSOR CHECK	All OK	Problems encountered	Operation
	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 magnetic tracks - that the sensor involved is correctly fitted - that the sensor involved shows no signs of abrasion or distortion Check that there are no interference elements in the system wiring: - Electromagnetic wave sources	Go to Step 3	1. Presence of metal shavings 2. Sensor fitting faulty 3. Left front sensor faulty 4. Right front sensor faulty 5. Left rear sensor faulty 6. Right rear sensor faulty 7. Presence of electromagnetic wave sources	1. Clean the flywheel track 2. Refit correctly 3. Replace the sensor Op. 3340A30 RPM SENSOR (ONE) FOR ONE FRONT WHEEL, LEFT OR RIGHT - R.R. 4. Replace the sensor Op. 3340A30 RPM SENSOR (ONE) FOR ONE FRONT WHEEL, LEFT OR RIGHT - R.R. 5. Replace the sensor Op. 3340A30 RPM SENSOR (ONE) FOR ONE FRONT WHEEL, LEFT OR RIGHT - R.R. 6. Replace the sensor Op. 3340A30 RPM SENSOR (ONE) FOR ONE FRONT WHEEL, LEFT OR RIGHT - R.R. 7. Eliminate the sources of electromagnetic waves.
3	CORRECT OPERATION CHECK	All OK	Problems encountered	Operation
	Delete the errors using the diagnostic equipment. Road test the vehicle See Test 3340OA ABS SYSTEM INTERVENTION CHECK See Test 3350AA ASR SYSTEM INTERVENTION CHECK See Test 3350EA ESP SYSTEM INTERVENTION CHECK to 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 equipment	End of diagnosis	The fault persists	Go to Step 1