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P1501 and P1503

Symptom: The "CHECK ACS" warning lamp is on. If no wheel speed is presented, the ACS control module calculates a default value on the basis of the gearbox input shaft rpm and the gear that is engaged. No other fault symptoms.

P1501 and P1503

P1501: Wheel speed, value wrong P1503: Wheel speed, signal wrong

Fault symptom

The "CHECK ACS" warning lamp is on. If no wheel speed is presented, the ACS control module calculates a default value on the basis of the gearbox input shaft rpm and the gear that is engaged. No other fault symptoms.

Condition

P1501: A gear is engaged and the clutch is in engagement.

No wheel speed.

Neither the brake pedal nor the accelerator is depressed

P1503: Wheel speed >250 km/h.

Important

A diagnostic trouble code for the wheel speed signal may be generated in connection with prolonged wheelspin on a slippery road, when running the engine with a gear engaged and the front of the car jacked up, or during brake testing on a roller device.


Check the wiring

Intermittent faults can occur as a result of temporary short circuits or open circuits. Jiggle the wiring harness at several points and in several directions to reveal loose connections in the wiring and connectors. Observe the multimeter, scan tool or test lamp while checking.

Diagnostic procedure

1 Check the ABS



Wheel speed is an input signal from the ABS control module. If the ABS lamp is on, check whether diagnostic trouble code B1381 or B1382 (wheel sensor LH rear, signal incorrect and no signal respectively) is present in the ABS system.

Is diagnostic trouble code B1381 or B1382 present?

yes

Continue fault diagnosis as described in "Brakes" .


no

Continue with point 2.


2 Check the wiring



- Unplug the Sensonic control module's 55-pin connector.

- Connect a test lamp to pins 37 and 31 of the female connector.

- Turn the ignition switch to the ON position.

- Spin the LH rear wheel.


The test lamp should flash.

Test lamp flashing?

yes

Continue with point 3.


no

Check the lead connected to pin 31 of the control module for continuity and shorting. Repair or replace it if necessary and then continue with point 3.


3 Final check



- Clear any diagnostic trouble codes.

- Perform a drive cycle by driving the car and checking that the speedometer and Scan tool diagnostics instrument show the car's current road speed.


Test results OK?

yes

The steps taken to rectify the fault were correct.


no

Continue as described in the section "Before replacing a control module", see .