Fault: Codes B1012 and B1020 on reading the CIM of an Opel Vectra C

The vehicle displays two specific fault codes in the control unit integrated into the steering column:

B1012 – Steering wheel angle sensor not calibrated.

B1020 – Steering wheel angle sensor. Functioning or limit value problem.

The fault indicator light for the stability control system (ESP) is on on the instrument panel when driving the vehicle.

The warning indicator light for the electro-hydraulic steering system (EHPS) is on on the instrument panel.



The indicator light stalk may malfunction, it does not return to its initial position.


 The cause of this fault is nothing more than a internal failure of the steering angle sensor (SAS), which is located inside the control unit (CIM) integrated in the electro-hydraulic power steering column (EHPS system). Unfortunately, due to the soldering of the sensor in the unit, it is not possible to repair it separately to reduce the cost of the fault repair, the complete module (CIM) must be replaced with an up-to-date version.


The repair procedure is as follows:
1 – Take a reading of the fault codes recorded in the electro-hydraulic power steering control unit (CIM) and check that described codes B1012 and B1020 are recorded.
2 – Check that the fault indicator light for the stability control system (ESP) is on when driving the vehicle on the road.
3 – Check the correct operation of the indicator light stalk.
4 – Check that there are no short-circuits or defects in the steering control unit wiring.

5 – Carry out a basic adjustment of the steering stops.
6 – Check the parameters of the steering angle sensor with the diagnostic tool and confirm that the stop values are between -500° and 500°.
7 – If confirmed that the fault comes from the steering angle sensor, the steering control unit (CIM) must be replaced with a modified version with updated software for this unit.
To ensure the control unit (CIM) is being replaced with an updated version, as the part reference is still the same, check that it has a blue circular adhesive label and the manufacturing date is later than 020501 (1 May 2002), manufactured by DELPHI.