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.

Checking power supplies

We are going to do a bit of revision, and what better than an everyday example:

A vehicle comes into our workshop that does not start or does so with difficulty.

We verify that it does not start, and then the first thing we do is check the existing or stored errors using the diagnostic apparatus.

 On the diagnostic machine we see that there is an injection relay error. Next, and due to the ease of testing another relay, we replace this relay to see if it is indeed malfunctioning (this is a common 20 amp relay, and there are bound to be some in the workshop), we fit the new relay and test it.
The car continues to have the fault and does not start, there is no other option but to start checking the installation.

Evolution of exhaust systems between 1990 and 2014. Euro standard

Exhaust system technology has evolved continuously as a result of European environmental requirements. The purpose of all of these requirements is to control the levels of polluting gas emissions and noise from all vehicles sold in the European Union. The way in which vehicles are checked for compliance with the standards after sale is to check them at vehicle technical inspection centres (ITV/MOT). The controls required of the manufacturers have obliged them to create new exhaust systems to reduce the amount of polluting gas emissions to the atmosphere.

Evolution table of the EURO standards for control of exhaust gas emissions.