As I’ve been recovering from surgery, I’ve not been using my car, so to preserve the battery (now around 9 years old), I connected (well actually, my other half connected) my excellent CTEK battery charger, at first using the croc clips, then, when I was able to, using the comfort connector- a socket that is connected to the car permanently.

Doing this upset things: when I went to try and start the car, I got a load of warning lights, and plugging in the diagnostics revealed a fault code for the steering angle sensor:


00778 - Steering Angle Sensor (G85)


Clearly dicking about with the battery terminals had lost the basic setting.

The sensor simply tells the ECU how far the steering wheel has been turned, and is needed, and calibrated, so that the Stability Control knows which way the wheels are pointing, and also so the Steering Assist ECU can adjust the steering weighting according to speed and how much steering lock is applied. As such, you have to tell the Stability Control (part of the ABS controller) where straight ahead is, with this procedure, and then allow the car to calibrate where the two ends of travel of the steering rack are by following this procedure, which is why it’s remained undone until now, now I’m able to drive short distances and manage the steering with little power assistance.

In the event, it took several attempts at the second procedure, which is why today found me sitting in an quiet industrial estate, with the car running and a laptop on the passenger seat, and even then, it took a short drive and several lock-to-lock moves to clear. The steering was both very heavy and devoid of feel until all of a sudden, the fault lamp cleared, the steering got lighter, all started working correctly, and a scan produced this:

All a bit complicated, really, but that’s the price we pay for all the fancy active safety gear, and another sign of how car systems interact: the steering angle sensor will report an error in the steering assist ECU, but the basic settings are set in the ABS/Stability controller, and both controllers get upset if this setting is lost.