Case Study - E38
ABS, DSC and Brake Warning Lights Illuminated

Date of manufacture	Oct 2000
Mileage	110,000
Model	740i
Engine	Vanos M62

Symptoms

The E38's produced after 10/1998 can suffer from ABS failure that bungs up fault lights for ABS, DSC and Brake Warning, the lights are all orange (warning) rather than red (failure). The fault is often intermittent, sometimes the fault only appears when the engine is hot. On other cars the lights only illuminate when the car is driven over 30 MPH (or lower under harsh acceleration). Carsoft will show a failure of one of the rear speed sensors, replacing the sensor will make no difference. The speed-sensitive failure may show 'Error 92 pressure sensor (pre charging pump).

The cause

This heat-sensitive failure is due to the intermittent failure of the Bosche control unit that is strapped to the ABS pump. It is quite often the heat from the engine that permeates the control unit which causes the failure. The speed-sensitive failure is due to the failure of the pre-charge pump.

The fix

The repair is covered here.