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BMW Common ECU Failures Index Page

BMW 3 Series (1990-98). Both Bosch Motronic and Siemens engine management ECUs suffer water damage due to blocked heater fresh air inlet drain hose. This hose is triangular in shape and is intended to drain any water which collects in fresh air inlet. Leaves and other debris block this hose which allows water to build up eventually flooding ECU compartment and causing ECU failure. The fix is easy - shorten hose by 2cm at bottom with snips + clear drain pipe with thin wire as part of winter service. If your ECU has water staining, please click here for fast low-cost ECU inspection service.

MOST BMW models are fitted with Bosch Motronic engine management ECUs which suffer from common ignition failures. Bosch Motronic ECUs are also fitted to Alfa Romeo, Peugeot and Vauxhall (GM) cars from 1986 to date. TO PROCEED - It is important to count the number of ECU pins to correctly identify next page. Please click HERE for photos of these ECUs to assist identification. (Bosch identify their Motronic part numbers with prefix - 0261 20X XXX)

    For Bosch Motronic with 35 pin (2 rows) or 55 pin (3 rows) connector please click here to proceed.

    For Bosch Motronic with 88 pin (3 row) connector please click here to proceed.

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