BMW Common ECU Failures


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All late petrol HP BMW models (2007 onwards) can suffer impossible to diagnose, combustion misfire, NOX, bank 1 +2 cat faultcodes.  Logged after warm up phase has been completed.  Mostly after replacing a coded petrol injector.  Reason being the faulty injector current draw can damage the logic chip.  Beware fitting pattern injectors.

Most 2005 onwards 5 series suffer battery issues due to supply lead corrosion at the point it passes through the boot load space floor.

All BMW models after 09/1998 can suffer can suffer non starting with engine cranking do to immobilizer control module software problems, only cure is to fit later module part number 61354101593 with higher version software, above 2005.

3 series (E46) new shape light control module.  A lot of new BMW 3 series are suffering from headlight failure due to the car's light control module. We have noticed this ourselves as it is usually the right head headlight that is out.  Due to the cost of these modules, its worth having them tested/repaired.
3 series (E46) 2000-03 heated oxygen sensor and ECM faultcodes with no loss of engine performance on E46 models from 2000-03 can be attributed to a software programming fault.

3 series (E36) 1994-99 engine type 206S3 suffer problems with 206S3 ECU  pin 48 crankshaft position sensor output less than 5khz output with ignition on, due to a possible random ECU internal fault.  Stalling after hot or cold starts, faultcode 41 problem MAF sensor is more likely to be dirt in idle speed control valve, replacing MAF sensor to solve trouble code 41 will not work!

7 series (E38) 1994-99 730i suffer problems with ECU pin 40 heated oxygen sensor output, due to a possible random ECU internal fault.

X series (E 53) up to 08-2000 fitted with M54B30.  When turning the steering wheel at idle the X53.OI vehicles equipped with M54 engine may hesitate and stumble. No fault codes are stored in the DME.  Problem is with DME/ECM calibration.  Reprogramming of the DME with updated software is the only cure.

5-7 series Siemens PDC parking distance control unit mounted in spare wheel well, silly no stupid place to put it.  These modules are can-bus connected via two core soft twisted wire.  Should the module be corrupted with water, which is a common fault.  Later replacement modules will need to be reprogrammed!  It is rumoured thru the trade, the Siemens software supplied to the maindealers.  Has glitches & is prone to crashing.  As it requires complete programming of all multiplexed units on the car, not just programming the replacement PDC unit.  Should the software crash without establishing protocol thru all the multiplexing modules in the car.  You could well be in a position of a non start car, needing replacement of many or all of the expensive can-bus modules, including the main engine ECU.  If the PDC fails, live without it.  You could drive your car into the main dealer & have to tow it away, never to run again.  We have heard of two instances of this.  If you are thinking about attempting a PDC repair.  Ring me & I will do my best to put you off the idea...  Reason being I cannot stand the embarrassment of vehicles being driving into our workshop and subsequently being towed away.

BMW early EDC diesel pump EDC Pump actuator performs on test but on vehicle you get idle surge or stalling problems.  It is caused by wear in the actuator bushes.  Fault manifests itself as a temperature related fault.  Worn actuators are difficult to diagnose in situ.  Six cylinder engine is a powerful motor in the BMW 325/525 and Vauxhall Omega but struggled a bit when fitted into a RangeRover.  Bosch VP37 pump is on the whole very reliable

BMW common rail diesel injectors fitted to later model diesels fail wholesale and cost the earth.  Best avoided.

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.

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 all suffer intermittent internal power up faults.

Any early BMW which has had the service light extinguished by grounding to earth, pin 7 in the 30 pin diagnostic plug, must be treated as having a suspect ECU module.  Problems include having the ABS light on any BMW up to year 2000 but no code stored, plus problems obtaining faultcode read thru pin 20 in diagnostic plug.  ECU likely to be corrupted by having the service light extinguished by putting an incorrect current load on pin 7.  Someone may have thought they were saving money by not buying the correct service tool.

Early E36 with airbag warning light in steering wheel this is a retrofit complete unit, so there is no connection to the diagnostic socket and no diagnosable parts in this system. That is why you cannot communicate using any diagnostic tool.

Early BMW models including 1982 633CSI/733I.  1983 533I/633CSI/733I.  1984 533I/633CSI/733I suffer hesitation /poor throttle response in first 5 to 10 min of operating after Starting with a cold/warm engine at an ambient temperature above 23 deg Celsius.  The cause being a new generation Montronic Control Unit fitted was not sufficiently re-programmed to compensate for the removal of the external 560 ohm resistor. The solution to this fault is the installation of an external resistor in the NTC line.

ECM modules.  It is important to count the number of ECU pins to correctly identify.  (Bosch identify their Motronic part numbers with prefix - 0261 20X XXX)Bosch Motronic with 35 pin (2 rows) or 55 pin (3 rows) connector.  Bosch Motronic with 88 pin (3 row) connector.  Most failures are with the 55pin ones, which are believed to be made in Eastern Europe.

DIS coil per cylinder system (Alfa + BMW) All suffer mechanical damage on occasions, thru rough handling when servicing plugs.  Worth checking before looking at ECU due to ignition faults.

E61 Estate 2007  (see photos below)  Who would fit two can-bus control modules in the spare wheel well?  Answer BMW would!  Self leveling air suspension stuck at maximum. 


Page updated 28-05-18