Volvo ECU Common Problems

Volvo ECU Common Problems

Page updated 28-05-18

Volvo XC90 P2 platform vehicles 2002 - 2014 suffer front window wiper failure. This is due to corrosion thru loom to BCM pinouts. The normal cure for this, is new loom and a new BCM module. Supply has run out for some early 2004 BCM units now (even at any cost). If you present the vehicle to our workshop we can enact a hard wired repair from the loom directly to the BCM PCB.

Volvo XC90 P2 platform vehicles 2002 - 2014 suffer ABS pump failure (drop relay faults). This can sometimes be mis-diagnosed. Hidden loom failures are very common (not a nice job to find).

S60-S80-V70-V70XC-XC70 2001 onwards suffer output problems from main ECU to variable valve timing solenoid, faultcodes 640A 641A 643A 644A 640F 641F stored.

Radio codes. Volvo UK are the only manufacturer that will supply radio codes generated from vehicle VIN numbers free of charge. They will need a copy of the VL5. Registration document to confirm ownership. If your local main dealer will not supply the code, ask them for the Volvo UK 0845 number (this number changes from month to month). Fax or email them a copy of your VL5, or they will not supply. Other manufacturers charge £15 plus for radio codes. Peugeot being the most expensive at £30 plus. But most radio codes can be obtained via eBay at very low cost, £5ish (18-03-07).

VOLVO 440-480 multi-function unit problems This unit positioned in the passenger foot-well suffer from intermittent failure due to water ingress from leaking windscreen seals. It is a very common failure on ES coupes, due to the body shape and subsequent water ingress.

Volvo V70 generation 2 suffer electric window problems due to failed diodes in the drivers side door control panel.

Volvo V70 all models suffer major harness and fusebox shorts relating to the immobilizer key reader circuit.

VOLVO 850 ABS PROBLEMS The ABS ECU fitted to Volvo 850 (with or without traction control) is now causing problems with vehicles failing annual or roadside safety tests because of ABS failure. ABS warning light REMAINS ON after switching on ignition - most usually there is a history of the ABS light operating intermittently for some time. This means the ABS system has switched off and the automatic antilock function is NOT operating although the brakes remain effective.

ALL VOLVO FUEL INJECTION MODELS up top 1994 - Intermittent poor/non start. Has vehicle got a radio suppression relay? (white color near front fender) If yes REPLACE! (radio suppression relay supplies injector 12volts - any problems here can cause injector mis-operation)

VOLVO 740/760 TURBO MODELS with Bosch Motronic engine management ECU and LUXOR injection amplifier 1986-90. Motronic ECU part numbers 0261 200 022 and 026. Motronic ECU is located inside car - LUXOR is black painted cast alloy box mounted vertically immediately behind battery with large connector on top edge.
VEHICLE OCCASIONALLY BREAKS DOWN ON ROAD OR FAILS TO START (but sometimes starts after waiting). Breakdown services (repeatedly) diagnose engine management ECU (Bosch Motronic) failure.
1. Problem is more likely to be LUXOR injection amplifier ECU which is part of traction control system - standard fit to these cars whether traction control specified or not. Luxor ECU is black painted cast alloy box mounted vertically immediately behind battery with connector on top. Luxor ECU takes 5V level output signal from Motronic and amplifies this to drive injectors. WITH TRACTION CONTROL FITTED - If the ABS system detects drive wheel speed differential (brakes NOT applied), this ECU will switch off first 1 injector, then 3 injectors (if wheel speeds still different)
2. Liberally spray Luxor connector and pins with WD40 and road test before proceeding.
3. Diagnosis takes some time and involves using oscilloscope to monitor input (Luxor pin 16) pulse signal from Motronic and output pulse to each injector (Luxor pins 17/18/19/20). Failure is indicated by reduced amplitude of output injector pulse (which can be momentary and intermittent) - banging Luxor can help speed things up!
4. Sending Luxor ECU for reconditioning anyway may be best option!

VOLVO (CAT and NON CAT) 240/440/480/740/745/760/940 MODELS with Bosch Jetronic LH 2.2 and 2.4 fuel injection ECUs 1988 onwards. ECU part numbers 0280 000 5XX/56X/590/591/594/595/935/others.
VEHICLE BREAKS DOWN ON ROAD OR FAILS TO START FOLLOWING SHORT JOURNEY. Breakdown services diagnose Bosch Jetronic LH fuel injection ECU failure - loss of fuel pump relay control from ECU pin 20.
1. Identify fuel pump relay and remove. Connect jumper lead to provide 12 volt feed to fuel pump, after identifying relay socket pins.
2. If car now starts and runs, take for road test. (put on exhaust gas analyser first with catalyst equipped vehicles). IT IS NOT OK to use car with fixed feed to fuel pump.
3. If car now runs ok, ECU confirmed failed.
4. If car doesn't run with jumper lead fitted, there may be other causes of breakdown.

VOLVO (CAT and NON CAT) 440/460/480/ MODELS fitted with FENIX (35 pin) (RENIX on Renault) engine management ECUs 1989 onwards.
Vehicle suffers from poor idle speed control following work in engine compartment - especially tune up. Possible un-repairable damage to ECU idle control circuits due to crossing over idle control valve and throttle position switch connectors. These connectors can be undone whilst setting base idle speed or mixture.
This problem is most likely to occur on vehicles (both Volvo and Renault) with 1.7 litre engines. On some cars these connectors are identical un-keyed 3 way connectors. The effect of crossing over is to apply earth directly to idle control IC within ECU - It is destroyed immediately ignition is turned on. This part is not commercially available so ECU cannot be repaired apart from robbing another ECU.

1. Confirm vehicle has 35 pin FENIX/RENIX system (BENDIX or SIEMENS stamped clearly on cast alloy ECU cover).
2. Confirm vehicle has idle control valve and throttle position switch with identical 3 way connectors in wiring to each component.
3. Confirm wire colors match each side of connectors.
4. If wire colors don't match, open ECU and look for obvious internal damage.
5. Even if wire colors match, open ECU and look for obvious internal damage (connectors could have been changed back).

(12-03-11)