Volvo check engine light: How to fix common Volvo ECU problem.

Applies to many Volvo computers used on 240, 740, 760, 940 models. Water droplets drip onto the top of the ECU box and over time can get on the circuit board. Quite often this results in the car running rich, stalling, and throwing check engine light but water can create any number of problems.
Including but not limited to:
3517011 CU119X Bosch # 0280000554 554 5003707 CU119X Bosch # 0280000544  544
3517609 3517407 0280000561 561 5003926 5003953 3517370 9146220 0280000563 563
1367487 5003765 0280000541 541 5003954 9146222 B230F  0280000556 556 0280000933 933 5003952 3517368 9135138 0280000560 560 0280000939 939

How to fix:
◆ Remove the ECU by removing the kick panel on passenger side front. Remove the ECU cover by prying back the tabs that hold the cover to the ECU chassis.

◆ You will need good light to examine carefully the circuit board.




◆ If you find white tracks from minerals in water that leaked in likely electricity is leaking via these tracks. Carefully and thoroughly clean the circuit board with a Q-tip and WD40 or equivalent cleaner.



There are of course other causes that cause an ECU to fail but this is a common one, especially in places like the Pacific Northwest where we get a lot of rain.

Charles / EuroPartsHouse.com