I have a Volvo V40 1.8 which very recently has been indicating an ECU warning light which doesnt go out after restarting the engine or leaving the car overnight....it does go out later at some apparently random interval. Details below...sorry if it is a little long winded.
If any experts have any ideas I would be grateful, the car is booked in for a diagnostics check next week and it would be great to have some ideas before the service manager tries to blind me with technical jargon.
Many thanks
Ian
Volvo V40 1.8XS 2000MY ECU warning light
Apart from engine stuttering when ECU light turns on no other symptoms.
1. 19/6/02
Driving in slow moving /stop-start city traffic for 10 min, engine stuttered then recovered but with ECU warning light on. (dont know if fan had started). Stopped and restarted engine at traffic lights but light still illuminated when engine running. Parked car for approx 3 hours. On restarting the car the light extinguished as normal once engine running.
Warm sunny day.
2. 29/6/02
10 miles of slow moving traffic on M5, engine coughed then recovered, fan started and ECU light illuminated. ECU light stayed on for next 80 miles. Stopped car at destination. Restarted car several hours later in the evening and ECU light still on when engine running, stopped engine after test.
Left car overnight and in the morning the ECU light went out normally once engine was running
Warm sunny day
3. 1/7/02
15 miles of slow country lanes at under 30mph, 2nd and 3rd gear. Towards end of journey engine stuttered, fan started and ECU light came on. ECU light remained on when car restarted that evening. ECU light still on when engine running the next morning. After a 7 mile drive the car was left parked for 4 hours. On restarting the engine ECU light turned off as normal once engine running.
Cool damp day
4. 5/7/02
After a 20 mile dual carriage way trip at 60mph drove on slow country lanes after a few miles engine stuttered and fan and ECU light came on. Continued to destination (few miles) and parked car. ECU light still on next morning when engine running, remained on for 40 miles until a 2 minute stop at motorway services when engine was turned off, light extinguished when
engine restarted.
No further problems to date.
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Ian,
Lambda Sensor is certainly a strong possibility, but there are loads of others as well !! Had a similar problem with my own 2.0Turbo V40 last year (still under warranty). Fault code indicated a Crank Angle Sensor fault - dealer changed the sensor, the sensor mountin/shield, and eventually the flex plate between the gearbox and engine which carries the CAS. In my case the only actual problem was difficult starting - once started the light was on but engine ran 100% OK.
The first thing to do is see what fault codes are stored, so you have to wait and see what they come back to you with.
Best of luck, Adam
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Update
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Car in today (first free time at Volvo garage) will keep
everyone posted.
Under normal circumstances this car does no journeys shorter than
10 miles, no commuting, the problem only occurred on holiday when I got stuck in roadworks or was driving around narrow country lanes (narrow with passing places and very tall hedges to limit visability).
Presumeably if I were to use this car to commute into Oxford every day I would see the warning light almost continuously?
Surely a modern car can cope with this type of use. If the fuel mixture is too rich then something must be wrong with the ECU
which controls it....but I get almost 40mpg on normal driving
so it cant be that far out.
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Garage just rang. The fault code was for the MAF sensor, which is now all within tolerances and ok, they have reset the ECU and checked everything and want to try it again, nothing replaced.
So exactly what do all of these sensors actually do/measure?
eg MAF, Lamba, etc. I guess the crank sensor simply tells the ECI when the engine is at TDC for each piston.
Good that the code was readable almost 3 weeks after the first occurence and over a week since the last. At least it is not just my word about a fault that has now apparently cleared up.
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Ian,
Mass Airflow Meter (MAF) measures volume of air entering inlet manifold. Lambda (or Oxygen) Sensor monitors Oxygen level in raw exhaust product (ie ahead of Cat) to enable fine trimming of air/fuel ratio. Crank Angle Sensor (CAS) measues engine rpm, but may also identify No.1 cylinder. Some engines also have a Camshaft Sensor for cylinder identification. In addition you have Coolant Temp Sensor, Throttle Position Sensor, Air Temp Sensor and so on, all values contributing to the Electronic Control Module (ECM) mapping of igniton timing and fueling.
HTH, Adam
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