Intermittent Engine Management Light

[onthecut]

Hi Guys.

Not long after I got the current ride it developed a fault where the engine management lamp would come on upon re-starting the car. First start of the day -- no lamp. If you then did a journey of any length without turning off -- no lamp. If however you stopped after just a very short stretch and re-started, the lamp would come on and on every subsequent occasion until the car was left overnight. In the end it decided to stay on permanently.

Having an identical spare car, which didn't do this, I set about changing, one at a time all the visible sensors (although I now realise, not the crank sensor) which made no odds. I finally swapped the ECU -- hey presto -- lamp out. You can guess the next bit --- the lamp has started coming on again, just as before. I can't be absolutely certain but I reckon it does knock the performance down when it's on -- although not the economy. We're not talking limp home mode by any means, but more leisurely acceleration over 70. I'm inclined to think the present one doesn't have quite the grunt of one or two of the others I've had, but on the other hand it doesn't do black smoke, either, which is nice.

All thoughts welcome.

Mike.

[xmexclusive]

Hi Mike

The primary function of an ECU is to run its specific part of the car. The standard ECU secondary routines are to identify and record those sensor and system malfunctions that it is capable of seeing for future fault finding analysis. Many ECU's also have a further series of capabilities programmed into them to respond to a specified number of sensor faults or a combination of sensor faults by using warning lights and perhaps running that system or engine with modified/reduced parameters. When the car is restarted the ECU's go through a reset routine but that does not clear ALL the prerecorded faults just those the system designer deemed non-critical. It effectively can turn the clock back but not all the way so the warnings will reappear after a smaller number of new sensor faults. This is why it is important to get ECU's reset after rectifying faults. I suspect that when you put the replacement ECU on the car the original faulty sensor or engine set-up item was not rectified and a clear or relatively clear ECU has now picked up enough permanently recorded faults to behave exactly as the original ECU did.

My most recent aquisition has started flashing the engine management light every half mile and cuts power if I try to rev beyond 4000rpm. It also idles a bit variably typically on the high side. My suspicions are heading towards the injector with the sensor playing up but I will get the faults read as soon as I can.

I really need to get a ELIT to be able to read faults properly but there is no way I will pay the current ebay asking price of £500 for secondhand kit. One of the local Citroen dealers has just gone to the wall so I am waiting for the receivers auction hoping the ELIT has not gone walkies.

John

This post has been edited by xmexclusive on January 25, 2009 12:08 pm

[onthecut]

Hi John.

That makes a lot of sense. I might give a local indie a try for code reading -- it's rumoured he has the relevant kit and it's about £20 a plug-in, which would be worth it for an accurate diagnosis.

Mike.

[xmexclusive]

Hi Mike

My problem this end is in getting someone with a code reader that will let me see what they are doing and have a record of the results found. Being charged for being told verbally that it is component X or even worse charged for no fault found is the bit that irks me. Hence the wish to become independant.

John

[techmanagain]

My problem this end is in getting someone with a code reader that will let me see what they are doing and have a record of the results found. Being charged for being told verbally that it is component X or even worse charged for no fault found is the bit that irks me. Hence the wish to become independant. (Quote)

If it is being diagnostic-tested by a Citroen Agane. he will produce a printed report at the end of the test. Then he is supposed to quote you for the repair of that fault. Most of the reasonable one do not insist on this and will give you a copy of th report - it's no use to them if you refuse to take up their offer at this point. Sweet reason may let them produce it for you in return for the necessary test fee being offered. (If I remember correctly, that is about 33% of the dealership hourly rate laid down by Citroen)

[steelcityuk]

Hi Mike,

If you're near Sheffield or passing and want them reading with a Lexia let me know.

Have you tried reading the blink codes?

Steve.