Lambda light

[Laird Scooby]

You need to read the codes (or have them read) to find out why the MIL is coming on in the first place Derek.

Nobody can answer your question until we know what the codes are, it could be something easy and cheap or not.

[derek vivian]

Thanks Dave, It seems my Volvo specialist garage (DMW in Merton) would prefer to get the ECU tested so I will need to live with the light for the time being. It would be good to know if I could obtain a ECU as a replacement at whatever cost which might mean I do not have to be without my car for the time being. I would be pleased to hear from anyone who can offer a fully tested ECU. Derek

[Laird Scooby]

Therein lies the rub Derek - it sounds as if your garage want to test the ECU rather than testing what might be a simple fix and sell you a new ECU instead.
Alternatively they might offer you tuppence ha'penny and a brass farthing for your V90 on the grounds "the ECU has failed" when it might be something as simple as a Lambda sensor.

Speaking of which, when you reset the ECU by pulling fuse #1, from cold, how long does it take the MIL to come on?

[baggy798]

*the garage when someone enters with the check engine light on*

[baggy798]

It's probably an abs sensor related fault if coming on at speed.

[derek vivian]

Hi Dave, If I remove fuse no.1 for say 1 minute the light is immediately off when I restart the engine and comes on again after say 25 miles on M25. Does that tell you anything? Derek Vivian

[derek vivian]

Dave, I have just read again your post and you mentioned a Lambda Sensor. What is this and can one still buy them? Would it be worth doing this first before getting involved with a new ECU? Derek

[Laird Scooby]

Originally Posted by derek vivian

Hi Dave, If I remove fuse no.1 for say 1 minute the light is immediately off when I restart the engine and comes on again after say 25 miles on M25. Does that tell you anything? Derek Vivian

Sadly not. Is the engine cold before the restart? Also are you gong straight onto the M25 or do you have a few miles to drive before reaching it? Is it normal M25 nose-to-tail rush hour traffic or is it free-flowing (rare i know!) at normal motorway speeds?
If you stop with the engine hot after the light has come on and pull fuse #1 and replace, if you drive off straight away how long is it before the MIL comes back on?

Originally Posted by derek vivian

Dave, I have just read again your post and you mentioned a Lambda Sensor. What is this and can one still buy them? Would it be worth doing this first before getting involved with a new ECU? Derek

In Laymans terms, the Lambda sensor measures exhaust gas oxygen content (sometimes also called an Oxygen sensor) and tells the ECU what the mixture is doing and the ECU then adjusts accordingly. If there is no output for a predetermined time from the Lambda, the ECU decides the sensor is dead and puts the MIL on.

They're relatively simple to change but you will need the correct socket for it and ideally a 2' breaker bar to drive it as they become fairly stuck.

https://www.ebay.co.uk/itm/121797379586

That will do the job, the Lambda sensor is in the exhaust downpipe, possibly as far down as the cat. Usually has 3 wires coming from it into a plug. Sometimes 4 wires are used and it looks like yours is 4 wires :

https://www.ebay.co.uk/itm/154851929368

That should be the corect sensor for your car, if you are on the original sensor and it's done over 100k miles (it's certainly over 10 years old!) it would be wise to change the Lambda sensor anyway - it might be the cause of the problem but no guarantee until you've fitted it and pulled fuse #1 and driven it a while.

[derek vivian]

Thanks Dave and I have ordered the second one you gave ebay details ending 368. When I receive it I will take it to DMW to arrange fitting. They are expecting me as and when! Derek

[Forrest]

Before you start throwing parts at this problem has anyone actually read the codes?

Referring back to my advice in post #3, a 1997 V90 should be ISO9141 OBDII. This means that even the cheapest, sub £20 code reader should be able to make a decent stab at reading an ECU error code.

If it is a P0422 Catalyst efficiency below threshold error, then my experience since September last year might also help. I must admit that I had bought a new Bosch rear sensor but had not got around to fitting it. My MOT came due in December and I was told I needed a new front pipe / catalyst. Non-OEM was not especially expensive. The garage refitted the existing sensors and I have not had the lambda light come on again since. I have now stopped carrying my Foxwell scanner to reset it.

Sometimes its just a case of going straight for the root cause!