Tony

[boaty]

I have a 940LPT ex Demonstration model bought in 1996, the Lambda light is now lit , the engine cut out momentarily and now it runs perfectly with the lambda light on. My mileage is approx. 109,000. Do I need to replace the lambda sensor and please can you tell me where is it ? Also who is the best source of sensors if it needs replacing?

[Laird Scooby]

Originally Posted by boaty

I have a 940LPT ex Demonstration model bought in 1996, the Lambda light is now lit , the engine cut out momentarily and now it runs perfectly with the lambda light on. My mileage is approx. 109,000. Do I need to replace the lambda sensor and please can you tell me where is it ? Also who is the best source of sensors if it needs replacing?

First, read the codes. It could be the Lambda sensor but the light is an Engine Management Light so could be any number of faults.

Secondly, remove fuse #1 for a couple of minutes to clear the codes and replace. Take it for a test run and see if the light comes back on. If so, read the codes again.

Given the mileage and age of the car, the Lambda sensor is likely to be dead or nearly so could be a wise move renewing it. If/when you do, pull fuse #1 for a minute or two afterwards to clear the old fuel trims and any fault codes.

[boaty]

Thank you Dave that gives me soma ideas to go on
Is the sensor in the engine bay or underneath ?

[Laird Scooby]

Originally Posted by boaty

Thank you Dave that gives me soma ideas to go on
Is the sensor in the engine bay or underneath ?

Yes!

Depends on the year it was made, what exhaust system was fitted to it and a few other things. Some Lambda sensors were mounted in the engine end of the cat, others further up towards the exhaust manifold.

I strongly suggest you read the codes first so you know what you're dealing with before you start throwing money at it then pull fuse #1 for a few minutes, take it for a drive and see if the light comes back then read the codes again.

Then you'll have a fresh code and no red herrings that might be present from old, historical, undeleted fault codes that have previously been fixed.

https://www.volvoclub.org.uk/faq/EngineOBDCodes.html

At a guess, yours is probably a 1993 car if you bought it in 1994 as an ex-demo so is likely to have the one (or two) boxes on the inner wing near the L/H suspension turret. If it's the later one with the "not-quite-OBD" socket in the centre console you'll need a code reader, available from a forum member (Loki_the_GLT) for a modest cost.

Until you read the codes, it's like playing darts blindfolded in a circular room with no lights or windows while stood on a turntable in the centre of the room.

It would be more luck than judgement if you even hit the board, never mind the bullseye (fault) and you'd end up just as dizzy with a headache!

[griston64]

96 car will be in centre console and you will need a specific reader

Sensor is on downpipe on my 96 car. If you have a blow in exhaust before cat it could cause light to come on

[Laird Scooby]

Originally Posted by griston64

96 car will be in centre console and you will need a specific reader

Sensor is on downpipe on my 96 car. If you have a blow in exhaust before cat it could cause light to come on

Thanks Mark, i misread it as 1994 he bought it as an ex-demo so it could still be a 95 or perhaps earlier - usually demonstrators are sold off at 6-12months old so it's right on the changeover.

Either way, all the information should be on that link i posted to the FAQ, could have just been a glitch on the system, sometimes happens.

[classicswede]

The lambda being the actual fault putting the light on has a less than 1/100 chance. It does baffle me that most garages first plump is to fit a "new" lambda and opt for a non working universal one to only also create a new problem

If you are getting fuel mixture faults its not likely the sensor, best bet is to live moniter the lambda to see what it is putting out. A failed one will usually read a constant 0.47v or stay close to 0.0 it should track back and forth from around 0.1-0.9v

[TonyS9]

He only says when he bought it not what year the car is. Although it only makes a differences as to how to read the codes.

If the OP doesn't even know where it is then perhaps its maybe best taken to a mechanic. It can be costly to diagnose remotely like this.

The sensor does seem the most likely at this point, but the exact part with the right connector is hard/expensive to get, so you don't want to throw money about.

You can get a cheap item for About £25 but my experience is they fail quickly.

You need a Bosch item, typically costing about £70. There are a few versions.

[Forrest]

My recollection is that a faulty lambda sensor doesn’t cause the engine to cut out. I seem to remember when mine failed it just caused the engine to run very rich and mpg to fall dramatically. I have at the back of my mind it didn’t even cause the light to come on, but I may be wrong on that point.

The engine cutting out suddenly could be due to any number of intermittent faults and would certainly have the potential to leave some, probably spurious, error codes.

Clearing the codes as suggested will probably make the lamp go out until the next time the engine splutters.

Things in my experience that can cause mysterious engine cut outs are:

Fuel pump relay
Crank position sensor
Lazy in-tank lift pump (on earlier cars)

But there are plenty of others. These are just the ones I’ve experienced personally. If the codes you pull are ignition or fuel related this might help to point you in the right direction, but in my experience probably won’t help. You’ll almost certainly have more than one code stored. They don’t all cause the lamp to illuminate.