Cat or Lambda sensor?

Exhausts, Air filters and the like.......
WesFriedel
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Cat or Lambda sensor?

Post by WesFriedel »

Recently had engine management light on and the fault was emissions from CAT too high....Can anyone tell me if this does actually point to a dodgy cat or if it could be the lambda sensor?

Don't want to replace one and it turns out to be the other!!

Thanks

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gazza82
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Re: Cat or Lambda sensor?

Post by gazza82 »

Exhausts can be fun .. have you got any holes or blows? They mess up the lambda readings ... so can fuel. Cheapo supermarket fuel can up set the readings too.

And some cars have more that one lambda .. our 2.0 has one before and one after the cat .. and they are slightly different so two part numbers.

Have you had the car long? If not it could be the lambda is wrong ... Bosch sensors are expensive, and fleabay offers are not always the right resistance. I had an NTK fitted to a car and constantly got random lambda errors .. swapped it out for a Bosch and ... faults went away.
Family Fleet: ex-Cayman Green 206 CC 2.0 LE, Indigo Blue 206 1.4 HDi Hatchback, Subaru BRZ Auto, Alfa Romeo MiTo

WesFriedel
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Re: Cat or Lambda sensor?

Post by WesFriedel »

I did have a blow on the rear box but that's been filled now.....I did fill it after resetting the EM light so I guess could have started the problem again? Bought the car 3 weeks ago, 2001 (Y) 2.0 model

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Capncol
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Re: Cat or Lambda sensor?

Post by Capncol »

As you have recently bought the car, I'm guessing you don't know previous history.
First thing I would try is to take it for a long hard run and get the exhaust *cooking hot*. This will help burn off any residues that have built up in the cat.
If that doesn't work, you can either get the fault codes read, or check the output from the lambda with a meter. I can tell you how if you have access to a digital meter.
Reading the codes is better as you may have another problem causing the fault, such as a misfire.
Cheers Col.


206cc 1.6ltr (Wifes toy)
Mercedes ML (workhorse)
Corvette C3 (my toy)

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gazza82
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Re: Cat or Lambda sensor?

Post by gazza82 »

WesFriedel wrote:I did have a blow on the rear box but that's been filled now.....I did fill it after resetting the EM light so I guess could have started the problem again? Bought the car 3 weeks ago, 2001 (Y) 2.0 model

Exhausts on that model seem to be poor ... we've replaced ours and it's now cracked due to bottoming out on a speed-bump we think. Caused fun on the MOT but gungum saved the day! That's fallen out now, so I have to do it again or take it off and get it re-welded. BOSAL exhaust as well, so not cheap!
Family Fleet: ex-Cayman Green 206 CC 2.0 LE, Indigo Blue 206 1.4 HDi Hatchback, Subaru BRZ Auto, Alfa Romeo MiTo

WesFriedel
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Re: Cat or Lambda sensor?

Post by WesFriedel »

Error code is P0420 - any ideas please?

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Capncol
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Re: Cat or Lambda sensor?

Post by Capncol »

That has pinned it down to cat or lambda for sure. Have you got a digital meter and I will tell you how to check the lambdas?
Cheers Col.


206cc 1.6ltr (Wifes toy)
Mercedes ML (workhorse)
Corvette C3 (my toy)

When requesting help of a technical nature, please give as much detail of the fault as possible along with details of exact model, engine size & type, gearbox, year, mileage, and any relevant work carried out to try to solve the problem to help us help you.
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WesFriedel
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Re: Cat or Lambda sensor?

Post by WesFriedel »

No, fraid not. I know my uncle does though if you could send me instructions please?

Any chance it could be the coil pack? Today its not quite ticking over as smoothly as it has been.

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Capncol
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Re: Cat or Lambda sensor?

Post by Capncol »

No. That code is definitely lambda/cat
Cheers Col.


206cc 1.6ltr (Wifes toy)
Mercedes ML (workhorse)
Corvette C3 (my toy)

When requesting help of a technical nature, please give as much detail of the fault as possible along with details of exact model, engine size & type, gearbox, year, mileage, and any relevant work carried out to try to solve the problem to help us help you.
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WesFriedel
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Re: Cat or Lambda sensor?

Post by WesFriedel »

Tell a lie....I just remembered I have a digital meter sat in my garage.

If you forward the instructions ill take a look into it.

Thanks

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Capncol
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Re: Cat or Lambda sensor?

Post by Capncol »

What engine / year is it?
Cheers Col.


206cc 1.6ltr (Wifes toy)
Mercedes ML (workhorse)
Corvette C3 (my toy)

When requesting help of a technical nature, please give as much detail of the fault as possible along with details of exact model, engine size & type, gearbox, year, mileage, and any relevant work carried out to try to solve the problem to help us help you.
Better still, put the details in your signature.

WesFriedel
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Joined: Tue Jun 18, 2013 7:29 pm

Re: Cat or Lambda sensor?

Post by WesFriedel »

2001 (Y) 2.0 petrol

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gazza82
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Re: Cat or Lambda sensor?

Post by gazza82 »

That's the code I got when our engine management light came on. I used PP2000 with the correct cables so it should be correct but never did get it to tell me which one of the two it was reporting.

A few months later, the exhaust fell off, and a new one has stopped the code appearing. On the 2 litre this includes a new cat as this is part of the front section (manifold to rear silencer box is one-piece).


I'd double check the exhaust system for the tiniest of holes .. unless like ours you have just left part of it down the road :big-grin:
Family Fleet: ex-Cayman Green 206 CC 2.0 LE, Indigo Blue 206 1.4 HDi Hatchback, Subaru BRZ Auto, Alfa Romeo MiTo

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Capncol
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Re: Cat or Lambda sensor?

Post by Capncol »

To check top lambda (by the exhaust manifold) Take the plug apart and identify the two wires of the same colour. These are the heater wires. Measure towards the O2 sensor, the resistance should be under 30 ohms. If it is over or open circuit, sensor is u/s. Next, put a meter across the other two wires, and with the engine running, rev the engine, you should see a small fluctuating voltage around 3-5v (ish) If you get no voltage, or no fluctuation as you rev the car, the sensor is u/s. If it's ok, put the plug back in

Now test the sensor after the cat in exactly the same way, except this time the voltage should remain fairly stable. If it fluctuates as much as the first sensor, then the cat is u/s.
Before you change the cat (if that is the problem) check for what has caused it to fail.
Wrong fuel?
Burning oil?
Head gasket failure causing antifreeze to get in?
Driven through deep water?

Let us know what you find.
Cheers Col.


206cc 1.6ltr (Wifes toy)
Mercedes ML (workhorse)
Corvette C3 (my toy)

When requesting help of a technical nature, please give as much detail of the fault as possible along with details of exact model, engine size & type, gearbox, year, mileage, and any relevant work carried out to try to solve the problem to help us help you.
Better still, put the details in your signature.

WesFriedel
Posts: 15
Joined: Tue Jun 18, 2013 7:29 pm

Re: Cat or Lambda sensor?

Post by WesFriedel »

Thanks for the info....Before I try this is it possible a leak in the system could through up this error? Ive just been out to inspect the system knew there used to be a leak near the rear box. Ive tried to undo the clamp on the join and it snapped off - its that rusted!

Now the back box and pipe are apart I think either one of them has corroded too much....However I don't know what the two ends should look like. Ive taken photos but not sure if anyone could tell me which end needs replacing if any if I emailed them over?

Thanks

Wes