Misfire and stuff on 04 C5 2.0i (not hpi)

[wheeler]

Would imagine it would be a 4 wire sensor on this, thought it was only the HPi that had a 6 wire sensor.

[ekjdm14]

downstream is from the exhaust manifold into the cat right, i have four wires going into a blue plug near the egr valve?

Just a small contribution from me, downstream is after the cat. If there's a problem with this sensor or it's wiring it would throw up the anti-pollution fault too as it's purpose in life is to monitor the performance of the cat. (of course, IMO it would be wise to check the condition of the cat as well in this case since the car's been run with a persistent misfire which may (or may not, hopefully) dump raw fuel into the exhaust, melting the innards and potentially causing all sorts of other problems if it blocks the exhaust further down.

Hope this is of some use

[deian9]

Marc, thats awesome stuff, thanks so much. Just a few questions...

1334 is an injector I presume (going by the picture) and is grounded by pin2 (1324) through MM01. So a signal to it travels along to pin1 of each of the O2 sensors? Really? How is an injector triggered?
What is item 1270 and where is MM01 located?

[deian9]

downstream is from the exhaust manifold into the cat right, i have four wires going into a blue plug near the egr valve?

Just a small contribution from me, downstream is after the cat. If there's a problem with this sensor or it's wiring it would throw up the anti-pollution fault too as it's purpose in life is to monitor the performance of the cat. (of course, IMO it would be wise to check the condition of the cat as well in this case since the car's been run with a persistent misfire which may (or may not, hopefully) dump raw fuel into the exhaust, melting the innards and potentially causing all sorts of other problems if it blocks the exhaust further down.

Hope this is of some use

Ah, that is something I did think. Which is why the catalytic converter fault came up? But surely it can only detect this fault through comparing the two O2 sensors and not through physical inspection (or by monitoring an expected temperature?).

Also, and this is just a thought... i think mine is more of an anti-misfire (as oppsed to an actual misfire)... in that it fires a spark but doesn't inject fuel, so maybe the catalytic converter is ok

[ekjdm14]

Yes my thought initially is it may have shut down the injector to protect the cat, the fact it's flagging a fault for the cat is most likely down to the dead downstream O2/or it's wiring.

All the downstream O2 sensor does is compare the level of oxygen in the exhaust to the reading from the upstream one, so if it varies a lot from it (i.e. because it's heater circuit appears to have failed) it'd throw the anti-pollution/cat faults.

There's a fair-to-middling chance the cat has survived thus far, but with potential multiple faults it'd be on my personal to-do list to drop it off the car and visually check it's not damaged/melted. May even make removal/testing/replacement of O2 sensors easier.

Also, if the sensor threads do disintegrate on removal all is not lost. Provided the pipework is in reasonable shape the old boss can be sliced off and a replacement welded on, they're dirt cheap and a lot better than replacing sections of otherwise serviceable exhaust.

[GiveMeABreak]

Marc, thats awesome stuff, thanks so much. Just a few questions...

1334 is an injector I presume (going by the picture) and is grounded by pin2 (1324) through MM01. So a signal to it travels along to pin1 of each of the O2 sensors? Really? How is an injector triggered?
What is item 1270 and where is MM01 located?

1270 is the Carburettor or throttle housing heater resistor.
1324 is the negative injector control.

Deian - To make it easier, I'm emailing the wiring diagrams over in a tick. Also, have a squiz over here on the Wiki, I've already put most of the PSA electrical component and wiring codes here. The 'list of components' sections 1-3 should have the codes and are in numerical order where possible.

PSA Electrical Wiring Codes on the FCF Wiki]

[CitroJim]

Thanks Jim, I can't recall it either, I tried to sign up with my old username of deian but it failed so it may be dormant somewhere, so it could be that. But for now, I'm happy to leave it as it is.

No worries Dei, that's fine Hope the C5 issue is soon resolved Sadly I can't help as my knowledge had not moved on much from Xantias These C5 devices are a complete mystery to me!

[Paul-R]

Also, if the sensor threads do disintegrate on removal all is not lost. Provided the pipework is in reasonable shape the old boss can be sliced off and a replacement welded on, they're dirt cheap and a lot better than replacing sections of otherwise serviceable exhaust.

Not an option for me on the 106 unfortunately as the upstream lambda sensor screws into the cast iron manifold!

[deian9]

I had a quick look around today and noticed the pre-cat O2 sensor was not tight. So I thought it was solved. I tightened it up started her up and back came they anti pollution fault and misfire.

But it does seem more keen to go back to 4 cylinders when it does misfire.

So either the sensor has been shaken and broke or the post-cat sensor is also dodgy in some way.

When it dries up a bit I'll go underneath amd have a look. But thats not before I check the wiring.

Is the resistance of the two O2 heaters supposed to be the same? (if they both have heaters).

So I think the misfire is the car saving itself? A limp mode or sorts but not the proper one as I haven't been blatantly told it's in Limp mode in any way.

[xantia_v6]

I am 100% sure that the misfire is not due to any action of the oxygen sensor. The oxygen sensor can only tell the ECU if the overall mixture is rich or lean, and the ECU does not trim cylinders individually.

It is most likely that you have a broken wire or connector between the ECU and injector. Maybe the Lexia live data will tell you something.

[ekjdm14]

I had a quick look around today and noticed the pre-cat O2 sensor was not tight.

This would tell me, apart from anything else, that somebody's been here before trying to solve things. Those sensors normally seem to be FT so for it to be loose suggests it's been out/replaced before. If someone has been stripping things down and not managed to retorque an O2 sensor I think you'd be well advised to have a thorough look through all the connectors/wiring to the sensors, injectors, coil packs etc as well as checking everything is bolted down correctly.

If the sensor has been replaced by someone who couldn't remember to tighten it, then it may also be a cheap aftermarket item so, again IMO it'd be worth checking it's origin/function compared to OE specs as aftermarket kit can be very shoddy in this area.

I agree the upstream O2 won't be responsible for all the current symptoms, but they possibly could have been either aggravated or even caused in full by someone messing where they shouldn't have been.

[CitroJim]

IMO it'd be worth checking it's origin/function compared to OE specs as aftermarket kit can be very shoddy in this area.

Yes, I've been caught out with cheap generic oxygen sensors in the past; their lives can be measured in weeks...

And yes, an oxygen sensor, if it has any pride, will be FT!

[deian9]

Indeed... I'm a firm believer in buying proper OEM quality stuff. Most people will tend to cut corners with these kind of stuff (xantia drop links being a classic example). It's just false economy. Buy cheap, buy twice. The good news is the sensor thread is intact as far as I can feel (literally 'as far' as my arm could reach down to tighten it by feeling from top of the engine bay), I did use a spanner to seal it up as much as possible afterwards).

I'll be able to take it out fine and make some checks on it indoors. With some luck the rear one will be just as easy (famous last words).

Does anyone know is they are serviceable in any way? Or do they have some exotic sealed components thats make it worthless to take appart and attempt to fix?
But the fact that there are issues with the O2 sensors explains why it drinks fuel. It's on par with that black XM 2.0i CT that I had. But I do like the car, it's pretty quick off the mark when it fires on all cylinders!

It's just my luck that the weather isn't so good and the days are quite short. So until the weather dries up a bit I'll sit tight and I'll go through the receipts that came with the car when I bought it.
(the issue I have is that I live in Liverpool now and I have to park my car in the street, where as before in my Xantia V6 and XM era I lived at my parents in Wales (or not far from them), Dad has a drive, a garage, and a lot more tools )

[CitroJim]

No, sadly Dei, the O2 sensors really are not amenable to being repaired at all. Definitely sealed. They are in effect small batteries that use oxygen as an 'electrolyte'. They generate a voltage ranging between very little and nearly a volt depending on the level of oxygen around them...

A condition that's awfully hard to simulate for test purposes and made more difficult in that they need to be very hot (around 800 degrees) to work at all...

[deian9]

Hence their price then I guess.