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Engine Depollution Failure - Warning light |
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Valleybuoy
 
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   Member No: #1069
Location: England |
So the light (which has intermittently come on and off) is now truly on. Citroen looked at it, and diagnosed a temp rear EGL(?) valve failure. They cleared the code, but it came back almost immediately. Citroen are saying it would cost >£900 to replace the valve. They warned that if the light came back on, car could enter Limp mode (Which it has not). Any idea what this valve does? Car running fine with no obvious issues. Can anyone recommend an independent specialist (Basingstoke/ Reading/ Woking triangle) who could resolve for a more reasonable cost? Thanks! |
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frozenbeard81
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 Member No: #2503
Location: Bagshot |
Give PTS a call, based in Wokingham. Reasonable priced and knowledable guys. | ||
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gmerry
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  Member No: #21
Location: Scotland |
Hi Valleybuoy, I'm guessing we are talking about the rear Exhaust Gas Recirculation (EGR) valve. If the rear valve has failed shut, no running problems. If the valve has failed open, it will cause the engine to run very badly. Do you have any hestitation, stumble, flatspot, poor idle etc problems? If no, more than likely it will be closed. Easiest diagnosis if you don't have access to Lexia etc is to place a wood dowel on the valve bodies and get an assistant to turn off the engine, both valves will make a loud click, click , click noise if healthy. Keep in mind that if the rear valve has failed, front will need doing soon too (see my posts on the subject). Regards getting these replaced, might be worth speaking to BL Autos and asking for a quote. Regards G |
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Valleybuoy
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Member No: #1069
Location: England |
Thanks G & Frozenbeard. Based on the above, yes, it's the EGR. I assume failed closed, as the car is running beautifully, (best it ever has). Interestingly, I've had trouble heating the car internally which may be linked. I've sent the details to PDS Wokingham, and will also ping BK autos. Will update on progress! |
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Jodyone
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 Member No: #1240
Location: Cornwall |
Exactly the same situation as me, it's running great so I assume the EGR failed closed. I'm replacing it as soon as the hose clip pliers that gmerry recommended turn up! | ||
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gmerry
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Member No: #21
Location: Scotland |
Hi both, I replaced the front EGR valve (as per Lexia diagnostics) and once this was working the rear valve immediately failed. My theory is that the front valve had been failed for a long time (10 months) and during this time, the engine management switched off the EGR function which was fine in so far as engine running goes. However, with a new working front EGR valve, the engine management now requests the rear valve to start modulating which it doesn't respond to because it has been sitting in the same position for a very long time (or there was a unrevealed failure of the rear actuator all along). What I'm saying, is that if you are paying someone to change an EGR valve, the age of the car and the failure patterns emerging, suggest you should do both while you are at it. This is because there is a fair amount of dismantling which will be common to both jobs. Regards G |
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Valleybuoy
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Member No: #1069
Location: England |
GMerry - interesting. What do the EGR valves actually do in terms of performance/ running? ie what's the point of them? |
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gmerry
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Member No: #21
Location: Scotland |
EGR (Valves) allow the engine/vehicle manufacturer to comply with EU directives. The recirculation of combustion products lowers the peak combustion temperatures at the Molecular level* (note this is NOT the same as combustion chamber temperature), thereby reducing the amount of NOx. A diesel cannot use a 3 way catalyst unlike a petrol SI engine, hence Euro 3, Euro 4, Euro 5 diesel engine dependence on increasing amount of EGR and introduction of cooled EGR in order to meet legislation. Regards G * Need to look at Gibbs Free energy and free radical combustion chains. |
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Valleybuoy
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Member No: #1069
Location: England |
G - makes sense. Even to a non-tech-head like me! Is it an MOT failure therefore? |
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Valleybuoy
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Member No: #1069
Location: England |
Additional thought? If the EGRs are not an MOT Failure - why not just remove altogether when they stop working? Feels like an incumbrence rather than an enabler. Then the only issue would be that the warning light would always be on... |
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Jodyone
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Member No: #1240
Location: Cornwall |
Valleybuoy wrote ... G - makes sense. Even to a non-tech-head like me! Is it an MOT failure therefore? Apparently not- I checked with my MOT guy (it's next week) and he said as long as the emissions are fine there's no problem. EGR disabling is not a new idea and is commonly done- I think there's a long-running thread about it on here. My other car from 1984 has -had- an EGR valve and I removed it and fitted a blanking plate, partly because it had long become a sculptural object in rust. Modern cars, such as the C6, are much more sensitive to such fiddling and the short answer is- "It might not be as simple as that". Also, MOT regs may change in the future. I'm replacing the faulty valve on mine simply because I depend on this car and I'd prefer it to operate as close to the factory specs as practically possible. |
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321dave
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Member No: #614
Location: Dublin |
Hi G, would you have any photos of the dismantling undertaken when you changed out the EGR valves? If all is clear Lexia wise (global scan clear) would it be safe to say the valves are working correctly or could they be stuck closed and that wouldn't show up as an error on a global scan? I'm still wondering about mine and I'll be in and around that area very soon doing the timing belt. | ||
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gmerry
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Member No: #21
Location: Scotland |
Hi all, MIL light showing is an instant MOT failure. When my EGR failed closed, the MIL illuminated and clearing the fault only worked for about one restart. Regards G |
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David Hallworth
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   Member No: #90
Location: Glasgow |
EGR valves aren't needed for an MOT. The rear is apparently the easiest to change, the front takes around 5 hours labour from what I've heard. Robert at BL Auto's in Welwyn Garden City has done a load of these. I also know someone who had his EGR fail in the shut position, he left the knackered valve in situ and had the car remapped and told the ECU that it didn't have any EGR valves. He's had no problems in 2 years since, and as a result of his remap is getting far better economy. David. |
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frozenbeard81
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Member No: #2503
Location: Bagshot |
5 hours? I seriously doubt that. Unless you have to strip the entire car down. | ||
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