Please help - fault diagnosis

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Picamik
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Please help - fault diagnosis

Post by Picamik » 26 Sep 2016, 19:00

Folks,

In my younger days, I did a fair bit of stripping engines, and even reconditioned an automatic box once - but that was all when cars still had carburetors, points and distributors. I don't know much at all about diesels apart from their theoretical principles.

Now, after 10 years since new, I have had a run of bad luck with my Citroen Xsara Picasso 1.6 HDi (2006).

The car had never given any trouble, but at 10 years, I replaced the timing belt, which involved moving the steering fluid reservoir on its rubber tubes, which dislodged a but of dirt that jammed the pressure by-pass valve in the steering pump. You can't get the valve, so I replaced the pump, which involved uncoupling 4 electrical connectors (I think to do with the a/c and the EGR - though I'm not sure), and after that job, the engine light came on, so I suspected a connector problem. After two very short trips, it went out again, but it left me with poor acceleration, and I have also noticed a drop in the dashboard indication of fuel consumption (down from 60 MPG to 42.8). I bought a cheap scanner on Ebay, and the diagnostics showed ...

Code: Select all

stored trouble codes                            |    pending codes
                                                |
p0100 mass volume airflow circuit malfunction   |    p3008 unknown code
p0299 turbo underboost                          |    p0299 turbo underboost
p0238 turbo sensor A-circuit high               |    p1351 unknown code
p1351 unknown diagnostic code

I cleared these codes to see if the poor performance was due to the EMU limiting it due to the stored codes, and took the car for a 5-mile burn. Performance was still poor, and when I got home again, I re-checked the fault codes. There were none, but the three "pending" codes were back again. They are P3008, P0299, P1351.

The possibilities are :
1. something went wrong when I disconnected / reconnected the electrical connectors
2. I made an error while changing the timing belt. I know that bad valve timing screws with performance - I once bought a Mini with poor performance, and found it was one tooth out on the timing chain. On the Citroen, I marked the belt and pulleys with paint, and was very careful to fit the new belt exactly as the original one had been fitted. However, could somebody tell me whether bad valve timing would cause error codes to be generated? As I don't currently have any, can I assume that the belt is definitely not a tooth out?
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Re: Please help - fault diagnosis

Post by Stickyfinger » 26 Sep 2016, 19:33

"Looks" like a MaF sensor problem to me.....

What code reader are you using ?
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Re: Please help - fault diagnosis

Post by Picamik » 26 Sep 2016, 20:03

The reader is called "ECU SuperScan" for all OBDII protocols. Professional Version 2. I'm running it on a 30-day trial of PCMSCAN.
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Re: Please help - fault diagnosis

Post by Stickyfinger » 26 Sep 2016, 20:09

It really should be read via a Lexia, this is the tool best suited to PSA cars, other reader are well know for poor fault reports....(about £150 and the best investment if you are keeping the car)

That said, still looks/sounds like a MaF fault. Did you damage it by chance ?
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Re: Please help - fault diagnosis

Post by Picamik » 26 Sep 2016, 22:20

Hmmm... Fault codes are generated by the car's management computer, and all the diagnostic pod has to do is read them. As I have spent my life in computers, I'm quite savvy about how digital communication works, and if this scanner is giving me these codes, I have no reason to believe it is making them up. Similarly, if the car's management computer is developing fault codes, it's quite a trivial operation to read them, so I have no suspicion that warnings are there but not being read. If it was an analogue system, then drift and inaccuracies come into play, and one device may well be different from another - just as analogue recordings of music are not the same as the original. However, a digital recording of a digital medium (eg. a music CD) are exactly the same as the original, and I'm sure any fault codes displayed on my PC are the exact copies of those in the ECU.

I must confess, I don't know where the MAF is on my car - though the connectors I disconnected (there were four of them) were all on large-diameter plastic tubes that run across the top of the engine. I think one of them was for the EGR, as it was on a tube that appears too to the turbo. I'll find out where it is and check on it.

I wanted to send a picture of the engine showing the connectors in question, but the "img" tool doesn't seem to work.
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Re: Please help - fault diagnosis

Post by Hell Razor5543 » 26 Sep 2016, 22:28

The problem is that the PSA Group do not exactly adhere to the agreed protocols, some generic OBD readers get confused. However, the Lexia clones can read and make sense of the protocols, so can produce meaningful results. However, the Lexia can do a WHOLE lot more than a generic reader, including (but not limited to) programming in new keys, and display live engine data.

The MAF is (as I understand it) on the air feed after the filter box (but I could be wrong). This links supposedly shows a MAF on a 1.6 Picasso;

https://i.ytimg.com/vi/6FBsnmwEfqk/maxresdefault.jpg
Last edited by Hell Razor5543 on 26 Sep 2016, 22:31, edited 1 time in total.
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Re: Please help - fault diagnosis

Post by Stickyfinger » 26 Sep 2016, 22:30

There is a reason PSA use the Lexia....I will let others with better knowledge than me reason it.

The MaF is on the intake just after the Air Filter, it looks like this
Image
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Re: Please help - fault diagnosis

Post by jimmymarsbar » 27 Sep 2016, 20:58

Hell Razor5543 wrote:The problem is that the PSA Group do not exactly adhere to the agreed protocols, some generic OBD readers get confused. However, the Lexia clones can read and make sense of the protocols, so can produce meaningful results. However, the Lexia can do a WHOLE lot more than a generic reader, including (but not limited to) programming in new keys, and display live engine data.

The MAF is (as I understand it) on the air feed after the filter box (but I could be wrong). This links supposedly shows a MAF on a 1.6 Picasso;

https://i.ytimg.com/vi/6FBsnmwEfqk/maxresdefault.jpg


I agree, the 307 is very temperamental on PP2000 and Diagbox, so I believe there is a little bit of "creative license" used when the ECU maps, pathways, protocols, diagnostic software etc are written.

I have a delphi, which is the best £ for £ generic set up I have used, and even that will struggle to capture absolutely everything that Lexia would on a Citroen, VCDS for VW and it's counterparts etc. Even on the OBD generic codes, there's a level of uncertainty.
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Re: Please help - fault diagnosis

Post by Picamik » 28 Sep 2016, 21:15

Solved it! In replacing the steering pump, I had to remove a molded plastic structure that appears to be a plenum of some sort, with four 3" diameter plastic tubes leaving it, and two butterfly valves with electrical connectors to control them. The tubes that leave this assembly are connected by rubber tubing and large hose clips. Naturally, I had removed the hose clips, and in reassembling it I had omitted to tighten one of them. The rubber hose was pushed over the plastic and the hose clip was in place, so it wasn't obvious visually, and when I found it, I was pretty dubious that it could be the root of my problem, but - long story short - it was. Performance is back to what it was before the job, and I have cleared the fault codes, and they haven't come back again.
In the image below, the gubbins I removed is surrounded in yellow, and the hose clip in question is arrowed in red.

Image

I'd like to thank those who gave so generously of their time and effort to help me. Even though the fault was finally something different, the info given here was valuable insight, and got me looking in what turned out to be the right places.
Last edited by myglaren on 28 Feb 2017, 23:08, edited 1 time in total.
Reason: Fixed image link
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Hell Razor5543
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Re: Please help - fault diagnosis

Post by Hell Razor5543 » 28 Sep 2016, 21:32

Well done.
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