Mk2 Running /cutting out problem........Help Please.

Hi guys,

First post although a long time lurker.

Hope someone can help.

My Son has a 2000, Mk2, 1.9sdi Caddy, about a month ago he drove to work without any problems, 8 hrs later when he tried to start it, it would turn over but not start. I went to his work later that night and found it wasn't getting fuel. After some checking on various forums I picked up a 109 relay from Europarts (VW didn't have any) put it in and it started first time. Everything has been fine for the last 3 weeks until Friday when after driving about 20 miles the throttle stopped responding and would only run at 30 - 40 mph, the coil light also flashes continually when this happens. I borrowed a Snap On diagnostic machine from my mate and it came up with

Accelerator Position Sensor G79 Not a plausable signal Intermittent 00777

I replaced the europarts relay with a genuine 109 relay from VW (Grey one), again he drove about 20 miles and the throttle stopped responding (Coil light flashing). If he pulls over and waits for 5 mins or so the van starts and runs fine for a few miles then does the same again. On checking the relay when he pulls over it is extremely hot.

At the weekend I removed the ECU and cleaned it with Isopropanol and cleaned all wiring connectors and earths within the engine compartment, we then took the van for a good run without any problems. This morning he took the van to his work (37 miles) again no problem, then tonight he drove it for 4 miles and it went into safe mode.
Could it be the ECU?, would a nacked ECU cause the 109 relay to run very, very hot?. Anyone got a wiring diagram? so that I can check exactly what systems run through the 109 relay.

Has anyone had a similar problem?.

Sorry about the long post, tried to include as much detail as possible.



Les

the code is giving you a clue as to whats probably wrong, why are you ignoring it. ACCELERATOR POSITION SENSOR... not a plausible signal. when it does it again, plug in the snap on machine, go to live data and read the accelereator position.

Quote:

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Originally Posted by zollaf

the code is giving you a clue as to whats probably wrong, why are you ignoring it. ACCELERATOR POSITION SENSOR... not a plausible signal. when it does it again, plug in the snap on machine, go to live data and read the accelereator position.

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Sorry forgot to say, I replaced the TPS with a known working one with no difference.

ok, so have you checked the wiring to it. the clue is in the code and theres not a lot that can cause a code like that other than the tps. like i said, hook computer up and drive until it breaks down then see what the tps is reading. it should be 100 % when foot to the floor.

Yes I checked the wiring and plug, everything appears o.k.. The Snap on Diagnostic tool only reads the stored faults, it doesn't give you any values.

then you can go no further with diagnostics unless you can get hold of a better computer that reads live data.
relay 109, presumably the ecu power relay does only power up the ecu, nothing else goes through it. they do suffer dry joints and do get warm.
you could try another ecu, but you will still need a better computer to code it in and do the immobiiser, so you would be better off checking the tps reading with it first. this is the thing with modern cars, you need an expensive computer to fix them, no choice, unless its a vw where you can purchase a connector and download vcds to a laptop. have a look on the vcds map, see if there is a member local to you who you meet up with. you need 10 posts to pm them though... so get posting...

O.K. will do, many thanks.