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post #29 of (permalink) Old 29th July 2013
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Re: 2001 Renault Laguna II diesel "Yellow Glow Plug and Electronic Fault warning ligh

My name is Ascalon and My Lag II DCi has been having the injection warning light/limp mode issue for quite some time.
I changed the fuel filter, cleaned the EGR valve and the MAF sensor and did a minor service of fluids and filters, to no avail.
I tested the glow plugs and they were buggered so I changed them.
I found that the MAP sensor was a little dodgy so I changed that too.
It seemed to make a difference and then it was back and worse than ever.
I went to an ex-dealer who had all the experience and diagnostic gear.
He hooked up the CLIP reader and it said throttle pedal open circuit fault.
He wired in a new connector from an old loom. No good. Looked like the fault was with the pedal.
Got one from a low mileage car, put it in and tried it. If anything it was worse.
Then I sat down and wrote down the symptoms and worked back from there.
Cutting a long story short, the car often started from cold and drove no problem until it needed to be re-started from warm, after which the fault would appear and cause the problems.
The warning light rarely stayed on, but would come on and flicker and then cause the power loss and limp mode intermittently making for interesting experiences, especially cruising on motorways.
More reading and research turned up the idea of water ingress into the ECU, so I thought I***8217;ll have a look.
I took the ECU out and the pins were not corroded, but there was this weird stuff stuck to several pins on one of the connectors.
It looked like silicon sealant that had not gone off completely. When I took it out, it was still jelly like, but in the hand, with heat, seemed to go quite hard (Oooer missus!).
A large amount of electrical contact cleaner later, and a small brush, and I had cleaned it all off.
I put it back, and reconnected everything and did a 45 minute each way trip, including motorway cruising without so much as a flicker of the light.
I thought I might be onto something, then looking for more info, I found this post in a thread about petrol Lag IIs with a similar problem.
"Now I***8217;m told by a reliable source that when they are first put together at factory they spray a anti corrosive gel onto the plugs and contacts to prevent corrosion or water ingress, after a few years this gel sets rock hard and then loses it properties and hey presto u get corrosion and duff contacts on the plugs n pins at the ECU under the battery tray"
I nearly sprayed coffee all over the screen.
That was exactly what I had seen in mine! Apparently, the stuff goes off and causes continuity problems that the ECU reads as faults in the respective components.
So, if you are hunting any kind of warning lights on a Lag II is more than a few years old, do nothing, replace nothing until you whip out the ECU and check the connectors and pins for that gel **** and clean them up first.
Then clear fault codes and then start your testing, otherwise you may end up hunting gremlins that are mere phantoms.


Currently in Ascalon's garage:
2003 Renault Laguna II 1.9 DCi
Ascalon is offline  
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