Oil inside wiring loom!!!

[dwmoney]

Looking for some advice please, I have a 2016 T6 4Motion on 60k miles which has developed some fault codes. It threw up a flashing coil light last October and the code reader showed P2102 (Throttle actuator control motor circuit low) P2100 (Throttle actuator control motor circuit open) P2101 (Throttle actuator control motor circuit range / performance). During a journey home (around 100 miles) these error codes disappeared and the coil light went out but then would intermittently re-appear now and again. Everything seemed fine in terms of how the van was driving so I figured it was probably a sensor playing up. Recently I have had the clutch and fly wheel replaced and once the garage had put things back together these fault codes returned along with the coil light and engine management light. I said to the garage that I've seen the codes before and they may go away by themself so I took the van and continued using it. After a couple of weeks the codes hadn't gone so I returned the van to them to investigate. They started with diagnostics and then advised after speaking to VW that we change the throttle body. This was done but still have the error codes. They then started looking at the wiring and have found that there is oil in several electrical connectors and the wiring loom connector that plugs into the ECU. They said it appears that oil has got into the wiring loom itself and has flowed inside the cables and into the connectors. They have looked at the oil pressure sensor and the oil level sensor and both electrical connection are dry (no oil) so possibly ruled them out as the source. They have not found where this oil has come from or how it got into the loom but there is evidence of a spraying oil leak in several places such as hoses and on top of the starter motor. They have cleaned all the electrical connectors that they can get to easily and put everything back together (including putting the old throttle body back on) and the error codes/engine lights are all on as before. VW have said it needs a whole new wiring loom (£3k + before fitting!) and that may ultimately be what ends up happening but the source of the leak still needs to be found first which is a bit of a mystery... Sorry for the long winded story but has anyone ever come across a situation like this or have any words of wisdom to aid me please? Photo shows oil on ECU connector.

 

[Sioux101]

If it was me, spray to remove oil from plug. Check oil level and see if it improves? Could be spilt oil by someone not fessing up.

 

[MK2Golf24v]

You need to check all the sensors. One will be leaking for sure.

I have a Q5 that pumped water into the loom via the header tank level sensor connection. It’s amazing how far it can spread!!

 

[dwmoney]

If it was me, spray to remove oil from plug. Check oil level and see if it improves? Could be spilt oil by someone not fessing up.

Something I forgot to mention was the throttle body errors are also preventing the system from regenerating the DPF so driving it is not a good idea. I can clear the codes using my simple code reader but the instantly return when you start to drive. The garage it was in has cleaned the connectors and plugged everything back in to no avail.

 

[Hakon]

Had exactly the same issue on an E63. The cam sensor design / plastic allowed oil to pass through the sensor and into the wiring loom, wicking it's
way to the ecu and pretty much everywhere else causing misfires.
The sensors were changed and brake cleaner sprayed liberally all over the place. The alternative was a new loom

Can only suggest getting someone else than VW to hunt out the source.

 

[dwmoney]

Did you end up replacing anything or did the clean up process stop the misfires?

 

[catfood12]

I've seen this too before OP, capillary action draws the oils a long way down the loom, as @MK2Golf24v says. I'm with @Hakon on the fix; Use brake cleaner on all of the connectors to degrease. It will dissolve the oil and then evaporate, so no need to rinse with anything. Clean the loom and sensor connectors. Hopefully you'll come across a super oily wet plug which should point you to the leaking sensor. Good luck! A new loom would go the same way until the source is found.

 

[Hakon]

Did you end up replacing anything or did the clean up process stop the misfires?

I didn't hang onto it much after the issues arose as I was expecting the MB extended warranty to come to the rescue but needless to say they didn't want to know anything about it.

The oil ingress in the sensor wasn't the easiest to spot as it was subtle and not as such flooded in oil.

 

[teamfly]

Had a similar issue recently with our audi a4 1.8 tfsi.
Ours was a coolant sensor on gearbox which leaked into the loom , under pressure I suppose . Found its way up to the ecu & wrecked it . Hopefully oil will cause you less damage .

 

[Jonbob]

Hey DWMoney, just wondering if you managed to find the leak and if so what it was? I have the exact same issue on a T5.1 the oil is only in the smaller connector on the ECU and the oil pressure sensor is dry.

 

[dwmoney]

Hey DWMoney, just wondering if you managed to find the leak and if so what it was? I have the exact same issue on a T5.1 the oil is only in the smaller connector on the ECU and the oil pressure sensor is dry.

It turned out there wasn’t oil in the loom after all. It appears that at some point its been driven (or at least had the engine running) with the oil cap off which has sprayed oil over the engine bay. Not sure if that was what caused the faults to appear but after a steam clean, full inspection of the loom, clean up of connectors and re-assembly its now happy again.