Is there a "towing" ECU in my D4?

**gavinwibrow** · 20th August 2021, 12:09 PM

Issue
Did a good Samaritan act 2 days ago and reluctantly used jumper leads to start one of the local carer guys in his little petrol car after the iTech booster/starter again proved its "limited usefulness". I very carefully followed to the letter the LR manual instructions.

Problem - after getting him started and as I was removing the first black lead on my donor car, the red lead jumped off the battery and there was a spark somewhere in the engine bay whilst I was otherwise engaged trying to safely clear both leads away from under the bay. Oh no I thought to myself, this could be expensive!

2 days later, everything seems to work OK except for trailer/caravan lights. Tried both van and trailer and got the same results so the problem is unlikely to be their wiring playing up.

Stage 1 was to check D4 fuses and found one 10A blown in the set under the lower glovebox, and about 3 other trailer related fuses in the same set showing some evidence of burns on the blades, but none "defused".

Went down to talk to my local sparky and to book in for a more comprehensive checkout. The boss is away for 4 weeks getting re-kneed and his 2IC does not claim to be an LR expert but suggested he thinks there is an ECU to control the group of trailer operations, and that might be damaged.

Car is booked in for next Tuesday, and any comments/suggestions from the gurus here please? I am supposed to be taking the bride visiting wild flowers in 7 days time pulling the brick, so need everything working.
Cheers Gavin

**DiscoJeffster** · 20th August 2021, 12:16 PM

No there isn’t but I recall there may be fuses on at the rear where the trailer harness adds onto the main harness. You might need to dig into that wiring at the rear and check there too. I may be incorrect on the fuses at the rear, so don’t kill me if I got a year/ model mistake, but there’s not a trailer ECU that’s for sure

**101RRS** · 20th August 2021, 12:27 PM

My understanding is that it is only the D3 that has the rear towing fusebox - it is not in a D4 and you need to look at the main fusebox.

Garry

**DiscoJeffster** · 20th August 2021, 12:36 PM

Originally Posted by 101RRS

My understanding is that it is only the D3 that has the rear towing fusebox - it is not in a D4 and you need to look at the main fusebox.

Garry

Yeah. There you go

**gavinwibrow** · 20th August 2021, 01:03 PM

Originally Posted by DiscoJeffster

Yeah. There you go

Thanks guys, been through the fusebox (appears only this bottom one has any trailer related fuses), but my sparky did fit Tim's Traxide kit, so hopefully will remember if and where they added any fuses that could be relevant.

**Tombie** · 20th August 2021, 01:09 PM

I would replace all those “burnt” fuses.
Seen it before!

**gavinwibrow** · 20th August 2021, 01:41 PM

Originally Posted by Tombie

I would replace all those “burnt” fuses.
Seen it before!

Thanks again. Will do a complete changeover for "coloured blade" fuses.

Plus, have just managed to get everything working after rotating "affected" fuses and the 7 round pin to flat pin adapter is now a prime suspect and will change the trailer round pin to a 12 flat to be the same as the van, and see if that solves anything.

**veebs** · 20th August 2021, 02:24 PM

So using the terminology of your signature, I guess you're now on the path we all eventually find ourselves, and 'molesting' the rig...

**Macadamia** · 20th August 2021, 03:34 PM

I can only speak for the 5-seater poverty packed but I recall I have, what looks like, a fuse block in the passenger cubby. I'll double check it later if needed

**Tombie** · 20th August 2021, 03:56 PM

Originally Posted by Macadamia

I can only speak for the 5-seater poverty packed but I recall I have, what looks like, a fuse block in the passenger cubby. I'll double check it later if needed

D3 s had a satellite fuse box in LHR
D4 has it all up the front

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