Electrical Gremlins - 147 Sele

[Citroënbender]

My 2017 "revival" has been mostly behaving since then - last I required help was early 2018 from memory. 25000km have been added to it. Recent failures included both front strut tops collapsing (KYB brand, and I didn't studiously enough line up the top mount bracket with the fork, time and the B6s did the rest) and the lower transverse engine mount centre bolt (randomly?) dropped out, not a nice limp home! The four year old battery still tests within spec on CCA - amazing but true.

In the middle of a mild, sunny afternoon last week, the car suddenly unlocked itself, put the hazards on, and refused to stay locked with either key or remote. It still starts and drives but in a degraded manual mode. When the engine is running the high beams are on, the lighting stalk is inoperative, there are fictitious start-up error messages for brake fluid, all doors/hatch open. When I shut it down the left sidelight remains on.

As the indicators don't work, it's not really practical to drive, so I'm keen to sort it. The fault is odd, as though a ground has lifted, I have not checked integrity of C15 yet. I have checked inside the hazards/fogs/locking control panel and it's clean/undamaged. Inside of the car seems dry, except for the aftermarket Bluetooth it is unmodified. The only way I can lock the car is by using the remote and quickly taking off the negative terminal before it unlocks again.

Bazz - have you ever run into a fault like this?

[bazzbazz]

Nope.

Exorcism ?

Check the fuses on the battery fuse box, especially fusible links, then check all the connections to the Body ECU.

Have you run diagnostics on it yet?

[Citroënbender]

Nope.

Exorcism ?

Check the fuses on the battery fuse box, especially fusible links, then check all the connections to the Body ECU.

Have you run diagnostics on it yet?

Thanks Bazz,

I'll run MES over it today, and double check the fuse plate. It's encouraging that you haven't encountered this.

[Citroënbender]

The battery fuse plate is all good, C15 earth is sound, all connections to the body computer seem correctly engaged and latched.

On MES, most modules are clean or low concern. Instrument cluster no faults, so we can probably exclude it from considerations. Driver's door and rear doors modules, are free of stored faults. It says no need for a Proxi alignment:



Engine and gearbox appear - from my experience - to have just the usual faults:



I've included a few Key On, Engine Off parameters:



Finally, the recurrent fault logs from the body computer. When you clear the faults (they will all clear, albeit briefly) then cycle the ignition, this is what you get:



When you remote lock the doors and it "bounces" then re-lock and quickly disconnect the battery, these are the extra faults logged.

[bazzbazz]

I'd say you had a blown fuse somewhere.

Check fuses at the fuses box in front of the body ECU as well as the fuse box in the luggage compartment.

[Citroënbender]

Ta, that was probably my next mission (double check fusing), but I'm unaware of any fuses in the boot.

Other things I thought of - a breaking down combination switch on the lighting side, or a fault in the ignition switch.

The other wildcard that may have caused damage is from late 2016 when I hadn't tightened down the earth eyelet near the ECU and it carried enough current to key on but not to crank or start. My thought being, this may have stressed another earth infeed to the body computer.

[bazzbazz]

Sorry, was trying to answer two different issues on two different forums at the same time. Should read - main fuse box in front of battery. My bad.

[Citroënbender]

All fuses confirmed good, including the hidden set. I have to correct one detail in my first post on the problem, the left rear (tail) light comes on in sync with the left front.

I disconnected the headlight plug and the rear light remained lit - so it's not pulling a ground through the front light. I removed and checked the front right park globe - it's good.

Disconnecting the lighting switch unit makes no difference, nor does disconnecting the ignition switch. There's no sign of repair or abuse in the wiring.

[Craig_m67]

Pull the tacho, smell
Better yet, open it up and have a squiz at the board inside

(It's not hard to get out)

[Citroënbender]

Why the tachometer? I'm curious.

[bazzbazz]

I know what Craig is getting at, give it a go and see, only takes a few minutes.

However, the info about the front & rear lights is bit of a giveaway. I am assuming you mean both the left front & rear lights come on together whether they are selected or not?

If so I suspect you will have a problem with the Body ECU, take it out (It's the grey box mounted to the back of the under dash fuse box) and carefully open it up and see if you have any corrosion, moisture ingress or other obvious errors (burnt track, fused components).

The issue of the rear light coming on is a known error, usually caused by the failure of the corresponding Light Driver Chip. As you also have a host of other errors logged, all associated with the Body ECU, I'd say it's a pretty good candidate.

[Citroënbender]

Thanks. I'll have a crack in the morning, when it's both light and hopefully dry.

Yes, the lights come on without being selected.

I'm particularly baffled by this starting on a dry day when the car hadn't been used for maybe 36-48 hours.

[Citroënbender]

I popped the cluster out, do you mean to also remove the needles, dial faces, then the structure from the plastic back cover also? There is no sign of burning, no odd electrical smell.

Inside M1, I found this:



Looks like pooled water damage (oxides formed). I'm half inclined to brush it clean and see if it goes again. Any hints on the semiconductor ID - the top has two sets of letters: BE and QB (or is it CB, if it's a transistor)?

[bazzbazz]

Well at least you found the issue. It's a common problem.

Give it all a good clean with Isopropyl Alcohol and see how you go. (Available at any electronics store, Jaycar ect)

[Citroënbender]

Unfortunately, despite the thorough cleaning, no change to faults recorded prior.

It's perplexing because the fault is in the "middle" of the command chain. It's seeing most inputs, and most outputs can be commanded by actuator tests.

I watched a video or two by an English chap called Leon Stacey, he - with similar faults in a 147 Sele - transplanted three ICs from his faulty module to a donor and resolved the issue without loss of vehicle identity.