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Gonk

Member Since: 18 Aug 2024
Location: Baldivis, WA
Posts: 2

Possible ECU failure

Hi Folks. I joined just now and have a question already.

Please direct me to the right place if this has been discussed already. Otherwise, pull up a chair, make yourself a cuppa, and settle in. This is a good one.

I have a starting problem.

I have a 2013 Defender Puma 2.2 with dual batteries, 1 starter and 1 aux.

I let the battery run down flat, car wouldn't start emitting that clicking noise suggesting a flat battery.
I took out both batteries and charged the starter battery. Aux battery is charged while the engine is running and doesn't affect ignition.
After charging the starter battery, I installed it, tried starting the engine, which turned over and started then immediately stopped. Tried again, same thing.
I thought it was the immobiliser as the red light was still lit on the dash. Pressed unlock on the remote key fob, and nothing. No door locks moving, no indicator lights flashing. Tried the other key fob. Nothing.
Also, I noticed that the alarm did not go off when I opened the door.

Checked all the fuses - all good and secure.
Checked relays - all secure

I did some research, and found a way to start. I have to turn key and try and start, remove key, remove a 30A fuse from under driver's seat, turn key and try to start again, remove key, then re-insert fuse, and car will start and behave normally.
I'm sure this way of starting is not ideal.
I changed the batteries in both remotes while I was sitting in the car as per driver's manual procedure.

I suspect that the ECU has lost sync with the remotes, so I took it to a place that could reset and sync ECU and remotes.

They plugged in their diagnostic tool and told me that there was an error, "No Communication" with the ECU.

Now I don't want to go and shell out for a new ECU if possible, so does anyone have any suggestions?

Here's hoping it's a simple fix, but as a relatively new Defender owner, I doubt it!

Im no auto sparky, but I have good mechanical skills.

Please help!!

Gonk

18th Aug 2024 7:47am

andy63

Member Since: 30 Jun 2023
Location: north east
Posts: 409

I have some experience with the ford twin battery set up in the ford transit..it may be similar..
What I remember is that it's a great set up, but the aux or second battery pretty well takes care of most of the vehicle systems and if that is not well charged it can cause all manner of strange behaviour..so the first thing I'd make sure of is that your aux battery is in fact in good condition..ie charged and still has good capacity as that's what is likely running the alarm central locking and everything else that consumes power when the engine isn't running..
On the transits I think the first indication of a failing aux battery was strange behaviour of the remote fob..

19th Aug 2024 8:34pm

s55shh

Member Since: 30 Dec 2019
Location: staffs
Posts: 192

my ECU was spiked when it went flat in bodyshop. Obviously they claimed it was nothing to do with them jump starting it. I ended up having the ECU recoded so it would work but without remote locking and used cat 1 alarm to do the central locking instead

19th Aug 2024 8:54pm

Gonk

Member Since: 18 Aug 2024
Location: Baldivis, WA
Posts: 2

The aux battery charges when the engine is running. It's mostly on 100%, maybe drops a percent when I leave it overnight.

It's a bit of a ball ache. I should have taken a photo of the setup before I took the battery out.
I'll try swapping some of the same colour leads around from aux to main battery. It seems coincidental that this started happening after I re-installed batteries.

One of the positive leads does get quite hot when the aux battery is charging, cools down when on 100%. Lead has an in-line fuse, so hoping it will blow before lead melts, unless fuse it too high.

Also, I have a compressor under the driver's seat which also stopped working on battery re-installation.

At a stretch, I could find out where the dual battery set-up was originally done and take it back there if not too far away.

Thanks for your input. It gives me food for thought.

20th Aug 2024 1:48pm

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