Hello all, Long time no post.

I am needing some assistance diagnosing an issue with my Brothers 2006 Grande Punto 1.2 8v. One morning it just refused to start, not even trying to crank and displaying the "vehicle immobilised" light.

I gave it a quick inspection and found that the main 70amp Midi fuse had blown, I was able to start the engine by bypassing the fuse with a spanner so I replaced the fuse but it still wouldn't start, even with bypassing the fuse.

I tried a spare battery, no change and I added an additional earth to the geabox (the main engine earth had been replaced 2 years ago after it failed).

Now, completely randomly it will allow me to start and when it does if the engine is stone cold it will run... for about 5 miles, then it will start loosing all power for a second before coming back to life. If I am really unlucky the the immobilisor light will come on and I will be stuck on the main road constantly re-trying untill the immobilisor wants to let the car run.

Once this happens the car will not idle for more than 10 seconds, it just randomly stops. If I hold the revs higher than idle then It won't stall but it will keep loosing power momentarily.

If I watch via Multi ECU scan the battery voltage is constantly fluctuating between 11.5 and 12.5 volts but measured on the battery is a solid stable 14v. The Engine ECU logs not faults at all. The "Engine startup allowed" parameter shows "allowed" if the engine is running but doesn't show anything at all if the engine is immobilised.

If I query the ABS ECU and the Power steering ECU's I get a load of faults (I don't have the codes on me right now though) mostly relating to loss of CAN bus connectivity. The electric windows don't work and apparently stopped working around a year ago.

I believe this is indicating a faulty Body computer but I don't have my yellow ELM adapter on my to query the ECU. Can anyone recomend anything else to look at and to try. If I need to replace the ECU, what components do I specifically need?

Thanks all.

Might be worth just trying an additional earth to the BODY from the battery negative? (As well as the one you've put on the gearbox). You COULD have a BCM fault, but you have so many seemingly unrelated faults that my first thought is poor earthing. If you pull up the carpet and plastic strip near the passenger side door seal, there are a number of earthing points for the BCM and other electronics. Might be worth seeing if any of those are poor. Also, I've heard of water getting into the fuse box in the engine bay above the nearside front wheel. Might be worth taking that out and seeing if its damp inside - especially underneath where all the plugs go into it. The BCM itself is behind the glovebox, but there's a steel shield over it that is held on with shear bolts that you might need to drill out. If you're lucky, you'll be able to put a hacksaw slot in the ends and get them out with a screwdriver.

ECUs definitely don't like fluctuating voltages, they would interpret them has "moving" signals , resulting with strange behavior as You describe. Fully agree with Avocet regarding earthing; install a temporary jump wire (strong gage) directly between battery negative pole and a good CHASSIS earth to validate the theory, if ok make it permanent, and tell us if it worked...

Good luck, cheers, Bernie

Use some household earth cable .you can twist it around the current cables for support
All the info in the GP FAQs

varesecrazy said:

Use some household earth cable .you can twist it around the current cables for support
All the info in the GP FAQs

Click to expand...

Not house hold earth cable which is usually 6-8mm2 it could get too much load over heat and catch fire...

something like a decent jump lead 25mm2 would be a much safer option


also check the tiny wire from the top of the rocker box top is secure to the ecu

Andy Monty said:

Not house hold earth cable which is usually 6-8mm2 it could get too much load over heat and catch fire...

something like a decent jump lead 25mm2 would be a much safer option


also check the tiny wire from the top of the rocker box top is secure to the ecu

Click to expand...

cable was only to see if it reliably pumped fuel, cranked and started..
NOT as a permanent replacement.

Thanks everyone. I went back to see the car again last weekend. Read the codes on the Body computer too as I had the adapter on me that time and the one that sticks to mind is a "module failure" for the body computer (I will post all error codes when I get back to my laptop).

Anyway, the car only stalled out once which reading codes so I cleared them and then went for a test drive. Apart from struggeling under load it ran with no issues what so ever?? Aslo the observer voltages via multiecu scan were much more stable (13.2 to 12.9 with very little variation).

I am wondering if the alternator is causing voltage spikes and that is what caused the fuse to blow.

I will check the body earths, then I am tempted to swap out the alternator to see if that makes a difference.

For info, i did add an additional earth strap between the body and the battery during initial diagnoses and that made no difference.

In the meantime my brother is going to take the car on a 2 mile test run every day for a week and then I am going to go back and re-read the codes.

Update: Found the alternator casing split in 2 places so going to replace this before investigating the body ECU.

I had all the issues you've had and after changing the fuse box, throttle body and few other bits..... with no success. One of the fault codes was microprocessor, it turned out to be the ECU. I have RAC parts and labour and had a new ecu fitted and everything worked again. Sorry to be a bearer of bad news, but yours might not be this.

Update.

New alternator in. No change but the old one was in a rough state.

I completely removed the Body ECU and removed the casing. All looks good, no damage. On Saturday it was raining when i took a look at it and it wasn't starting at all. I was able to get a constant "Minicrypt" error from the body computer.

I am now thinking the issue is with the wiring look under the fusebox in the engine bay. When I did get it started I could kill the engine by touching the ABS ECU plug but the pins themselves are clean. Going to whip the wiring loom out at the weekend and have a closer look.

"touching the ABS plug", do you mean whiggling (shaking) the harness ??
If so You're probably disturbing some "not so good" connection from underneath the fuse box on the interconnection pannel.
I would remove the (engine bay) fuse box and check all connection going to it, if all seems ok, split the looms and chase for a dammaged wire that could either touch the chassis or lose its continuity.
I had that in the ABS loom that resulted in ABS faults and ESP not available (with of course a bunch of yellow/red warnings on the dash !)

Regards, Bernie.

If someone helped You on this forum, hit the thanks button, it costs nothing...

Bernievarian said:

"touching the ABS plug", do you mean whiggling (shaking) the harness ??
If so You're probably disturbing some "not so good" connection from underneath the fuse box on the interconnection pannel.
I would remove the (engine bay) fuse box and check all connection going to it, if all seems ok, split the looms and chase for a dammaged wire that could either touch the chassis or lose its continuity.
I had that in the ABS loom that resulted in ABS faults and ESP not available (with of course a bunch of yellow/red warnings on the dash !)

Regards, Bernie.

If someone helped You on this forum, hit the thanks button, it costs nothing...

Click to expand...

Thanks Bernie, Exactly my thoughts. Will try this at the weekend and report back.

Sorry to “bump” an old post, but was there any resolution to this?

Hi

Not sure Bernie is still with us

But @Ransoman might reply..
Its 5 years..


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