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P38 won't turn over


Puffernutter
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This is a 1995 4.6HSE. As ever, whilst I'm away from home, the wife breaks it!

First call I get is that it has a flat battery. My son charges it overnight (Wednesday) however when he takes it off charge on Thursday, the displays all light up, it doesn't say it's immobilised, but it wont turn over.

Tonight I'm back home, is says "key battery low" (but I don't see that being the cause as we have immobilised and then un-immobilised the car). I've tested the supply to the starter (using a moving coil meter!) and it is getting nothing. (That was a pig of a thing to get to as well!)

So, Googling says it could be a problem between the BECM and other ECUs? However I don't have a Nanocom to be able to diagnose any further.

Help!

1. Suggestions please!

2. Is there anyone in Wiltshire/Somerset that could lend me a Nanocom that is set up for a P38?

It's in the way and I need the space for the dog van tomorrow, so it's rather urgent!

Cheers

Peter
Trowbridge, Wiltshire

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Not even sure if that part is working! I've changed the batteries (they measure at 5,93v) but the red light doesn't flash on the fob, it doesn't seem to have any effect and the display still says "key fob battery low". I have another fob (from a different P38 4.6HSE (same year as well) where the red LED does flash - could I use that to sync?

Cheers

Peter

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If anybody is listening, can I have a few views please? I've been doing research on the web and through various other forums and I wonder if anyone here can confirm or deny the following statements I have found:

1. If the "Check Engine" light is on when you turn the ignition on, the BeCM and ECUs are in sync and communicating.

2. If I hear a "click" when I turn the key to position 3, that's probably from the BeCM and suggests it is awake?

3. The warning "Low Keyfob Battery" is just that and will not prevent the engin from starting?

4. The red LED in the centre front of the top of the dash is NOT flashing and I have nothing about "engine immobilised" on the display, so it probably isn't!

Therefore it would seem most likely that the problem is from the BeCM to fusebox to the starter motor (including the starter relay) ?

Would that make sense, or have I made some fundamental errors in my understanding/reading?

Cheers

Peter

(why does is always do this when it is not under cover and it is raining!)

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Your first point of call is the RAVE. It'll tell you all about how these systems interact.

It could well be the BeCM to fusebox wire, or something in the fusebox. Start with the basics, follow the wiring diagrams.

The LED on the fob does fail from time to time.

How are you resyncing the key? Should just be holding the lock button, and locking/unlocking the car at the driver's door.

And don't forget, unless it's been explicitly turned off, there are two immobilisers: the active and passive one. The passive immobiliser needs a working keyfob to turn off.

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Good News/Bad News.

Good news - removing the relay and "hot wiring" the contacts, the starter spins.

Bad News 1 - I swapped the relay for a known good one and no change.

Bad News 2 - I am not getting the "check engine" light, so it looks like the BECM and ECUs are out of sync!

Anybody with a Nanocom within a 50 mile radius of Trowbridge that I can borrow please?

Cheers

Peter

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borrow or pick up a syncmate? or the other one has worked for me in the past open bonnet (wind windows down at front so you dont lock yourself out) then key on, key off. close drivers door take the battery neg off and wait 10 secs re-apply batt neg, lock/unlock drivers door with key open door and then press unlock on rf remote ign to pos 2 and crank within 30 secs.

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Disconnect the two battery terminals from the battery and connect them together with out any battery on the car. This has a way or resetting all the error codes. Reconnect the battery and see what happens. This often works for me. Failing that you will need to resync the key fob.

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Apparently not an unusual occurrence with a flat battery. The GEMS ECU has the code stored permanently in it. It is "learnt" by the BECM and can be lost (or corrupted) so when corrupted, there's no handshake and it wont start. All the Nanocom did was get the BECM to re-learn that code. I know there is "Sync-Mate" out there, but the Nanocom has much more functionality (more than some of the LR diagnostic software) and I need to reset the SRS light (transient fault) before the MoT and I have a second P38 that will need dome TLC after I've changed the drive plate as I understand it has some logged gearbox faults.

Cheers

Peter

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