Range a rover P38 Gearbox power solenoid fault

Hi i have a P38 4.0 Gems 1996 and have a random fault in my dash which comes up generally from the start. It show gearbox fault and goes into limp mode. With my Nanocom it shows power solenoid fault which I can clear but it does come back again.
The voltage at the gearbox is showing only 9.5v!
At the same time it often has flickering rev and speedo and the ABS light comes on. Other things occur like the blower fans cutting in and out.
It sounds like an electrical issue like a faulty connection.
So far I have done the following:
New battery
New alternator
New battery leads
Replaced TCM
Checked and cleaned fuse box
Checked and cleaned all connections I can find or think off.
Transmission fluid is nice and clean. changed 12 months ago.
When the fault is not present it runs perfect in all gears.
Can anyone offer some advise as I’ve run out of ideas and it ****ing me right off now

How did you check the fusebox? Did you take it apart?

kermit_rr said:

How did you check the fusebox? Did you take it apart?

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Yes opened it all up, no burning and looked fine. Cleaned it thoroughly with contact cleaner.

V8FUG2 said:

Yes opened it all up, no burning and looked fine. Cleaned it thoroughly with contact cleaner.

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you'd need to check for cracks in the solder joints and the ribbon too

a dodgy connection/earth does sound likely.. i'm sure someone else had similar but i can't find the thread

I think there is a bug where the Nanocom reads the voltage low depending on what gearbox ECU you are using. The way to be sure is to disconnect the ECU and test the pins 1and 39 at the connector.

I had the same issue, and whilst I DID have earthing problems, my Nanocom still showed low volts at the ECU when I had 12.4 volts at the pin.... I added an extra earth lead from the battery - to the engine block, and a second + lead from the alternator + to the battery +. Even after all that re-wiring I got 14.4 volts at the pins, but the Nanocom only reported 12volts.

Regards that low voltage reading, I changed my ECU to a spare one with a different part number (cheap of eBay but still for a P38 petrol) and the Nanocom started reading the correct ECU voltage. Mine was reading 9.1 volts, and whilst it was low due to bad earths, a voltmeter showed 11.4 or something. I suspect your earths are bad too.... that's where I'd start, and I wouldn't bank on your Nanocom reading.

Here is my thread of doom..... the gearbox stuff starts around page 5!

Check the earth strap from engine to chassis, it's a common failure item. An east way to check is to take a jump lead from the engine to the battery negative. worth checking what voltage you have at the battery terminals with the engine running.
A new battery means nothing if you didn't fully charge is before fitting.

Datatek said:

Check the earth strap from engine to chassis, it's a common failure item. An east way to check is to take a jump lead from the engine to the battery negative. worth checking what voltage you have at the battery terminals with the engine running.
A new battery means nothing if you didn't fully charge is before fitting.

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Ordered some additional power wires for watching the battery to engine and also adding new positive cable to starter motor. Already has new cable from alternator to battery.
Battery was in full charge when fitted 100Ah 850cc.
Will check again after new cables fitted and also check becm connections again.
Thanks for the advice

Also check the post to which the earth strap attaches to the engine as that can be dirty/corroded. Bolt too, but to a lesser extent

V8FUG2 said:

Ordered some additional power wires for watching the battery to engine and also adding new positive cable to starter motor. Already has new cable from alternator to battery.
Battery was in full charge when fitted 100Ah 850cc.
Will check again after new cables fitted and also check becm connections again.
Thanks for the advice

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Report back when you're done. It'd be good to know if improving your earths cures the problem. I think it did for me, but I also had other stuff going on that may have clouded the issue for me!

I ran an additional earth from battery "-" to the belt tensioner bracket, and also an extra one from an earthing stud near the fusebox to the belt tensioner bracket. I was amazed by how much the voltage jumped. My original 1997 earthing wires must be well past their best.

I'm convinced the Nanocom voltage reading is a bug in the gearbox ECU software now. If you have Gearbox ECU software GS2.38. then it underreads by at least 2.5 volts.

Nanocom also gets the GEMS voltage wrong and reports 16V on both my P38 whether engine is running or not !! I asked about this on the BBS forums but never got any answer.

pwood999 said:

Nanocom also gets the GEMS voltage wrong and reports 16V on both my P38 whether engine is running or not !! I asked about this on the BBS forums but never got any answer.

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Mine also does this. I'm pretty sure I've read a technical bulletin stating this is a bug in the BECM software.

MrGorsky said:

Mine also does this. I'm pretty sure I've read a technical bulletin stating this is a bug in the BECM software.

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Never seen 16 volts using Fautmate. I cannot see how the BECM could cause such a reading.

Datatek said:

Never seen 16 volts using Fautmate. I cannot see how the BECM could cause such a reading.

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Have you tried it on a V8 Gems though?

It's the Engine ECU that is wrong.

MrGorsky said:

Have you tried it on a V8 Gems though?

It's the Engine ECU that is wrong.

View attachment 307298

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Ah, OK never even seen a V8 I'm pleased to say.

MrGorsky said:

Report back when you're done. It'd be good to know if improving your earths cures the problem. I think it did for me, but I also had other stuff going on that may have clouded the issue for me!

I ran an additional earth from battery "-" to the belt tensioner bracket, and also an extra one from an earthing stud near the fusebox to the belt tensioner bracket. I was amazed by how much the voltage jumped. My original 1997 earthing wires must be well past their best.

I'm convinced the Nanocom voltage reading is a bug in the gearbox ECU software now. If you have Gearbox ECU software GS2.38. then it underreads by at least 2.5 volts.

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Update so far. Removed BCEM and checked and cleaned all connections.
Waiting to fit new earth from battery to engine and new positive lead from alternator to starter.
Checked connections behind kick panels and the large white one was slightly corroded, cleaned it as best I could and voltage at gearbox is now 10.5 v and no issues so far.
Next step is relaxing this connector completely. Will keep you posted.

Cut and solder the connector wires behind the both kick panels one at a time. It cure's a multitude of sins on theses buses

Next update. Cut and soldered connections in footwell. Fitted new power cables on battery, alternator, starter and new earth lead. Still have the same problem with gearbox power solenoid fault and flicking rev and speedo.

I don't know what drives the rev counter on the V8, on the diesel an output from the alternator drives it. The rev counter flicking around is often a symptom of diode failure in the alternator. What voltage do you have across the battery terminals with the engine running?

Red and black to both battery terminals!?

Have you been watching @lrtime??? Red is black and plus is minus!?

Good idea to measure AC volts at the battery