P38A Stuck in low range

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JamesBB

JamesBB

Active Member
Posts
761
Location
Sandwich. Kent.
Hi All

1996 P38 auto petrol 4.6.

I used low range for the first time in maybe a year yesterday. All was ok, no selection problems and it behaved as expected.

Then when I went to move back to high range I had problems.

Moved the selector to neutral and moved to right and into high. Usual beep beep beep but it would not stop beeing and I got a select neutral message up. I was already in neutral but selector in high.
Staying in neutral and moving back to low the message goes and the beeping stops.

I tried moving back to high and the same thing. Cycled through the high gears and no different, constant beeping and select neutral and the amber gearbox light flashing with the beeps.

It seems to be happy to move in high and D, but it is definitely stuck in low range still. The only way to drive it without the beeping is to select the low range.

I have checked the forums, so is it likely to be:
  • Selector micro switches? - Does not sound too bad.
  • Neutral sensor - Need to find.
  • Ratio motor? - sounds worrying.............
There is a connector on the side of the transfer box with a couple of crimped plugs on it. I have noticed these get filthy and covered in mud and oil. Wondering if this is the most likely... Not sure if it is a temp sensor or the neutral sensor.

Any help is greatly appreciated.
Looking like I may need to go and lay in the snow underneath the car.

Cheers
James
 
Wont be neutral sensor as you would get a warning that the gearbox is not in neutral when you go to make the ratio change.

It is most likely the ratio change motor, be warned if it continues to try and change ratio, it can burn out the transfer box ECU.

Take the motor off and bench test, you will also be able manaul turn the ratio shaft to get it back to high range.
 
OK, thanks to Saint for the advice.

I have been busy on all sorts of other things so I have not managed to do anything until now.

According to Rave you just need to undo 4 bolts. However I have seen some people saying you need to take the prop and transmission lock off to get enough room.

Any help on that at all? I will try the Rave method and see how it goes

Cheers
James
 
Three bolts hold the motor on, there may be one on the electrical connector bracket. Once off you can turn the triangular shaft by hand to select high.
 

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Ok, some progress, its off, the motor spins with 12v. Tried each way.

I moved the shaft on the box, it turns freely.
Starting up with the motor connected but not fitted says select neutral and allow me to move to high range and into neutral. So selecting high range and neutral I would imagine the motor turns to the high position. I then turn the shaft until it lines up the motor to put back on? Is that all that is needed to align it? I suspect that more is needed to align things as the angle of movement is so small.

Thoughts appreciated.

If the fault is still there then I look at the ECU next step.

Cheers
 
Check the piece on the motor that connects to the gearbox shaft to make sure it's not worn or rounded, it may be rotating the motor but not the shaft fully?o_Oo_O
 
At last an update. I have been too busy to do anything more with it and had the use of the other car so it was not urgent.

So, the latest is:
I attached the motor connector but did not bolt the motor in place, just left it hanging.
With the ignition on I selected high range on the selector. No errors noted other than select neutral message, it seemed to be content it was in high. I suspect that means the potentiometer (or sensor) is working ok too.
Ignition back off and I manually selected high range on the side of the transfer box and then powered the motor with 12v to spin it to the correct position judging by eye.

Bolted it back in place and reconnected.

Starting up it said select neutral but it drives perfectly well in all gears whilst saying select neutral the entire time. However, no beeps and no errors. Transfer box gear light does not come on flashing so it seems ok in high.

Any idea on the select neutral that persists?

Still and ECU fault even though it seems to work?

Cheers again.
 
There's a trick on the fuse box on the side of the seat that puts the transfer into neutral for towing, ( if Im Right about this) possibly the fuse is in the wrong slot?? Check your seat fuse box.. just a thought.
Just re-read your post.. scrap that idea. Sorry..:oops:
 
Mark Piercy said:
There's a trick on the fuse box on the side of the seat that puts the transfer into neutral for towing, ( if Im Right about this) possibly the fuse is in the wrong slot?? Check your seat fuse box.. just a thought.
Just re-read your post.. scrap that idea. Sorry..:oops:
Click to expand...
From memory its fuse 11 and should be over 5 amp to select neutral.
 
Question is, what why would the ECU think it's in neutral (transfer box) if you can't actually select neutral from the gear lever? Only by putting a fuse in slot 11 in the seat fuse box??
:eek:
 
The ECU thinks that you are changing ratio and as such needs you to select N.

Have you tried selecting N, then changing to low and then back into high again?

It may be that the ECU still thinks a ratio change is in progress
 
Mark Piercy said:
Question is, what why would the ECU think it's in neutral (transfer box) if you can't actually select neutral from the gear lever? Only by putting a fuse in slot 11 in the seat fuse box??
:eek:
Click to expand...
Selcting Gearbox Neutral (which is what is is asking for) is different to Transfer Box neutral (which is the fuse jobby)....two totally sperate things....and is not the cause of the message.
 
Mark Piercy said:
Is there a shift sensor on the transfer box? Or is it just in the gear lever housing?
Click to expand...
The Transfer Box Shift Motor has a position pot. During ratio change, the transfer ECU gets the current drive selection info from the Gearbox ECU/XYZ Switch and if it is in a drive gear, it will put a message up saying 'Select Neutral' once Neutral has been selected and the transfer box ECU sees this, it will then change ratio.
 
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