Thread: '99 D2 Td5 Auto trans warning lamp - intermittent blink

It's quite likely that the sensor itself is faulty.

I fitted stand alone temp monitoring for the auto. I'm not even sure what temp the light is meant to come on at on the factory one, but it certainly shouldn't go on and off like that.

My money is on the temp sender in the cooler too. but it could be something else.
You said that you swapped the oil cooler, did you maintain the switch that was in the other cooler, or did you re-use the one in your original cooler?
i.e. unknown temp sender or having removed it and re-fitted could be dodgy.

I had the same issue with my Tdi years back.
I was up in the high country at the time and the trans light came on, panicked like crazy.
But, got under the car and felt both trans and transfer for any excessive heat, and while it was hot, it wasn't scolding hot!

The problem is there are two sensors. One in the auto trans cooler, the other is the transfer box sensor, and they both indicate a trans warning light.

If you're not getting any error codes, then you could disconnect each sensor one at a time and see if it happens again. I don't even know if the ecus (either BCU or ECU) will warn of trans temps).
I would disconnect the transfer sensor and if light comes on, then the auto is the problem.
That's what I had to do, as the Disco 1 doesn't do diagnostics!

The major reason in my case that the sensor was the obvious point to look into was that even when cold, the warning light would come on, before the engine had time to warm up.

IIRC, the sensor light comes on when trans or transfer reaches something like 115?C, so it will be very obvious if your mechanicals are not blistering hot, but warning light comes on.

Thank you very much Shack and Arthur.

I have been thinking about the sensor too, so good to hear your thoughts about this. I didn't use the sensor from my previous cooler - I obviously haven't looked closely enough as I'd assumed it wasn't possible to switch out the sensor from the cooler (I'll have another look at that).

No, I don't believe anything was blistering hot, but I'm thinking to see what sort of temperature reading I can get on the transmission oil pan now that I have Arthur's indication of 115 degC. (I don't know if this is off-track, but the Hawk Eye transmission menu includes an "Engine Temp" live reading - which confuses me as to why this is in the trans menu - could it be the transmission oil temp? Anyway, that reading was showing as being 93 - 96 deg C when I checked it whilst getting the blinking warning lamp).

Arthur, am I right in understanding you as saying a sender in the Transfer box and the trans oil cooler both connect to the warning lamp? I'll go over your description again, and give that a go.

Thanks very much again.

Myles

PS how do you create your signatures for your messages, please? Haven't worked that out yet.

Originally Posted by Campaspe Man

(I don't know if this is off-track, but the Hawk Eye transmission menu includes an "Engine Temp" live reading - which confuses me as to why this is in the trans menu - could it be the transmission oil temp? Anyway, that reading was showing as being 93 - 96 deg C when I checked it whilst getting the blinking warning lamp).

That will be the engine coolant temperature that is passed to the TCU via the canbus, it's used along with a software timer to prevent the auto from locking up until it is warm enough.

Nanocom reports it as well but the temp is completely wrong.

Originally Posted by Campaspe Man

......

Arthur, am I right in understanding you as saying a sender in the Transfer box and the trans oil cooler both connect to the warning lamp? I'll go over your description again, and give that a go.

Thanks very much again.

Myles

PS how do you create your signatures for your messages, please? Haven't worked that out yet.

1st point: yes. there is the sensor you already know about in the trans cooler.
There is also a sensor on the passengers side of the transfer box.
According to RAVE they're both using a black/light green wire. Both these wires end up at a 20pin orange connector on the RHS under the drivers side under dash recess.
From there, one of those Black/light green wires goes to the warning light.

Do you have a copy of RAVE?

2nd point: up at the very top RHS of the webpage you see My Profile and Settings. Hit Settings, and on the LHS column of that page under My Settings you will see the link to edit your sig.

Originally Posted by AK83

There is also a sensor on the passengers side of the transfer box.
According to RAVE they're both using a black/light green wire. Both these wires end up at a 20pin orange connector on the RHS under the drivers side under dash recess.
From there, one of those Black/light green wires goes to the warning light.

Quite a number of vehicles don't actually have the sensor (or the wiring) in the transfer case, in fact I've only seen 1 myself, so I'm not sure how many actually have them.

That's my knowledge on it anyway, I could be wrong and I just own a couple of unicorns..

Thanks Arthur and Shack.

I'll work on this today and let you know what I find -- including whether I have a sensor on my Transfer Case!

No, I don't have Rave even though I see it mentioned all the time. I think when I last tried to obtain it, the available link didn't work. Any suggestion how best to obtain it?
I do have the 3 volume LR workshop manual for D2 - a blessing and a curse.

As for Signatures, it seems that I don't yet have that option - perhaps I need to prove myself a bit more first?

Cheers, and I'm very grateful for all the help. Next up from me will be an SRS fault that has just come up...
Myles

Originally Posted by shack

Quite a number of vehicles don't actually have the sensor (or the wiring) in the transfer case, in fact I've only seen 1 myself, so I'm not sure how many actually have them.

That's my knowledge on it anyway, I could be wrong and I just own a couple of unicorns..

Just to confirm that neither my 99 nor 2004 Transfer Box's have the temp sensor -- although I see that the LR workshop manual at 41-4 indicates an "Oil temp switch - if fitted" at the location suggested by Arthur.

I've decided to swap the oil cooler temp sensors (hopefully without causing too much damage), and see whether the blink disappears.

On a test drive today I struggled to get the blinking warning lamp more than once, and when I surveyed the temperatures of the auto/engine/etc using a laser thingy, nothing seemed out of the ordinary (even allowing for some discrepancies).