Gearbox Overheat (again!)

P38_OTMS · Nov 4, 2018

I know this has been covered over and over again but no-one seems to have my specific issue.

Ever since I’ve had the car the gearbox overheat warning comes on as soon as the key is turned in the ignition - therefore clearly isn’t overheating.

I’ve changed the sensor, no change. Checked the wiring, all seems ok.

Brand new battery too so it’s not the weird low battery fault.

Just wondering if I need to do some sort of electronic reset to make the message go away? Or have I got two duff sensors?

Thanks!

James

Datatek · Nov 4, 2018

P38_OTMS said:
I know this has been covered over and over again but no-one seems to have my specific issue.

Ever since I’ve had the car the gearbox overheat warning comes on as soon as the key is turned in the ignition - therefore clearly isn’t overheating.

I’ve changed the sensor, no change. Checked the wiring, all seems ok.

Brand new battery too so it’s not the weird low battery fault.

Just wondering if I need to do some sort of electronic reset to make the message go away? Or have I got two duff sensors?

Thanks!

James

Corroded connections or two duff sensors.
Diagnostics would tell you the state of the sensor, ie closed or open.

P38_OTMS · Nov 4, 2018

I’ve just blasted the connections with contact cleaner so looks like two duff sensors...

There’s no fuse or relay or anything relating to it? Assume not but if you don’t ask...

Datatek · Nov 4, 2018

P38_OTMS said:
I’ve just blasted the connections with contact cleaner so looks like two duff sensors...

There’s no fuse or relay or anything relating to it? Assume not but if you don’t ask...

I'd have to look at RAVE for the wiring diagram. Blasting contacts with contact cleaner is often not enough to remove heavy corrosion, abrasion may be needed. The sensor can be tested with a DVM.

P38_OTMS · Nov 4, 2018

Contacts on the male end of both sensors look fine, and from what I can see the female end looks ok also.

I’ll try testing the sensors

wammers · Nov 4, 2018

Sensor is normally open. Continuity check sensor.

P38_OTMS · Nov 4, 2018

Yea haven’t got contiuity on my DVM. Will see if I can borrow one locally

P38_OTMS · Nov 4, 2018

Just tested it with resistance on the multimeter and it appears both sensors are open circuit.

I really don’t fancy chasing wiring all through the car... hopefully it’s the plug

wammers · Nov 4, 2018

P38_OTMS said:
Just tested it with resistance on the multimeter and it appears both sensors are open circuit.

I really don’t fancy chasing wiring all through the car... hopefully it’s the plug

Check for short to ground Black/purple wire on plug.

pwood999 · May 29, 2019

Also got problem with sensor on my transmission cooler. In my case the wire seems intermittent where it enters the sensor plastic body. I can trigger the dash warning just by wiggling the wires.

Bigger issue is one screw has snapped off, and the other will not turn. Squirted it with plus-gas and waiting for rain to stop so I can try again. Cooler looks like there just enough space on either side of the frame to carefully drill two new pilot holes for replacement sensor screws.

Datatek · May 29, 2019

P38_OTMS said:
Yea haven’t got contiuity on my DVM. Will see if I can borrow one locally

Not got Ohms? Very unusual.

Bix · May 29, 2019

So if you have the plug disconnected it flags up overheat, if you bridge the connectors on the plug does it still flag up overheat?

ukadamwest · May 29, 2019

where in Surrey are you James.

I have a spare sensor from my oil cooler that I just replaced and is known good

pwood999 · May 29, 2019

Sensor unplug immediately triggers warning message, and also shows in Nanocom BECM Inputs as expected.
DVM measure across sensor wires shows 0.4 ohms (meter reads same with probes shorted) when sensor working. Wiggling wires sends DVM reading to >> MegOhms. Sensor wires are duff, so gonna replace.
Cooler input & outputs measure approx 50degC & 35degC after 10 minute drive, so fluid not overheating.

As above my issue is now the sensor screws !!

Grrrrrr · May 29, 2019

pwood999 said:
Also got problem with sensor on my transmission cooler. In my case the wire seems intermittent where it enters the sensor plastic body. I can trigger the dash warning just by wiggling the wires.

Bigger issue is one screw has snapped off, and the other will not turn. Squirted it with plus-gas and waiting for rain to stop so I can try again. Cooler looks like there just enough space on either side of the frame to carefully drill two new pilot holes for replacement sensor screws.

View attachment 179356

Oddly enough I think I saw the same thing on @MrGorsky 's 4.6.

Gearbox Overheat (again!)

P38_OTMS

Member

Datatek

Well-Known Member

P38_OTMS

Member

Datatek

Well-Known Member

P38_OTMS

Member

wammers

No longer with us, RIP

P38_OTMS

Member

P38_OTMS

Member

wammers

No longer with us, RIP

pwood999

Well-Known Member

Datatek

Well-Known Member

Bix

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ukadamwest

Well-Known Member

pwood999

Well-Known Member

Grrrrrr

Technician, Bodgit & Scarper Ltd

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