I was picking my mum up from the train station yesterday and on the way back after i'd gone round a roundabout, the car wouldn't upshift from 2nd. I was doing just over 3000rpm at 30mph and couldn't change up. I switched it to manual and tried but it wouldn't have it. 3rd lit up but immediately switched to 2 instead with no gear change. I had 4 miles to go with a line of traffic behind so was a bit of a nightmare. I dropped my mum off, turned the car off and on and that seem to fix it until i lifted my foot off to slow down for a roundabout. It seemed like there was a bit much engine braking going on then when i left the roundabout it wouldn't upshift again from 2 so I limped home stopping and starting a couple of times.

I googled the symptoms and the internet says that the TCM might be going into cooling strategy? Usual cause is blocked bottom of the radiator. My radiator is only 4 months old as i had coolant leaks so changed the Rad, thermostat and oil cooler thermostat and acouple of hoses. So i'm not convinced it's that.

I stuck the computer on it and i got DTC 85 - TCM, CAN bus missing nodes detected - Intermittent.

I cleared the fault and went for a drive with no issues. I used auto, sport, manual and low range with no problems shifting.

There were no fault messages on the dash and i've got no noises to suggest anything is broken.

Does anyone have an opinion for further diagnosis? Based on the fault code and lack of audible destruction noises i'm inclined to think it's an electronic fault.

Thanks

Sometimes faults just appear if you've cleared the fault which you said was intermittent and everything is okay then don't worry to much
A host of things can throw up faults rain ice cold starting undercharged battery because the FF uses a lot of electronic/electrical circuits very minor interruptions can cause "ghost" faults to appear at least that's what I think

Could the XYZ switch cause this problem?

ta for the replies.

I doubt the XYZ as once drive is selected, the XYZ's job is done. The fault occured whilst in Drive and not touching the shifter. Could've just been one of them things that will never occur again. Lucky i have diagnostics to clear the code tho or i'd still be stuck.

My XYZ switch caused an intermittent fault - sometimes whilst driving the car would go into limp home mode - I believe the switch moves with each gear change?

Didn't know that. Maybe someone can confirm its operation.

The fault happened again yesterday.

I was out and didn't have my computer at the time but i do have an elm bluetoth OBD which i can use with torque. Limited but better than nothing. I noticed that the coolant temperature was 84 at the time of the fault and it wouldn't get over 90. Usually the car runs at around 102. I'd been driving for a good 45 minutes so engine should have been at normal running temp.

Today, no problems and car is back running at 102-105.

Gearbox fluid level is good. I decided to do a fluid change this week on the off chance that it had never been done and it somehow might have been related to the current issue. Got 4 litres out and got 6 back in. Obviously not a fluid issue as the fault persists.


Any ideas how low coolant temperature could stop the gearbox upshifting?

The inhibitor (or xyz or gear position) switch tells the transmission ECU where the driver has positioned the gear selector lever i.e. P, R, N or D. It doesn’t change signal unless the gear lever is physically moved. The shift cable connects the two.

I wonder if maybe your transmission fluid temperature sensor is playing up and producing false readings?

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ok thats a good place to start then and makes sense.

Thinking back to the other week, i did see an oil temperature on my diagnostics that was 130oc. Could have been that.

I suppose there's a chance that the oil cooler is blocked but i'd imagine that the fault would be occuring more often if it was. As i said, i fitted a new rad, thermostat and a Behr oil cooler thermostat about 2 months ago so im confident that there's no sludge in the bottom of my rad.

Just puzzled at the low engine coolant temperature at the time of the fault.

If it is the transmission oil temp sensor, i imagine that it's sump back off to change it??

Yes, ‘fraid so. The sensor is part of the transmission’s internal wiring loom, which isn’t cheap (around £180 from Land Rover), so you need to be sure that’s where the problem lies before thinking about replacing it. Have you any way of monitoring the live signal from the sensor through your diagnostics kit to see if it keeps spiking/fluctuating?

Phil

. Was a right mission getting the £70 worth of oil back in it!

Diagnostic i have is Delphi. I know how to do the basics but to be honest I've never been that in depth with it. I know it does live values and you can record and play them back after you've had a drive and all that jazz. I'll have a good look through it and see if i can pinpoint the transmission thermostat. With it not being dedicated to one car, it doesn't label everything properly depending on the car. Just comes up as oil thermostat. Could be engine or transmission. I'd imagine that both would be somewhere around the coolant temperature range?

Thanks Phil

Not gotten round to diagnosing yet as it's been christmas and haven't had the time.

I've also seemed to develop an intermittent snatching when downshifting from 3rd to 2nd. Doesn't happen all the time. Is this likely to be another symptom of a potential temperature sensor fault, or has Santa given me another fault?