Member Since: 21 Feb 2023
Location: Lincolnshire
Posts: 24
Clutch position sensor/switch? XY calibration problem
Hi fellow disco owners, any help on this last issue appreciated.
Been doing up my Disco 3 (2005 2.7 Manual) for the past 12 months, all jobs done, but can’t get the XY Sensor to calibrate.
Symptoms: when change gear I get the number on the dash, but takes about 2 seconds to show. Which means the Amber park brake fault, and reverse lights and PDCs don’t activate etc
Tried: the usual… XY sensor calibrations found in the forums, but makes no difference. New fluids (Gearbox, Diff, Transfer), new brake pedal switch, new battery. Just tried new dedent circlip.
Help: it could be mucky magnets or faulty XY sensor, but both these need the gearbox dropping and I’d assume I’d get no dash numbers if these are faulty, also could be clutch starting to go on the way out, but I’ve had no slipping anytime, and I’d assume the recalibrate won’t go wonky immediately, hence I’m putting a plea out for other ideas. Could it be a clutch position sensor or switch? But I can’t find anything online about replacement part numbers if so. Anything else?
Thanks everyone. Btw loving the Disco.
26th Dec 2023 6:48 pm
PROFSR G
Member Since: 06 Mar 2017
Location: Lost
Posts: 4665
What method have you been using for calibration?yµ (idµ - eAµ) ψ=mψ
26th Dec 2023 7:02 pm
oxtobyd
Member Since: 21 Feb 2023
Location: Lincolnshire
Posts: 24
Hi. The following.
- select low range
- reverse until R shows on dash, and keep going a little longer
- then drive through all gears 1 to 6, until gear shows on dash (ensuring clutch fully released)
- stop car
- ignition off
- ignition on
- select high range
Cheers
26th Dec 2023 7:19 pm
PROFSR G
Member Since: 06 Mar 2017
Location: Lost
Posts: 4665
That should work, unless the handbrake switch is at fault or the clutch is slipping. XY switch failure is not common, although a clean can sometimes help if there's an issue. It can be removed without dropping the box but it will challenge you.
You haven't mentioned fault codes, so I presume you are trying to diagnose without. Test for clutch slip by hard acceleration, particularly in third and fourth whilst watching carefully the rev counter. If the counter skips whilst the revs are building you're in for a new clutch. It only takes very slight slip (imperceptible) on these to cause an XY issue.
If you do not have diagnostics, replace the handbrake switch (cheap) as this is the most likely culprit if the clutch is OK. Other possibilities are the TCM motors, but you'll need the aid of diagnostics if they or the wiring is at fault.
Least likely is the XY sensor, but eliminate the other possibilities before you go for that!yµ (idµ - eAµ) ψ=mψ
26th Dec 2023 7:50 pm
oxtobyd
Member Since: 21 Feb 2023
Location: Lincolnshire
Posts: 24
Thx for those suggestions. I do have a code reader which pulls the usual XY sensor code, and some others, which I’d dismissed, but they may actually be relevant, I’ll scan them again tomorrow and post and see if anything obvious stands out. Meanwhile I’ll look into handbrake switch. Many thanks
26th Dec 2023 8:34 pm
oxtobyd
Member Since: 21 Feb 2023
Location: Lincolnshire
Posts: 24
PROFSR G wrote:
That should work, unless the handbrake switch is at fault or the clutch is slipping. XY switch failure is not common, although a clean can sometimes help if there's an issue. It can be removed without dropping the box but it will challenge you.
You haven't mentioned fault codes, so I presume you are trying to diagnose without. Test for clutch slip by hard acceleration, particularly in third and fourth whilst watching carefully the rev counter. If the counter skips whilst the revs are building you're in for a new clutch. It only takes very slight slip (imperceptible) on these to cause an XY issue.
If you do not have diagnostics, replace the handbrake switch (cheap) as this is the most likely culprit if the clutch is OK. Other possibilities are the TCM motors, but you'll need the aid of diagnostics if they or the wiring is at fault.
Least likely is the XY sensor, but eliminate the other possibilities before you go for that!
Just wondering… if a faulty handbrake switch. Would it still work as expected, I.e. I can engage and disengage manually, but it doesn’t auto-release as xy sensor issue not recognising which gear.
26th Dec 2023 8:44 pm
PROFSR G
Member Since: 06 Mar 2017
Location: Lost
Posts: 4665
The sensor for the handbrake release is part of the clutch master cylinder, so when you lift the clutch (in gear) this sensor signals the release. So yes, although the hand brake switch might be OK, it's cheap to replace. The clutch master cyl and the other XY related components are not!
It's always good practice not to delete the codes, having them allows you to make an "informed decision" rather than relying on guesswork! If you feel the need to delete them that's OK, so long as you record them or email them to yourself for referral later!
Try going for a drive and perform the clutch test I mentioned above, as well as checking what codes are logged then post them here.
It might not solve your problem, but if the handbrake switch is original it would be no harm to replace it now anyway!yµ (idµ - eAµ) ψ=mψ
26th Dec 2023 10:20 pm
oxtobyd
Member Since: 21 Feb 2023
Location: Lincolnshire
Posts: 24
Codes scanned. Ignoring the U faults and other unrelated ones, then the relevant ones maybe…
TCCM
- P174C Gearshift lever Y position sensor - circuit low
- P1807 Four-wheel drive high ratio - short circuit to ground (odd as high low works fine)
VDM
- C1A00 Control module
Any pointers on this?
Cheers
27th Dec 2023 11:21 am
PROFSR G
Member Since: 06 Mar 2017
Location: Lost
Posts: 4665
Seems very suspiciously like a wiring/corrosion issue perhaps. Pull out the battery and check the terminals on the TCM module, a common place for trouble if water gets in there!
Inspect the terminals carefully for "greening" clean and apply dielectric grease if you have it. If it's wet you need to check the bonnet seal. (worn?)
The ECU box door must be kept fully closed. yµ (idµ - eAµ) ψ=mψ
27th Dec 2023 5:01 pm
PROFSR G
Member Since: 06 Mar 2017
Location: Lost
Posts: 4665
Member Since: 21 Feb 2023
Location: Lincolnshire
Posts: 24
Many thanks for the suggestions re wiring around TCM, I’ll have a look
27th Dec 2023 10:38 pm
oxtobyd
Member Since: 21 Feb 2023
Location: Lincolnshire
Posts: 24
Checked TCM (plug terminals and inside it) but no corrosion, also plugs also look ok… mmmm
29th Dec 2023 3:52 pm
PROFSR G
Member Since: 06 Mar 2017
Location: Lost
Posts: 4665
Check the wiring/plugs on the transmission. You can get the XY sensor plug off if you stretch your hand up the left side of the box. Easier to do this on a lift!
If the TCM is still out you could try continuity tests between the pins and the plugs. Also, sometimes water get's inside the TCM and it needs drying out, but if it was dry in the EBox this is probably not relevant.yµ (idµ - eAµ) ψ=mψ
29th Dec 2023 4:03 pm
oxtobyd
Member Since: 21 Feb 2023
Location: Lincolnshire
Posts: 24
That’s a good idea. I know when I got the Disco I could see some burn marks on the battery cover and the historical paperwork showed a new engine wiring loom, so I do wonder if the gearbox loom also got damaged but never replaced, and would maybe account for the two odd errors. Maybe for the price of a used loom. I swap it out? (Easy to do I wonder?)
30th Dec 2023 9:23 pm
PROFSR G
Member Since: 06 Mar 2017
Location: Lost
Posts: 4665
Possibly there's a historical issue there so, but one other thing I forgot to mention earlier was the earth strap from the transfer box to the body. Often they appear fine, but if you give them a good tug they can crumble or just snap if they're corroded.
As for the loom it travels along the left side of the transmission and up the back of the engine behind the crossover pipe. If I recall correctly it's clamped to the turbo scavenge pipe from the crank case breather. From there it travels to the two locking junctions on the lip of the scuttle panel. And from there to the E box.
If you search for timing belts replacement, or body removal there should be some pics, but it's easy stuff really and nothing that I think would challenge you.
You might have enough loom on the box once disconnected and unclamped to pull it up to the engine bay without the need to bring it under the crossover pipe!! That hopefully would mean you'd have the plugs and the ECU pins in front of you for the tests!
That said, it is very worthwhile to investigate the earths as these will cause a lot of trouble if compromised! If the earths are OK, and the wiring checks out OK, then you'd have to conclude it's a TCM and or XY sensor problem?yµ (idµ - eAµ) ψ=mψ
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