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Joined: Oct 11 2020
Posts: 65

hey ive had this issue for a while and asked on a few forums but nobody know, the main issues are the car displays nothing at all on dash for gears but if i select hi or lo it will display hi then low then select neutral then it goes blank as a result of that the car will start in any gear but unless started in park or neutral then its in limp mode and hardly moves, also i am getting reverse light on and rear wipers if wipers selected in park, reverse, 3 and 2, the led next to selected gear is always correct and the car will hold in 1 if 1 selected same with 2 (will go from 1 to 2) and 3 (1, 2 then 3) and if in drive it will accelerate properly, reverse and kickdown work properly and park holds car and neutral it will creep depending on if on slope or not.
so the gearbox apears to be fully working but im not sure what lights and dash issue are becm or xyz or cabling

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Joined: Jan 16 2017
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Does sound like your XYZ switch is playing up, if you have access to a nanocom it will show you the various outputs from the switch, Rave will give you details of which combination will show up for each gear, I would guess you have one of the contacts not working as it should do, If its the same as the one on the Disco then if it goes into limp mode D will effectively put it in 3rd gear I think.

You might get some luck trying to take the switch apart and cleaning it with contact cleaner, when I investigated mine one of the spring contacts had gone weak and would work some times but not others. Would randomly either refuse to start, or go into limp mode when trying to drive forwards. The usual mentioned failure is down to the AC drain dripping onto the switch.

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Joined: Oct 11 2020
Posts: 65

Thing is as well the reverse lights were on all the time then it changed to above I had to have becm fixed 2 days after I got car, but there is no other problems and I'm sure there was nothing on dash before becm went away but regarding reverse light issue I've no idea if it was working before or not

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Joined: Oct 11 2020
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BrianH wrote:

Does sound like your XYZ switch is playing up, if you have access to a nanocom it will show you the various outputs from the switch, Rave will give you details of which combination will show up for each gear, I would guess you have one of the contacts not working as it should do, If its the same as the one on the Disco then if it goes into limp mode D will effectively put it in 3rd gear I think.

You might get some luck trying to take the switch apart and cleaning it with contact cleaner, when I investigated mine one of the spring contacts had gone weak and would work some times but not others. Would randomly either refuse to start, or go into limp mode when trying to drive forwards. The usual mentioned failure is down to the AC drain dripping onto the switch.

I dont know if its anything or not but I looked on rave and in the x switch row its closed in p, r, 3 and 2 which is every gear I'm getting reverse lights on and open in n, d and 1 which I'm not getting lights in

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Joined: Jan 16 2017
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The reverse light according to Rave is controlled by the becm, which will operate it based on the xyz switch outputs. if you don't have access to a Nano or other diagnostics, then you could test the switch directly with a multimeter, though I'd suspect it would be more difficult to do so. Worth noting that there is a bit of adjustment on the actual switch itself (it pivots a bit on the bolts once they are loosened) and it may need a slight adjustment to get it in the right place. Easiest to do with one person watching the dash and moving the stick, whilst the other moves the xyz switch around.

What needed fixing on the BECM though? This fault/issue or something else?

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Joined: Jan 16 2017
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If you look at the table with the outputs you mention above, it also shows pins 8 36 and 37 are the outputs from the switch. Might be worth checking those at the ecu or work out which pins they are as they exit the switch and that should prove if the switch is the problem. I'd posted the above before your reply above popped up.

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Joined: Oct 11 2020
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It went into permanent lockout and couldn't start becm went bad so was cloned to new becm and tested in test car and was all working I thought the adjustment was for led light and there always correct bud

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Joined: Jan 16 2017
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I know when I had issues on mine (Granted it was a D2 rather than P38 but has a very similar switch and issues) it only had to see the switches change in the wrong sequence to upset it, You could watch it do it with the nano in front of you, two of the swtiches would go across every time, the 3rd would work most of the time and then fail occasionally to do it when it should, then would drop a second or two later. That would be long enough to get a flashing gear display though did keep the led on the stick lit once it would get the expected input the gear display would keep flashing all the same.

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Joined: Oct 11 2020
Posts: 65

The computers and electronic side doesn't seem to have been designed by anyone with a clue about computers and cars working in harmony everything is arse about tit, that I discovered getting keyless entry and push start tapped into becm lol

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Joined: Dec 30 2015
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If the LED next to the gearlever is correct, that suggests the XYZ switch is OK as it drives them as well as supplying data to the BeCM to display the selected gear on the dash. Could be that the X line is grounded somewhere between the splice (S610) and the BeCM pin 8 on C626 (Blue/Black wire).

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Gilbertd wrote:

If the LED next to the gearlever is correct, that suggests the XYZ switch is OK as it drives them as well as supplying data to the BeCM to display the selected gear on the dash. Could be that the X line is grounded somewhere between the splice (S610) and the BeCM pin 8 on C626 (Blue/Black wire).

That's lost me lol, don't know were to start looking for them

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Joined: Oct 11 2020
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C636 pin 8 front lower plug on becm facing pedals and nearest gear stick but s610 i be no idea

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Neither do I, the ETM tells you where everything is except the splices in the loom.....

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When I put the becm back in I routedcsome plugs wrong they were tight so I disconnected and re routed, I can't remember plugs but wonder if maybe I nicked cable and its maybe grounding I will have good look tomorrow

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Gilbertd wrote:

Neither do I, the ETM tells you where everything is except the splices in the loom.....

ETM??

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Electrical Troubleshooting Manual in RAVE

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Joined: Oct 11 2020
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ok things done today, i removed becm and had a look at plugs and cables as far as i could, no signs of any damage even were they go through transmission tunnel so i went underneith and all looks good under there aswell dirty, dry but looks ok, the switch is black plug with i think a clear breather pipe onto going into a black tube, i cannot see what looks like an AC drain so i was moving gear selector i noticed if i went from lo to high in low the lights all flashed 3-4 times then went solid red, there was no beeping sound and it said select neutral that disapeared but it kept low on the dash but hewn put back in high the hi stay about 10 seconds but the select neutral disapeared in about 3 seconds but after that much the same as 1st post

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AC drain is a conical rubber thing directly above the XYZ switch in the floor of the car. If your breather is still attached it won't have been water dropping into the switch though. If the BeCM is not seeing the correct gear positions it will tell you to select neutral when you try to change range as it is thinking you aren't in neutral even when you are. When you select Low, the lights next to the gearlever will flash and at the same time the range light on the dash will flash, it will beep in time with the flashing and after 3 or 4 flashes, it will select low and display that on the dash. The same should happen when you select High. So it sounds like you can select low and high ratios in the transfer case but for some reason the gear position from the gearbox isn't displaying correctly.

Do you have a multimeter and know how to use it? If you do, probe the connection at pin 8 of C626 and measure the resistance to ground. When gears where the X line should be open circuit (N and D) are selected, you should get no reading (infinity or OL depending on the meter), whenever any of the other gears are selected you should see minimal resistance to ground. If you get a reading in N or D, it is quite likely that the BeCM is seeing sufficient ground to think the switch is closed but not enough for the lights next to the gearlever to respond. I would think there is a pull up resistor in the BeCM so it detects a positive ground signal rather than a floating signal and that may be where the fault lies. In that case, I would try connecting a 10k Ohm resistor between the X line and a battery feed. That would ensure it only responds to a full ground signal and not a high resistance floating signal.

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Joined: Oct 11 2020
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it dowsnt put lights on in n or d just p, r, 3 and 2 and im wondering if i should try resistor anyway also the lights flash in low but no beeping and it says select neutral then leaves low on dash but when back in high it says high briefly then off after about 10 seconds and says select neutral about 3-4 seconfs then off

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Joined: Oct 11 2020
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so if i add a resistor would i cut the cable to the becm and connect ressitor from becm pin 8 plug to +ve or leave cable connected and tap the resistor into it