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Have you tried holding the key with it's buttons facing out, flat against the facia just below where the foglight switch panel is, while holding the brake pedal and pressing start?
 

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Discussion Starter #42
@Rikajag

Firstly, where are you based? Second, let's take things back a few steps. Have you scanned the car for faults? If so please post all the DTC's. If not, please scan the car and post the DTC's.
1: Suffolk
2: I have tried since this problem arose, unable to read DTC'S is what im getting, I dont think the car is engaging ignition pos 1
 

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It does seem as if the key is only partially working given it can turn the cars lights on. I guess the question is whether any Jag key would be able to do that and the starting element is the bit that is unique to the car. Seems highly unlikely and therefore it would be right to think the key is communicating but the starting and locking features are not sensing the key as reported by the dash warning.
I believe your JAG (like mine) will have a second smaller battery and that I believe interacts with the key via central locking. Can you try disconnecting both batteries and completely disconnect the positive and negative terminal and leave for say 5 mins or so. Thence can you reconnect all terminals and see if the key is now recognised.
 

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Sounds like a can bus error . At either end of the bus is a 120ohm resistor these are fitted in one of the modules at each end, ie in two modules. Check between pins 2 and 7 on the data socket you should see 60 ohm. if you see 120 you have a connection problem between 2 of the modules or a faulty module. It is a process of elimination.
Diagnose Dan has a great video on how to test it on you tube.
 

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Discussion Starter #46
Sounds like a can bus error . At either end of the bus is a 120ohm resistor these are fitted in one of the modules at each end, ie in two modules. Check between pins 2 and 7 on the data socket you should see 60 ohm. if you see 120 you have a connection problem between 2 of the modules or a faulty module. It is a process of elimination.
Diagnose Dan has a great video on how to test it on you tube.
Don’t suppose you have a link do you?
 

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Discussion Starter #47
It does seem as if the key is only partially working given it can turn the cars lights on. I guess the question is whether any Jag key would be able to do that and the starting element is the bit that is unique to the car. Seems highly unlikely and therefore it would be right to think the key is communicating but the starting and locking features are not sensing the key as reported by the dash warning.
I believe your JAG (like mine) will have a second smaller battery and that I believe interacts with the key via central locking. Can you try disconnecting both batteries and completely disconnect the positive and negative terminal and leave for say 5 mins or so. Thence can you reconnect all terminals and see if the key is now recognised.
I’ll give it a go later Brian, thanks
 

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Was there any other symptoms before car goes like this? Specially intermittent ones?
What do you use read DTC codes?
 

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No need to disconnect both positive and negative, negative only will achieve the same result. I really think you car has lost it's key pairing :(
 

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Discussion Starter #50
Was there any other symptoms before car goes like this? Specially intermittent ones?
What do you use read DTC codes?
Only the low key fob battery warning but that had always been there, then obviously the fault leading me to change the main car battery. To read I have only got the generic obd2 scanner
 

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Discussion Starter #51
No need to disconnect both positive and negative, negative only will achieve the same result. I really think you car has lost it's key pairing :(
I’ll give it a go later along with the smaller one bud, failing that I’ve got a guy coming this evening that reckons he can reprogram the keys
 

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1: Suffolk
2: I have tried since this problem arose, unable to read DTC'S is what im getting, I dont think the car is engaging ignition pos 1
Ok, well if you get stuck I'm not too far from you. You can PM me.

EDIT:

I doubt its the keys mate as worst case it should've picked up the key when you put it to the column.
 

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Discussion Starter #53
Ok, well if you get stuck I'm not too far from you. You can PM me.
Where about s are you bud? Hopefully this auto locksmith will get the keys sorted, but afterwards I may need a little help? Thanks pal
 

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Sorry to be so to the point but my son rang from France and he has Corvid 19 so I wanted to speak to him. Just Search for Diagnose Dan and scroll through he is very informative. I thought that as the lights operate from the fob it may be the high speed bus which has gone down. The lights will probably be on the low speed bus but not sure.
If a module was going down fitting the new battery or removing the power may have triggered it to fail. The idea behind the bus is to save cabling, each module has a twisted pair of thin cables, an earth and a 12v supply. any one of the modules if failed can cause the problem. If you can test the high speed bus first or get the auto electrician to do it it could save a lot of time and money, if the bus reads fine then you can move on to other things.
 

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contacts are sound ninjag and tried both keys i have, both bringing same message on dash. Yes Brian the battery is in right way up. The key turns the lights on and off so i know theres some kind of connection??
Unless highly unlucky, I would guess that at least this should rule out the fob as being the problem. Electrical process of elimination as already suggested is probably the best way forward now, although I would be keen to get an icarsoft scanner (or similar) on it to read the actual Jaguar codes. You can get them for around £100 odd and it's worth having anyway, unless someone nearby has one they could connect?
 

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Mentioned previously and I'll mention again. Almost certainly a faulty CJB that's lost its memory on one of the two eeproms.

They have been shown to be repairable, but it's a bit of a pig to do.

Dealers and Indy's will usually replace the unit and reprogram to the keys.

I'm assuming you've checked for water ingress through the cables as mentioned half a dozen times on this thread.
 
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Unless highly unlucky, I would guess that at least this should rule out the fob as being the problem. Electrical process of elimination as already suggested is probably the best way forward now, although I would be keen to get an icarsoft scanner (or similar) on it to read the actual Jaguar codes. You can get them for around £100 odd and it's worth having anyway, unless someone nearby has one they could connect?
That's all well and good if you can get the ignition on. You won't be able to communicate with any modules if they're not powered up.

And it seems he can't get the ignition on.
 

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That's all well and good if you can get the ignition on. You won't be able to communicate with any modules if they're not powered up.

And it seems he can't get the ignition on.
Ah of course, I think this was mentioned and I missed it. Oh well, I would probably check the electrics first if easy enough to do and then move on from that.
 
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