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Jaguar xkr 2012.
I previously had a rough idle with stalling due to a broken camshaft sensor I was told it was lower under thermostat housing. All been well for months
Now same again with the code camshaft sensor b bank 2 po391. Is this the same sensor I had replaced or a different one I'm struggling to find information on it.
Jaguar xkr 2012.
Now same again with the code camshaft sensor b bank 2 po391. Is this the same sensor I had replaced or a different one I'm struggling to find information on it.
P0391 occasionally popped up on my 2010 NA XK.
It is the the Exhaust Camshaft sensor on the left bank (oil filler side), "signal out of expected range". Meaning, the signals indicated the camshaft was not in the phase position expected by the ECU.
This particular sensor is hard to get to because the thermostat housing is in the way.
As there were no other symptoms I just cleared the obd code after it occurred which was about one in twenty start ups.
Earlier this year though, the coolant was drained and I had the opportunity to swap that sensor and it's corresponding solenoid with ones on the other bank. That way I could isolate the intermittent fault to either the sensor, the solenoid or the un-swapped parts (wiring or vvt mechanism).
At that point the timing chain tensioners were also upgraded and I've never had the code come up again. I'm inclined to think that a tensioner could occasionally stick (because the mechanism had worn a recess in the guide at 83,000 miles) and at cold start caused a cam mistiming signal.
If that sensor has already been replaced I suggest clearing the code and monitoring for when or if it recurs. For mine, the cause was probably the tensioner sometimes sticking whilst starting the engine before operating properly.
I would also suggest swapping the sensor and solenoids between camshafts to identify if either of those are faulty. If the fault doesn't move, it has to be a mechanical issue with the camshaft timing or loose electrical plug or wiring.
P0391 occasionally popped up on my 2010 NA XK.
It is the the Exhaust Camshaft sensor on the left bank (oil filler side), "signal out of expected range". Meaning, the signals indicated the camshaft was not in the phase position expected by the ECU.
This particular sensor is hard to get to because the thermostat housing is in the way.
As there were no other symptoms I just cleared the obd code after it occurred which was about one in twenty start ups.
Earlier this year though, the coolant was drained and I had the opportunity to swap that sensor and it's corresponding solenoid with ones on the other bank. That way I could isolate the intermittent fault to either the sensor, the solenoid or the un-swapped parts (wiring or vvt mechanism).
At that point the timing chain tensioners were also upgraded and I've never had the code come up again. I'm inclined to think that a tensioner could occasionally stick (because the mechanism had worn a recess in the guide at 83,000 miles) and at cold start caused a cam mistiming signal.
If that sensor has already been replaced I suggest clearing the code and monitoring for when or if it recurs. For mine, the cause was probably the tensioner sometimes sticking whilst starting the engine before operating properly.
I would also suggest swapping the sensor and solenoids between camshafts to identify if either of those are faulty. If the fault doesn't move, it has to be a mechanical issue with the camshaft timing or loose electrical plug or wiring.
Good luck, please let us know what's happening.
Hi thanks for the advice anything helps I'm new to the Jag world.
I have tried clearing the code as I did with the previous time it failed and it will not clear at all and the check engine light stays on. Mine occurs when driving compared to on start up and previously used to stall when coming to a stop. This time around it just bucks like a horse so until fixed is not being driven. I know the timing tensioners can be a pain on these but I have no symptoms of bad timing other than this one sensor going and it runs perfect when the new one was fitted previously. I'm more concerned weather it was just a defective part or if something else is breaking the sensor or you may be right with the solenoid perhaps
P0391 occasionally popped up on my 2010 NA XK.
It is the the Exhaust Camshaft sensor on the left bank (oil filler side), "signal out of expected range". Meaning, the signals indicated the camshaft was not in the phase position expected by the ECU.
This particular sensor is hard to get to because the thermostat housing is in the way.
As there were no other symptoms I just cleared the obd code after it occurred which was about one in twenty start ups.
Earlier this year though, the coolant was drained and I had the opportunity to swap that sensor and it's corresponding solenoid with ones on the other bank. That way I could isolate the intermittent fault to either the sensor, the solenoid or the un-swapped parts (wiring or vvt mechanism).
At that point the timing chain tensioners were also upgraded and I've never had the code come up again. I'm inclined to think that a tensioner could occasionally stick (because the mechanism had worn a recess in the guide at 83,000 miles) and at cold start caused a cam mistiming signal.
If that sensor has already been replaced I suggest clearing the code and monitoring for when or if it recurs. For mine, the cause was probably the tensioner sometimes sticking whilst starting the engine before operating properly.
I would also suggest swapping the sensor and solenoids between camshafts to identify if either of those are faulty. If the fault doesn't move, it has to be a mechanical issue with the camshaft timing or loose electrical plug or wiring.
Good luck, please let us know what's happening.
This exactly shows what comes up after clearing and won't clear
Jaguar xkr 2012.
I previously had a rough idle with stalling due to a broken camshaft sensor I was told it was lower under thermostat housing. All been well for months
Now same again with the code camshaft sensor b bank 2 po391. Is this the same sensor I had replaced or a different one I'm struggling to find information on it.
Do you have the ability to read the OBDII monitor data? With OBDFusion you can see the actual data being posted as part of the OBD monitoring cycle. That includes the data on where the camshafts are rotating to and how much of an adjustment bias is being applied. See screenshots attached. Camshaft position data from the Monitor function on OBDFusion. 2012 XK X150 NA
Last edited by DeeDoubleYou; Jul 16, 2025 at 08:34 AM.
So the fault is constant and affects running.
Swapping sensors and solenoids around with the other bank will require draining coolant and moving the thermostat housing out the way.
If the timing chain had moved a link I believe you should get other codes as well.
Electrical tests are possible backpinning by experienced person but there's risk of damaging stuff.
One straight forward test, I'm thinking would be to unplug all four camshaft sensors and all four solenoids and check it starts and idles smoothly. From experience with the NA, the CEL will come on and with restricted performance message. The camshafts should all be locked in their base position and the engine should run smoothly.
If its running smoothly then you definitely have an electrical fault (solenoid/sensor/wiring/ECU). My next step would be to swap around the sensors and solenoids so you know you have good devices in the left bank exhaust position. Then see if the fault moves to a different camshaft.
If it still runs badly with the vvt controls disconnected, I don't know. Could it be the vvt mechanism has jammed in a retarded position? The exhaust base position is advanced with the valves closing before piston tdc at idle speeds so that would mess with the tick over. Just a theory.
Do you have the ability to read the OBDII monitor data? With OBDFusion you can see the actual data being posted as part of the OBD monitoring cycle. That includes the data on where the camshafts are rotating to and how much of an adjustment bias is being applied. See screenshots attached. Camshaft position data from the Monitor function on OBDFusion. 2012 XK X150 NA
I'm downloading it now I'll add pictures with what it's showing
So the fault is constant and affects running.
Swapping sensors and solenoids around with the other bank will require draining coolant and moving the thermostat housing out the way.
If the timing chain had moved a link I believe you should get other codes as well.
Electrical tests are possible backpinning by experienced person but there's risk of damaging stuff.
One straight forward test, I'm thinking would be to unplug all four camshaft sensors and all four solenoids and check it starts and idles smoothly. From experience with the NA, the CEL will come on and with restricted performance message. The camshafts should all be locked in their base position and the engine should run smoothly.
If its running smoothly then you definitely have an electrical fault (solenoid/sensor/wiring/ECU). My next step would be to swap around the sensors and solenoids so you know you have good devices in the left bank exhaust position. Then see if the fault moves to a different camshaft.
If it still runs badly with the vvt controls disconnected, I don't know. Could it be the vvt mechanism has jammed in a retarded position? The exhaust base position is advanced with the valves closing before piston tdc at idle speeds so that would mess with the tick over. Just a theory.
Sounds like something I'll ask my mechanic to do he's pretty good so I'll get him to have a play around with it "hopefully" it is just the defective part as I've heard horror stories of piston and valve contact from mistiming but I believe you are correct with additional faults showing such as misfires and usually the crank position too
Do you have the ability to read the OBDII monitor data? With OBDFusion you can see the actual data being posted as part of the OBD monitoring cycle. That includes the data on where the camshafts are rotating to and how much of an adjustment bias is being applied. See screenshots attached. Camshaft position data from the Monitor function on OBDFusion. 2012 XK X150 NA
I mean everything is within range looks fairly similar to yours in terms of figures
I mean everything is within range looks fairly similar to yours in terms of figures
I'd forgotten about fusion, despite using it myself before....Duh.
It's a great test and those figures are much the same as ones I've recorded, and, as you say, they are healthy (at idle) vvt figures.
The fact that you are obtaining $A5 and $A6 data indicates your exhaust camshaft sensor is functioning.
So why P0391?
Maybe the camshaft is not phasing when it should..
Did you see the data change as the camshaft angles change at higher rpm?
I think ,$A5 should reduce from 120 to a minimum of 70 as the exhaust phase retards up to 50 degrees. I've not tried reading the timing at higher revs with fusion but when I used icarsoft I saw the data waveform change (but Icarsoft is no good for actual data values).
Excellent idea. I'd forgotten about fusion despite using once myself to check valve timing .
That you have $A5 data indicates the sensor is working.
Do the values change at higher rpm?, they should reduce from 119 to as low as 70 as the cam phase retards by upto 50 degrees.
I've only checked tickover values myself with fusion so don't know for sure but I did see the $A5 waveform change on an Icarsoft reader (but that device is unable to provide actual values).
If the value stays at 119 (and the corresponding bank 1 value changes) I'd check out the solonoid next.
I'd forgotten about fusion, despite using it myself before....Duh.
It's a great test and those figures are much the same as ones I've recorded, and, as you say, they are healthy (at idle) vvt figures.
The fact that you are obtaining $A5 and $A6 data indicates your exhaust camshaft sensor is functioning.
So why P0391?
Maybe the camshaft is not phasing when it should..
Did you see the data change as the camshaft angles change at higher rpm?
I think ,$A5 should reduce from 120 to a minimum of 70 as the exhaust phase retards up to 50 degrees. I've not tried reading the timing at higher revs with fusion but when I used icarsoft I saw the data waveform change (but Icarsoft is no good for actual data values).
Incidentally, whats the mileage?
88k
I'll have a little play around tomorrow see how the data turn out. In full honesty I'm reluctant to start or drive it due to scaring myself with other forums on here about pistons hitting valves and engines going goodbye. I'm hoping someone can reassure me that this isn't looking like that. When I took this data it was a smooth idle but soon started surging and dropping and then back to smooth.
Probably worth noting that my mechanic said something electrical isn't consistent couldn't work out if it was battery or alternator but I don't seem to get a constant voltage to anything but is still high enough to function. Not sure if this would cause issues. I did have a listen for any rattles earlier and all I could hear really was ticking from the engine .
Last edited by Jayden l33; Jul 16, 2025 at 01:33 PM.
I've read about things going weird when the battery's low, and from experience the electronics seem rather sensitive to low voltage so I got a led cigarette lighter voltmeter from eBay to keep a constant eye on vehicle voltage. Might be worth getting one so you could see if the rough running coincides with some kind of intermittent charging issue.
So since posting this I have gone and had the gearbox serviced and once again a new camshaft position sensor now with no codes and no stalling it seems to be an improvement however the engine still seems to vibrate the whole car especially on cold start and today I noticed a small intermittent rattle/clicking noise from the front end of the block. This noise after driving it to the shop and checking again was gone but I'll have another listen on the next cold start.
Excellent idea. I'd forgotten about fusion despite using once myself to check valve timing .
That you have $A5 data indicates the sensor is working.
Do the values change at higher rpm?, they should reduce from 119 to as low as 70 as the cam phase retards by upto 50 degrees.
I've only checked tickover values myself with fusion so don't know for sure but I did see the $A5 waveform change on an Icarsoft reader (but that device is unable to provide actual values).
If the value stays at 119 (and the corresponding bank 1 value changes) I'd check out the solonoid next.
Following from this I had a play around with idle compared to 3k revs and nothing changes on either bank si not quite sure really
Camshaft sensor nightmare
