Hello Jag Folks,
Spend most time on Saloons forum about my older cars. 2000 S
Type never let me down till now:
Left running lights show failure.
All bulbs good and switched left to right to prove it.
Temperature sensors/diodes (91 AG 10374 BA) both good as proven
right to left.
Don’t see a bad fuse but haven’t yet figured which to check?!
Grounding left light carrier frame near individual bulbs makes
them light up.
Break lights work fine.
Turn signals work fine.
Problem is only on the left and only the running lights when
headlamps are on.
HELP Please.
ILOB–
Iain Buxton, Reno, NV 66 3.8 S-Type 61 Mark IX 2000 S-Type
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In reply to a message from ILOB Reno sent Sat 27 Aug 2016:
The fuse is #3 in the trunk fuse box. There is also a diode
in the circuit, probably in the same fuse box or somewhere
around the rear electronic control module.
Better unplug the cable on your taillight module before
pulling it out. It can be accidentally grounded as you do
and blow a fuse.–
XK120 FHC, Mark V saloon, XJ12L Series II, S-Type 3.0
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In reply to a message from Rob Reilly sent Sun 28 Aug 2016:
Rob,
Thank you for replying. All fuses in the box in the boot are
good! There are two temperature sensitive diodes (I think that’s
what they are?) one for each side and they check out fine. If
there is another one or if the ones I checked are not what you are
referring to, then I’m at a loss as to where it is located!–
The original message included these comments:
The fuse is #3 in the trunk fuse box. There is also a diode
in the circuit, probably in the same fuse box or somewhere
around the rear electronic control module.
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I was away from home when you first posted and didn’t have access to the
documentation. Just to be clear, I’m assuming that what you refer to as
running lights are the same as Jaguar call marker lights. I’m also assuming
that the LH light is not on when it should be. Is that right?
You’ve checked Rob’s suggestion of the fuse but you say that if you ground
the bulb at the holder it lights so it’s getting a supply. As you’ve already
swapped the diodes (I’m not sure they are anything to do with temperature
but you’ve swapped them anyway so it’s not the diode). You could further
check by grounding the + end of the diode which should light the lamp.
If that is the case, the problem has to be either in the Rear Electronic
Control Module or more likely, the wiring to it. The feed to the left marker
light comes from pin 6 of connector CA100 on the RECM. It should be a black
wire with a white trace. CA100 is the small one in the row of four and pin 6
is top row extreme right. To help identify pin 6, pins 2, 3 &4 in this row
are not connected and pin 5 has a black wire with a green trace. The RECM is
located behind the trim on the right hand side of the boot. If you remove
the trim the module is mounted on the inside of metal plate that has rather
larger number of bolts than necessary to retain it. If it were me, I would
disconnect this plug and then ground pin 6 of it. If the lamp lights the
trouble is probably in the module. If it doesn’t, you’ll have to check back
the wiring and look for a break.
Hello Jag Folks,
Spend most time on Saloons forum about my older cars. 2000 S Type never let
me down till now:
Left running lights show failure.
All bulbs good and switched left to right to prove it.
Temperature sensors/diodes (91 AG 10374 BA) both good as proven right to
left.
Don’t see a bad fuse but haven’t yet figured which to check?!
Grounding left light carrier frame near individual bulbs makes them light
up.
Break lights work fine.
Turn signals work fine.
Problem is only on the left and only the running lights when headlamps are
on.
HELP Please.
ILOB
Iain Buxton, Reno, NV 66 3.8 S-Type 61 Mark IX 2000 S-Type --Posted using
Jag-lovers JagFORUM [forums.jag-lovers.org]–
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting
services and resources including Photo Albums, Event Diary / Calendar, On
Line Books and more !
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In reply to a message from Eric Capron sent Sat 3 Sep 2016:
Eric,
Excited to have your reply. To clarify, when the head lamps are
on, the left rear tail lamps light on the right but not the left.
The side body marker does light.
Sorry if I miss led you.
Would love to have your assistance further.
The units I was referring to as diodes were wrapped in foam and
bound with electrical tape with the wiring on the left. I
switched them on of another and the fail is always in the left so
I eliminated that as the fault.
ILOB–
Iain Buxton, Reno, NV 66 3.8 S-Type 61 Mark IX 2000 S-Type
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My fault, I did not read your heading properly but now understand the issue.
The approach is pretty much the same but the detail is different. Fuse #3
that Rob mentioned provides a feed of 12 volts and the tail lamps light up
when a ground is provided by the RECM to that circuit. So to track down
where the fault lies you can work back from the lamp holder towards the RECM
applying a temporary ground at various points you can access. You could
start at the diode grounding first the end connected to the lamp. This
should be a black wire with a white tracer. If the lamp lights at that point
move to the other side of the diode (black with yellow trace) and since you
have already checked the diode by substitution the lamp should also light.
The next point is where the feed comes from the RECM which is pin 6 of CA63.
This connector is on the side of the RECM with two connectors. It’s the
larger black one, not the grey one. Pull the connector and make sure the
pin/socket hasn’t backed out of the plug. You will have to count the pins as
there are several black wires with yellow traces. Pin 6 is on the row with 8
pins the other row has 9. If when you ground pin 6 in the plug the lamps
light the problem is likely to be in module but as I said before, it is much
more likely to be a broken wire or bad connection between the module and the
lamp. The lighting requests arrive at the RECM as SCP data but I don’t think
that will be the trouble because the RHS lights function correctly and I
doubt Jaguar went to the trouble of sending separate data for each tail
lamp.
In reply to a message from Eric Capron sent Sat 3 Sep 2016:
Eric,
Excited to have your reply. To clarify, when the head lamps are on, the
left rear tail lamps light on the right but not the left.
The side body marker does light.
Sorry if I miss led you.
Would love to have your assistance further.
The units I was referring to as diodes were wrapped in foam and bound with
electrical tape with the wiring on the left. I switched them on of another
and the fail is always in the left so I eliminated that as the fault.
ILOB
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting
services and resources including Photo Albums, Event Diary / Calendar, On
Line Books and more !
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In reply to a message from Eric Capron sent Sat 3 Sep 2016:
Eric,
Once again, thank you. I’ll get on it in the morning!
Much thanks. Not sure where this RECM is but in the boot I guess?
Best,
ILOB–
Iain Buxton, Reno, NV 66 3.8 S-Type 61 Mark IX 2000 S-Type
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In reply to a message from Eric Capron sent Sat 3 Sep 2016:
Eric,
Plug and pin checked out OK so I took the plunge and purchased a
used RECM. Iffy I suppose but cannot justify a dealer new part.
Car only has 38,000 miles but now resale value.
Is the programming an issue? I matched the numbering including
revision numbering to try to get the right match. There were
other units a bit cheaper bu the revisions were different.
Example BB or BD and Not B as in mine.
I’ll let you now if I get back on the road. Car doesn’t start
with the control unit so I will be out a while.
ILOB–
The original message included these comments:
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In reply to a message from ILOB Reno sent Sun 4 Sep 2016:
Thanks to Eric.
I ordered a replacement used rear ECU and installed it this
morning. To my great delight, everything now works as it
should!
Once again illustrating to us all how effective this forum
is.
Best,
ILOB–
The original message included these comments:
I’ll let you now if I get back on the road. Car doesn’t start
with the control unit so I will be out a while.
ILOB
Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !
Hi everyone - I read this thread with great interest.
My Jaguar S type started showing this odd behaviour with lights - lower light on just the right hand cluster. I checked fuses to no avail.
An electrician visited (before I read this thread) and advised me to buy two new light clusters. I got them and he came back. Same problem. Swapping the bulbs did the same of course!
His pronouncement then was that this was the rear ECM and I’d have to replace that, as he was convinced it was throwing out lower voltage.
So now I’ve bought a new ECM (same exact part number) and the same problem happens. This is when it dawned on me I should have asked you all earlier.
So - given I now have two sets of lights and two ECMs, can you advise me what I should test to diagnose if this is a break or grounding problem?
I have a multimeter and used to do computer cabling work - I understand electrics but may need things explaining (for example, adding a temporary ground is something I’m not sure how to do).
If you can advise me how to at least try to figure this out, I’d be delighted. It’s really getting me down this week and on top of that, the cart won’t start, the MOT is overdue and I’d like to drive it off a cliff, if I could ;-o
Any help appreciated - at least if I can prove this is a wiring issue, someone else can then trace that. I just feel rather stuck and need to get this sorted quickly, so I don’t have to offroad the car!
We need a bit more information. Firstly, what is the model year of your car and is it six or eight cylinder? The MY is important because the wiring changed during production. Also, is it just the rear lights that are affected? Do you mean the brake lights or the rear running lights and is it correct that all lights at the front are OK? What is the nature of the problem exactly, are they dim, out or intermittent? Am away at present so don’t have access to all my information but will try to help.
More info here - it’s a 2005 V6 2.5 Petrol Automatic.
It’s just the right hand rear cluster. The brake light and running lights are both lit but they look dimmer than the other light cluster. Indicator lights work fine.
When I depress the brake, the two big red lights (running and brake) go completely off on the right hand cluster. The small red light strangely enough, on the right hand cluster, then comes on (I’m not sure what that small red bulb is but it’s the one farthest away from the outside of the car).
So - I’ve tried a separate light cluster - and exactly the same behaviour. I’ve swapped all the lights from the other side (which work) and the problem is the same. I’ve tried a new rear ECM.
It’s just really odd that they are lit, but dimmer.
I have a multimeter I can try - it has clips and probes, so happy to do any checks you advise. Could this be a short or grounding problem?
It’s helpful to understand a bit about how the system works. The RECM does not supply volts, it creates a ground when required. If there is a call for lighting either because you switched the lights on or that they came on automatically a 12 volt supply is applied to the lamps. The particular supply is shared between the stop light bulb, the two tail light bulbs in the cluster and the rear fog light. It’s one supply on each side of the car that is common to all those.
When you switch the lights on the signal is sent to the instrument cluster where it is coded into a data stream and then sent around the car where it’s needed. For the rear lights, the data goes to the RECM where it is decoded. Depending on which lights you want on, the RECM switches an appropriate path to ground and the required bulb lights up because it already has the 12 volts and now it has a ground so it comes on or should do. I do not think there is anything wrong with the data for two reasons. Firstly, although a different part of the data word the same stream carries the information for the LHS and that is working. Also, the brake switch operates directly on the RECM and no data is involved but that also doesn’t work properly.
I can see why your mechanic accused the RECM but there are some tests that should have been done first and anyway, you’ve changed it no and it’s made no difference. (Sorry, I’m not intending to be rude but I am assuming that you found the right module as there are a lot around the boot. It’s the one hidden behind a metal plate on the right side behind some trim and it has four connectors on one side and one on the other).
So, what to do? Well first you need to check the 12 volt supply to the bulb cluster and compare your reading with the working side. On both sides it is the brown wire with the green tracer. Get one lead of your meter clipped to a good earth point it the boot somewhere and with the lights on and the fault exhibited take a note of the reading on the good side and then the faulty side and compare them. If the RHS is significantly lower that the LHS reading, say 1 volt or more you have at least started to find the root cause. There may not be that much difference but you should get almost identical readings. Also try with someone pressing the brake pedal and see what you get.
If the readings are pretty much the same side to side then the next most likely culprit is a poor earth connection. The RECM for your model has five separate earth or ground wires. They are all black but the come from two different connectors. One of the connectors is the only white one and the other is the black one next to the small connector (ie not the one next to the white connector). Inspect these carefully for corrosion on the pin mating side. The five black wires are all hanked to together and are grounded at a single point on the RHS of the boot. Have a very good look at this point and the way that the wires are electrically connected here ie no damage or corrosion.
Let me know how you get on with this and then we can see if more detective work is needed. By the way, if you can follow an electrical wiring diagram locate a copy of the Electrical Guide for your model year. They are readily available and invaluable in sorting this type of problem out.
Thank you Eric - that does indeed give me everything I need to know.
Thanks for explaining it. I managed to get the electrical diagrams so that’s sorted.
I did get the correct rear ECM - same serial/revision run (very handy that it’s behind another one ECM haha)
It’s interesting that the new unit fails but it may also have the same fault. That’s why I don’t think the electric guy did the right diagnosis, as you suggested - because he hasn’t isolated the fault.
I suspect the problem is most likely wiring/corrosion after reading your note - so will go and do some checking.
Do I need to use a designated earth point for the meter or will clipping it to a bit of the chassis work?
I’ll let you know what happens when I check the voltage later today…
Any sound earthing point will do just fine. It is not impossible that your replacement RECM has the same fault but I do think rather improbable. If you don’t find the voltage low (less likely) or an earthing fault (more likely) then the next stage would be to prove out the wiring which you can do by unplugging connector CA63 and after checking that you still have the 12 volts at the lamp assembly, very carefully putting a temporary earth on the pin going to each bulb. You can see which pins now you have the diagram. If each lamp lights to full brightness that rules out the wiring between the RECM and the lamps. That only leaves the module itself and the wiring to ground.
Great - that gives me the next step. Strangely enough, I also have two light clusters now after the electrician originally thought they were at fault. I swapped a new cluster in and the same problem - I’ll still follow your diagnostic path though, as I want to be sure, unlike the guy who pretended to be an electrician!
I grounded the meter to the earthing point and recorded:
Without brake:
RHS = 15.3mV
LHS = 13.22V
With brake:
RHS = 12.9mV
LHS = 13.22V
So the voltage looks pretty constant to the brown wire with green stripe on the left hand side but not the right hand side. That voltage looks really low - I hope I have the correct wire as the left and right wiring seems different…
The low voltage on the right might explain why that unit is so dim. Anything I can do to double check I have the right wire or that the voltage I’m seeing is what is going to the lights - for example, measuring the voltage at the bulb holder?
So - what would the next step be after that, assuming the voltage to the light cluster is the problem - checking the RECM output?
Thanks for all your help. I just noticed the tail light (the little strip of LEDs on the window - has now gone out too) - so I’ll check that as well!
So - it turned out to be one of those dual fault things.
When I first started looking at this, the light cluster was obviously faulty - because I can show the new one I have works fine. I didn’t know that at the time and I think what then happened was that the fuse failed.
I had noticed the tail (long LED strip) in the middle of the window (which had been working) was now off during braking. I also had a problem with the car starting. Hmmmmm.
So after a bit of faffing around, I know the following - the new ECM causes the car to not kick over and start - it just turns, catches a bit and then that’s it. Putting the old ECM back in cures that one.
I then checked the fuses and Fuse F53 in the boot fuse compartment (tail stop light) had failed. Replaced that with the spare and with the new light cluster, it works perfectly.
I guess I’d have had a simpler time if the fuse hadn’t been busted whilst all this was going on - I just didn’t notice! It’s really odd that with the fuse out, there’s still a trickle of voltage to the right hand light cluster. Once the fuse is in, the lights - tail, stop, everything work perfectly and symmetrically!
So now the car is actually running, the lights working - I can now get an MOT. Odd that the electrician who looked at it didn’t spot anything untoward but after a bit of head scratching and luck, I’m there.
Thank you Eric - I really appreciate your knowledge and always value both receiving and giving knowledge freely. It’s a wonderful thing and you’ve been an amazing help to me and others, so cheers from me!
That’s great news, Craig. Very pleased to hear that it’s sorted. Interesting that the car won’t run with the replacement RECM. I know the early model RECMs are not coded in a way that prevents the car running. Maybe that changed with the facelift but that’s no more than a theory.
Anyway, you’re up and running and now able to enjoy your car. I think they’re great cars and terrific value for money.
