Hello everyone. I've owned a 2003 S Type 4.2 asp. for about two months now. In that period I've had the headlights and dash lights go out simultaneously a number of times while driving at night. The car continues to run and the FRONT turn indicators and hazard light continues to work. I'm (desperately) hoping these are symptoms that can point me to particular fuses or relays that should be swapped out. If there are other techniques for flushing out the problem please let me know.

 

Dash illumination and the headlights run from separate fuses and relays and also modules .
they only shear the switching combo switch or stalk to operate simultaneously .
id start by checking the battery condition , also check the boot/ trunk for water in the wheel well . and if both those are good i'd be swapping out the combo switch.

 

+1 on that. Lots of redundancy built into the lighting circuits. For most faults, such as a blown fuse or bad relay, you'd only lose one headlight, or just the dash lights, but not everything.

I bet you're losing your tail lights when this happens, too. I believe it is a regulation that the tail lights and dash lights be on the same circuit. The idea is a loss of dash lights is supposed to alert you that your tail lights are not working. It's easy enough to see when your headlights fail, but not so with the tail lights.

Wiring diagrams are here:

http://www.jagrepair.com/images/Elec...al%20Guide.pdf


Can you get the lights to fail from the comfort/safety of your driveway? It's really tough to diagnose an intermittent fault. About the only other thing I'd suggest checking is exactly which interior lights fail when the car acts up. Look at figure 09.2 in the wiring diagram above. Do you lose just the lights within the instrument cluster? Or everything in that diagram, including the window switches, steering wheel switches, etc?

 

A few more thoughts:

For the headlight switch, are you using the auto or manual feature? When the lights act up again, try switching from one mode to the other and see if that helps. Or try driving for a few weeks using the other mode, and see if the problem stays away.

If the fault only happens in auto mode, I wonder if your solar sensor is acting up. If the sensor mistakenly thinks it's daytime, the lights will turn off as designed. That's why I suggested switching modes. If going from manual to auto, that will take the solar sensor out of the circuit.

Does your high/low beam switch have the flash-to-pass feature? On my '02, if you pull the lever aft, it turns on just the high beams, but not the dash or tail lights. If your car is so equipped (I think so), make sure it works when all is good, and then try it again when the car acts up.

 

The default system response for a failed solar/daylight sensor is to keep the lights "on" for as long as "auto" is selected on the stalk control.

 

Many thanks for the input Datsports. I checked the battery connections and for moisture in the trunk and wheel well when I purchased the car– we're all good there. I'll proceed with swapping-out the headlight switch stalk, so if you have any instructions on how to do that I'd appreciate it, otherwise I'll search the forum. Many thanks once again!

 

 

Wow. Thanks!

 

High parts cost, minimal labor: https://www.jaguarforums.com/forum/s...solved-175596/

 

So. Mission NOT accomplished. :-(
The theory seemed sound that the simultaneous electrical blackout of the headlights and dash lights was coming from where the circuits "shear" at the turn signal stalk.
After trying two different stalks, I'm afraid it still wasn't able to cure the ailment.
Here's a recap of what works and what doesn't work when the dash and headlights go out, for anyone out there with a thought on this.
Your feedback is deeply appreciated.

Overview:
The dash lights and headlights go out intermittently, whether the engine is cold or hot or the temperature outside is cold or warm.
It happens without activating any switch or touching any peddle.
When the car is started and the lights are out they usually come on within a few minutes, whether I'm driving or the car has been sitting idle– for a while.
Usually, the intermittent wipers will activate a minute or two before the lights turn on.
The one light that coincides with working or not working with the headlights and dash lights is the overhead center dome light.

The electrical that doesn't work when the headlights/dash lights are out include...
• front and side right and left turn signals
• fog lights
• center dome light
• wind shield wipers
• wind shield washer fluid pump
• trunk button (dash)
• remote button to unlock the car

The electrical that works when the headlights/dash lights are out include...
• rear left and right turn signals
• rear foul weather lights
• rear brake lights
• all four electric windows
• locks can be activated from driver's door console
• sunroof
• left and right dome lights
• center rear view mirror auto button
• climate control panel
• radio
• glove box light
• gas filler cap lid
• trunk button internal
• trip button on stalk (A&B)
• dimmer switch for dash lights
• center gauge showing mileage and time etc...
(this is hoiw I can tell the dimmer switch is working)
• kilometer/miles button
• hazard button
• traction control
• parking brake signal
• front seat D&P motors
• front seat D&P memory button
• center console AC outlet
• engine temp
• fuel level
• trunk light
• rear license plate lights
• trunk button (on fob)
• remote button to lock the car

I hope the above helps solve this dilemma.
Thanks again everyone.
B.

 

sorry to hear the stalk was not the fix .
thats a shame its a nice easy and common fix .
thats a comprehensive list of items checked .
but the fact that the license plate and rear indicators work whilst the front indicators , head lights and tail lights shut off - shows that the stalk is indeed sending its request to the respective modules but only the rear electronics control module is responding at that time . bar the tail lights which would most likely be signaled by the front electronics control module .
I would now be looking at the FECM earth and all front earth points , and also check the fuse box connectors for corrosion .

 

Thank you for the comprehensive list of what does and doesn't act up at the same time. This info is very helpful.

Can you please clarify the terminology for the "center dome light" and the "left and right dome lights"? Please look at figure 09.1 here:


2003 Wiring Diagrams


For "center dome light", I think you mean the one with the "courtesy lamp switch" shown at the center of the left edge of the diagram. This light acts up with the rest of the naughty lights. It is controlled via the GECM and the Instrument Cluster.

For "left and right dome lights", I think you mean the LH and RH Map Lamps, shown at the center of the right edge of the diagram. These lights behave at all times. This is a very basic light circuit, just controlled via switches at the light assembly.

Would you say those descriptions are correct?


I got to wondering if one of the Switched System Power Relays (1-4) was at fault, but I don't think this is the case. See fig. 01.6 for the four power relays. Power to the front light clusters is split between relays 1 and 2. You mentioned the fuel door (fig 12.1 or 12.2) works normally. That rules out relays 2 and 4. The glove box light (fig 09.1) works normally, so that rules out relay 3.

So what about relay 1? A failure there would only affect half of lights up front, not all of them. The next time the lights fail, try adjusting the driver's mirror while the fault is active. If the mirror still works okay, then relay 1 should be okay.

Those four relays are energized simultaneously, so something really funky would have to be happening for a partial failure there. As long as you can confirm the driver's mirror adjustment works okay when the lights are inop, then those relays are probably okay.

One other thought is a fuse that powers the GECM. See figure 01.6, fuse F30 in the primary junction fuse box. This fuse box is somewhat hidden, just outboard of the US passenger's feet, forward of the door. Please inspect this fuse carefully for any sign of overheating on the two prongs. You may as well gamble 10 cents and replace it while you're in there.

One more inspection with this fuse. Please make a test gauge from a strip of thin metal cut to the same dimensions as the fuse prongs. Make sure the thickness is the same, don't just guess, but measure it carefully with a micrometer or calipers. (If you don't have a micrometer or calipers, I can measure one for you tonight) Insert the test gauge into each of the receptacles for F30. The receptacles should grip the test strip firmly. If loose, you've found the culprit.

There is a second fuse F20 in the same box for the GECM. I don't think this one is the culprit, as it is the logic power supply for the GECM, the RECM, and the instrument cluster. The last two seem to be working. However, it's free to check this fuse and receptacle as described above.

For all we know, there may be a common connector that has worked loose. I'll have to dig a little deeper for that.

One last thought, slightly out of order:

Next time the lights act up, please try the following:

1) Adjust driver's mirror (should be good)

2) Adjust passenger's mirror (probably dead)

3) Adjust steering column and pedals (probably dead)

4) Blow the horn (probably dead)

If those four items behave as expected, that will help isolate the fault. I'm leaning towards that fuse F30.

As previously suggested, check the connectors on the GECM, including the ground. The location can be seen on page 20 of the wiring diagrams. FH77 is the ground to inspect, see page 22 for a vague description. The easiest way to find it is probably physically follow the wire bundles from the GECM and look for a nearby ground terminal.

 

Thanks Datsports.
If you could please provide any additional advice on how to check the FECM earth and all front earth points it would be appreciated.
I'm new to this motor, and I couldn't find any other resource for instruction on the forum here or in the YouTube video library.
Also, if you could provide info (or a link to info) regarding what fuse box connectors to check (and how to check them) for corrosion it would be appreciated.
My wife's lost faith in this vehicle but I haven't yet, as long as I can solve this electrical issue without dumping tons into paying a mechanic to find the problem.
Again, many many thanks for your time and interest.
I'm very impressed with the amount of input members are willing/able to provide on this forum.
I suppose the mutual interest comes from wanting to avoid seeing another S Type go to the grave.

 

The GECM location can be seen in this training guide, page 76:

http://www.jagrepair.com/images/Auto...G%20S_Type.pdf

That guide is for '99-02 models, but I believe the location is similar on later models. Also check that "secondary junction box" connector in the same illustration. I'm not sure if any of the troublesome circuits pass through this connector, but I vaguely remember it causing trouble for somebody else.

 

your major earth points will be much the same as this 05 pic here

there is also an earth bolt on the primary/cabin fuse box here

this is the 03 module location for reference .


these pictures may be subject to right / left hand drive .
these photo's were stolen from other forums and sites .

 

If you heard a loud smacking noise last evening, that was me slapping my forehead. I had broken out the calipers and was measuring the prongs of some fuses to get the dimensions to make a test strip. That's when I realized just sacrifice a spare fuse. Cut it in half with a hacksaw or even snip it down the middle with a pair of dykes. You'd then have a test strip of the exact dimensions needed.

Don't test the receptacles with a whole fuse, as this checks both at once. It would be easy to miss if one receptacle was loose. You want to check each individually. That's why I suggested cutting a fuse in half.

 

Hello Karl and Datsports,

I want to thank you both very much for your input on how to solve this pesky electrical glitch that I’m experiencing.
Included here is a collection of answers addressing the combination of questions you've asked, along with a recap of the additional steps you've both suggested I take.

Answers to your previous questions:
• Datsports, I did have the battery tested as suggested— it tested fine.
• Datsports, the electrical outage happens whether the headlight and/or wiper switch is in the auto or manual mode.
The flash-to-pass function works normally when all is fine, but is out when the headlights and dash lights are out.
• Karl, I was referring to the courtesy map switch and the left and right dome lights.
The dome lights continue to work when the dash and headlights are out but the center courtesy map light switch does not.
Whenever I’m running the car during the day I leave the courtesy map switch tuned on as a way of knowing if my front turn signals are working— or not in the interest of safety.
• Karl, when the electrical is out the driver’s mirror does work but the passenger mirror does not so relay 1 should be OK (along with 2, 3 and 4), according to your previous comments.
The steering column switch will adjust the steering column up and down and in and out position but not the pedal position.
The horn does not work.

Steps to be taken:
• Look at the FECM, also referred to as the GECM in some Jaguar docs. (it took more then a few minutes to sort that one out)
- Check the ground on the FECM (FH77) and all front earth points, and also check the fuse box connectors for corrosion.
- I’ll follow the wire bundles from the GECM to find the nearby ground terminal.
- I’ll allso check that "secondary junction box" connector in the same illustration.

Thanks again Gentlemen. I'll keep you posted on how it goes.
Brian









• Inspect fuse F30 in the primary junction fuse box (figure 01.6), which powers the GECM, just outboard of the US passenger's feet.
• Insert a test gauge into each of the receptacles for F30. The receptacles should grip the test strip firmly. If loose, we've found the culprit.
(Karl, I read your recent post about making the test strip from a spare fuse— point taken. Thanks)
• Inspect fuse F30 as noted above.
• Check the earth bolt on the primary/cabin fuse box as well.

 

i think it would be also very use full to run a diagnostic check via obd2 .
with ether jaguar IDS/sdd or icarsoft for specific module and network codes ,
this may or will most likely uncover some info you require .

 

Yeah, I was thinking the same thing. It's looking more and more like a problem with the GECM. I thought we were on to something with the adjusters for the steering column and pedals, but then I dug a little deeper. The steering column adjustments, which always work, are controlled via the instrument cluster. The pedal adjustments, which go dead with the other stuff, go through the GECM.

Before convincing yourself the GECM itself is at fault, please complete the previously suggested checks for loose fuse sockets, loose connectors, etc. A loss of power will mimic a module failure, so rule out the basic stuff first.

After that, run a scan of the modules. A basic ODB II scanner won't help, as it can only obtain emissions-related information. You need something with IDS/SDD capability to be able to interrogate the individual modules. You will have to decide if you want to purchase a scanner with this specific capability (iCarSoft?) or take it to a shop for diagnosis. The dealer will obviously have the correct tool. If you'd prefer an independent shop, ask first if they have necessary IDS/SDD scanner. If they don't understand the question, try elsewhere.

Expect to see some fault codes from other modules, indicating they can't communicate with the GECM. Be aware this isn't necessarily a fault of the GECM proper. An intermittent loose connector or loss of power can affect the GECM's ability to communicate. Just something to keep in mind before shotgunning a replacement module.

Before tracking down a scanner, I have one other Hail Mary idea to consider. In the wiring diagrams, look at figure 01.6 again. This shows the four Switched System Power (SSP) relays in the middle of the page. Most of the naughty circuits (front exterior lights, dimmer controlled lights, etc.) get their power through SSP relays 1 and 2. If those relays had some pitting damage on the internal contacts, that could reduce the voltage available for a broad range of circuits. Kind of a long shot, but the GECM is probably expecting to see 12+ volts from any circuit before it will supply a ground. So if the GECM doesn't see exactly what it expects, it may not energize those circuits. It may not even generate a fault code, who knows. My free idea (and worth every penny) is to swap SSP relays 1/2 with relays 3/4. See if there is any change in symptoms. Please note how the relay locations on the panel are a bit confusing:

SSP relay #1 = Location R2
SSP relay #2 = Location R11
SSP relay #3 = Location R4
SSP relay #4 = Location R5

One last question, from the Thinking Out Loud Department:

Your initial observation was the intermittent failure of certain lights. Then we determined certain other circuits (such as the passenger mirror, that one dome light, etc.) also failed at the same time. What if you leave the headlights off (daytime, of course), go for a long test drive, and see if these other circuits still act up on their own? I'd be very curious if the lights have to be on for the other circuits to fail. If the headlights must be on, that would lean towards a low voltage situation because the lights draw a lot of power.

Speaking of low voltage, have you checked the system voltage while the fault is active? I'm a big proponent of a voltmeter thingy that plugs into the cigarette lighter. For all we know, your alternator output could be marginal and voltage drops a little bit under the load of the headlights. Then for whatever reason, the GECM is the first module to react to the low voltage, your lights shut off, voltage climbs back up with the load reduced, and then the cycle repeats. I'd be willing to gamble $10 of your hard-earned money on a voltmeter you can read while driving...

 

More free stuff to check, to make sure the basics are good. I am very interested to hear back if the fault is still active with the headlights off. I've already asked if you can monitor the voltage when this happens. Then I gets to thinking, and I've got one more thing to look for: AC ripple from a bad alternator.

​If you have a digital voltmeter, it's quick and easy to rule this out. The first link is for Mercedes, but the principles are the same on all modern brands:

http://www.pvv.org/~syljua/merc/TooSeptST07.pdf

http://assets.fluke.com/appnotes/aut...e/beatbook.pdf


Excessive AC ripple can cause all sorts of strange symptoms, often with no corresponding warning light or fault message. I would suggest spending 5 minutes to quickly rule out this possibility.

If at all possible, take the reading directly at the alternator, not the battery. Red meter lead on the big output wire. Black meter lead on the alternator case. Set the meter to AC (not DC) volts and start the engine. Select the lowest range that will let you see 0.5VAC. Anything more than that is a bad alternator.

Actually, you can start with a reading at the battery. If it fails, then you can skip the reading at the alternator, as you know it’s bad. But if it passes at the battery, repeat the test at the alternator to be sure. ​​​​​​You might think distance from the alternator wouldn't matter, but it does. The AC spikes are strongest at the source, dissipating the further they travel.