Hello Gentlemen,

After completing the following, I’m afraid the intermittent blackout of the dash and headlights still persists.
When I drove the car this morning I had a few minutes where “the entire system switched on”, so (for what I believe is the first time) I had the pleasure of feeling what power steering feels like.

What I did…
• I tested both the F30 and F20 fuses by checking if they were tight fits and swapping them out for new fuses that I had on hand.
• I also tightened any bolts which could be grounds near the GECM and primary junction fuse box.

Karl, to answer your question, the problem can be there the moment the car is turned on— without having turned on the headlights. I know the problem is there the moment I get into the car by seeing that the center dome light isn’t automatically on.

What I plan to do…

Plan A
• Swap SSP relays 1/2 with relays 3/4 to see if there is any change in symptoms.






Plan B
• Have a reputable Jaguar shop here in Minneapolis (check via obd2 with either jaguar IDS/SDD) for specific module and/or network codes.
• Have the system voltage checked– AC ripple from a bad alternator.
I’ll have them take the reading directly at the alternator, where they'll set the meter to AC (not DC) volts and start the engine.
I’ll have them select the lowest range that will let them see 0.5VAC. Anything more than that is a bad alternator.
• I’ll have them check for loose grounds, fuse sockets, loose connectors.
• I’ll have them check the FECM earth and all front earth points

 

No meter of your own? Got to laugh at myself in that case. I've got six multimeters, one oscilloscope, and four ammeters. Therefore, all problems are electrical in nature...

Even the cheapest multimeter will work for the two checks I recommended. Might be worth picking up a $10 HF special before taking the car to a shop. AC ripple is definitely a long shot, but easy enough to rule out. Low system voltage is a little more likely, and just as easy to monitor.

If you take the car to a specialist, they may look at you cross-eyed if you talk about AC ripple that you heard about from some guy (albeit a handsome one) on the internet. Things might go smoother if you just report the symptoms and let them decide how best to proceed. In strange cases like this, I like to verify the basics before digging too deeply. A professional shop, on the other hand, may just want to get down to brass tacks and replace the most likely culprit. Can't say one tactic is better than the other.

If the shop does want to check for AC ripple, hopefully they.have an oscilloscope. It's much better at capturing the voltage spikes than a regular multimeter. Most meters are expecting to see a relatively smooth sine pattern, and thus may not catch quick spikes. No such shortcoming with an oscilloscope.

 

Hello Gentlemen,

I’m afraid the intermittent blackout of the dash lights, headlights and misc. other electrical components (which are constantly changing on a day by day basis) still persists.

What I’ve done…
• I swapped SSP relays 1/2 with relays 3/4 to see if there was any change in symptoms.
• I went to a garage here in Minneapolis (with 45+ years experience in servicing all British makes), where they tested the battery and alternator– they said both tested fine.

What I'm planning to do…
• Schedule for the garage (to check via obd2 with either jaguar IDS/SDD), for specific module and/or network codes.
• I’ll have them check the GECM earth and all earth points.

What I imagine I might need to additionally do, pending your thoughts, is swap out the GECM.
My questions on the this action include…
• Can a different GECM be replaced?
• Can I have the GECM preprogrammed if I give the seller the appropriate information, or do I have to have it programmed once it’s installed?
• If it’s possible to program a GECM replacement, what type of software is needed?
(is this a dealer specific service or can independent garages do this as well?)

Your continued willingness to provide additional suggestions is greatly appreciated.
Brian

 

Brian,

Was the fault active at the time? Chasing intermittent problems can be very trying. I still wonder if you've got an intermittent low voltage problem (reasons unknown so far), and the GECM is the first module to react negatively.

A shop can't afford to drive the car for several hours in hopes of catching a glitch, but you can. This is where we amateurs have a huge advantage over the professional. I think you're doing yourself a disservice by not hooking up an inexpensive voltmeter and going for a long test drive. Even if you have little electrical experience, virtually none is needed to monitor a meter display on a test drive.

Find something and you'll possibly save yourself a lot of money. Find nothing and I look foolish. You can't lose.

BTW, thanks for humoring me by swapping the SSP relays. I'm just trying to rule out some basics (on the cheap) before condemning the GECM.

I'm not sure what (if any) programming is needed to replace the GECM. Can anybody else chime in? I vaguely remember somebody replacing a similar module (RECM?) without any trouble. IIRC, the secret was to find a used unit (eBay?) from the same year with an identical part number. Please don't quote me on that, though, and wait for a more definitive answer.

 

agreed .
at least check the fuses of the offending circuits during the power outage for power . to rule out a fuse box issue
also you could check the front park light plug during the outage to see if there is a positive power supply during the outage .
also pointing to the fuses being good.
because the circuits light sockets are always powered with the key on and are switched on using the negative ground wire via the control module .

then if your ground wire to the light sockets across the lights controlled by the FECM/GECM is not grounding when commanded , that would point to the FECM/GECM being faulty .

i have swapped an RECM with a used matching part no# one with no programming required, id expect the same for the front one .
ether way they can be re- configured and re- programmed via IDS/SDD.

 

I almost missed this clue. See figure 05.2 in the wiring diagrams:

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


The variable assist power steering is controlled directly by the GECM. At low vehicle speed, the power assist is increased to help with parking, etc.. At higher speeds, the power assist is decreased to prevent accidentally oversteering. So one possibility is a problem with the GECM itself not letting you have maximum assist when needed. That would make the steering effort feel especially heavy.

More details in this training guide, see pages 32-33:


http://www.jagrepair.com/images/Elec...E%20Update.pdf


Unfortunately, I couldn't find any details of what is the default steering effort with the loss of a signal from the GECM. Do you get maximum assist? Minimum? Something in the middle? I wish that guide has more details, as that would be a huge clue. This leads me to another possibility:

A slipping serpentine belt - This would cause a double whammy of low output from the power steering pump (reduced power assist, i.e. heavy steering as you noted) AND reduced output from the alternator. You'd also have reduced output from the AC compressor and coolant pump, but you probably wouldn't notice those symptoms at this time of year.

So for all we know, your alternator may not have 100% capability at all times. The belt may grip just fine at low engine RPM, which is probably the situation when the shop tested the alternator. Increase the RPM and increase the electrical load, and the belt may start quietly slipping and the alternator output drops. The system voltage may be dropping low because the alternator output could be dropping under normal driving conditions, which are different from the shop testing conditions (stationary, engine at idle). That's why I've been harping to please measure the system voltage when the fault is active. I hate to sound like a broken record, but this is very important. Remember, the shop can't take the time for a long test drive to capture a glitch, but you most certainly can.

I get it, the GECM itself is the most likely fault here, but I'm still trying to verify some basics first at minimal cost.



This circles back to the possibility of low system voltage. If the system voltage was low before start (for reasons still to be determined), this could explain the lights misbehaving even with the engine off. Once again, a voltage reading when the fault is active would be a huge help! Notice how I keep dropping that hint...


Here's the plug-in voltmeter I keep hooked up in my car. For a whopping $14, it will provide the info to make me stop asking about the system voltage while the fault is active. If voltage drops below 12.0V (should never get that low with the engine running), it will start beeping, so you don't even have to watch it constantly. This little doohickey works great, except the blue digits can be hard to read in the sunlight. Still, this should give you a general idea of what is available:




On my car, I keep this plugged in at all times. Power to the lighter switches off with the ignition, so it won't drain the battery when the engine isn't running.

No electrical knowledge is required to operate this meter. You only need opposable thumbs to open the package and plug the meter into the lighter socket.

 

Thanks guys. I've heard you all along.
I'll install a voltmeter and get back to you with the results.
Much obliged Gentlemen. Much obliged.
Brian

p.s. love the link Karl.

 

So installing the plug-in voltmeter was more complicated than I thought?

Any updates?

 

Hi Karl,

I'm expecting the voltmeter to arrive today.
I ordered the one you provided a link to, because it looked like the best one available online.
It was sent via snail mail from China, so it's only arriving now.

I had a very promising piece of information today from a new garage that I've sourced.
They tested the voltage going in and coming out of the GECM as being strong/normal.
When they tested the voltage running through the GECM itself, it was approx. 60% full strength.
They've pulled the GECM in order to get the part number– which needs to match.
I'll keep you posted on the results of this find, along with whether or not it needed to be reprogrammed.

 

Mission Accomplished!
Sorry for the delay in posting the results of trying to figure out my intermittent electrical problem with my headlights and dashboard.
After replacing the GECM with a used one, where I made sure to match the part number exactly, all electrical problems disappeared.
The GECM was $52.00 online.
The labor cost was $75.00 – thank you Eurocharged Minneapolis.
Many thanks to all of those who helped guide me through the exhausting process of sorting this glitch out.
Now onto solving (which I'll post separately) why my functioning Alpine speakers are not receiving power from a functioning Alpine amp.

 

Thank you, thank you, thank you for the update!

Was the new GECM plug and play, or did the shop have to do any programming?

 

There's no programming required, if you match the part number exactly.