Insanity: Designing a vehicle with a bunch of sensors and switches that do nothing except prevent you from driving the vehicle.

Ok, I thought I could work through this, but I am at my wits end and about to go postal on Jaguar electrical engineers.

Background:

Recently bought a 2000 XK8 convertible with 65,000 miles. Flew to San Antonio TX to pick it up. Drove back to Hillsborough, NC. 1200 miles and surprisingly uneventful ride as far as the car went. Only one engine fault (P0455) which cleared with a half can of seafoam.

Not so good since we've been back. The car shut down a couple of times while driving (70 MPH). Pulled over and set for a while, and started right up. No codes. Drove fine for a while, and we will park it. Fairly regularly it would go into "Low Brake Fluid / ASC Not Available / Gearbox Fault / Failsafe Engine Mode" on its own. Still no codes.

Repairs made:

• Had battery checked and found it had a weak cell. Charging system good. Replaced battery with Duralast Platinum.
• Purchased a rebuilt throttle body from American Scientific
• Checked and cleaned every electrical connector I could locate.
• Cleaned all 4 wheel speed sensors
• Disconnected, cleaned and reconnected all ground lugs I could locate
• Checked every fuse in the car
• Received and installed rebuilt throttle body

Car ran well for about 50 miles, then "restricted performance" and codes P071 and P074 appeared. So I:

• Disconnected Air intake tube and checked all for cracks or areas of possible leaks.
• Replaced air filter.
• Removed and cleaned the MAF
• Discovered one of the clips on the air filter housing was nor clasped

The P071 and P074 codes cleared however, when driving now, it still randomly goes into "restricted performance" or "failsafe" which immediately resets when the key is turned off and restarted. Once when this happened I read a P1229, which cleared when restarted.

The car also still randomly goes into "Low Brake Fluid / ASC Not Available / Gearbox Fault / Failsafe Engine Mode" on its own and will not start. When in Failsafe, I have also tried to put it in neutral to see if it made a difference, but no change. Jiggling the shifter or key does not seem to have any effect either. Last time out, it also picked up P1637 and the MIL light is on.

Looking for suggestions on next step.

 

The early year cars, 97-98 prob as late as your year were know for ECM issues. My 97 pooped out with MANY of the same things you are seeing. A ton of random crap seemingly going out. Check the ECM's two large connectors, take them apart and reseat them, COULD be the issue there. I did the replace the TB gig with mine, never did work, took my old one back and put it on the car and sent out the ECm to autoecu.com and had them bench test and fix. That was about 4 years ago, been running fine since (I sold it but know the current owner). Just with ALL those diff things going on I would put my next check on that maybe being the issue. It costs like 60 bucks or so to bench test, if it passes then you know that is not it and they will send it back to you. From there, GOOD LUCK.

 

when mine first started acting up it was small things here and there miles/weeks/months apart but eventually it just stopped running pretty much, warning lights, stumbling, no power.

 

Thanks. I will check that out tonight

 

Re-seat all the relays in each fusebox, including the engine management fusebox under the hood on the passenger side near the windshield.

Also, check the power connection to each fusebox is clean and tight, as well as the power connection to the megafuses at the rear of the trunk.

 

"The car shut down a couple of times while driving (70 MPH). Pulled over and set for a while, and started right up. No codes. Drove fine for a while, and we will park it. Fairly regularly it would go into "Low Brake Fluid / ASC Not Available / Gearbox Fault / Failsafe Engine Mode" on its own. Still no codes."

In the past, I had a very similar set of circumstances. The car would just quit. then start right back up after a few minutes like nothing ever happened. Had the same exact warnings too. No codes.

In my case, the strain relief for the power cable that feeds the under hood fusebox (not engine management fusebox) had failed.... and the metal strap that attaches to the internal circuit board (inside the fuse box) had torn away from the copper traces on the printed circuit board. All I had to do was take it apart and solder the metal strap back to the PCB, and use some epoxy to fix the strain relief.

In any case, had all the same symptoms, so take a close look at that fuse box and its supply/ground connections.

 

Alan, good work and great find, wish you had a picture or two of that process. Welcome to the Forum.


Wayne

 

Y'all are awesome! I am just reading Alan's message this morning but turns out he was on to something.

I had some success last night but still have some issues.

I started out with Tim's recommendation to reseat the connectors on the ECM. Based on the looks of that unit and a couple of missing bolts on the cover, it seemed apparent someone has already had their nose in there:



Then I moved on to the relays in that compartment. The first one I looked at had a spliced wire, although the spliced wire was cut:



So ok, maybe someone hooked up a kill switch or something. Sure enough there was a momentary switch under the dash with the same wire attached to it:



So I removed the blue wires and taped up the splices. I would be interested if someone knew what that switch could have been used for,

I finished cleaning and resetting the remainder of the relays in that area. Thinking that maybe I found the culprit, I started it and decided to go for a ride. As I was buttoning up, I went to put the cover on the under hood fusebox, and when it snapped into place, the car immediately shut down and went into failsafe mode:



Aha! I found a culprit. I did not take it completely apart to check it out, but only cleaned and reseated the main lug and relays.

Then took it for a test drive. During a hard acceleration, it went into "restricted performance" and showed codes P1637 and P1642. From some threads, it appears that these could be related to that fuse box. I will look into that box further tonight.

 

Ok, I've been gone a while trying to work some bugs out.

So I was still having some intermittent issues so I pulled the fuse box apart to see if I could find any loose connections:







I didn't see any loose connections, nor did I see how I might access the main lug connection. So I cleaned everything and put it back together and reinstalled it. The car has only gone into failsafe a couple of times since I put it back together. When it does, if I open the bonnet and tap the top of the fusebox, I hear a double click and it will be fine again. (My wife loves this procedure at the grocery store).

So I have 2 questions:

1. Has anyone have ever had a relay stick periodically, or does anyone think this could be the issue?

2. It appears that there is a relay missing (see first photo). Can someone tell me what is missing, or if it is missing?

Thanks,

 

Just to answer your question #1, yes relays can stick. They are all the same, swap two at a time and see if the problem moves.

 

"So I have 2 questions:

1. Has anyone have ever had a relay stick periodically, or does anyone think this could be the issue?

2. It appears that there is a relay missing (see first photo). Can someone tell me what is missing, or if it is missing?"

A relay can stick. These relays are not sealed, so the contacts can and will corrode/degrade over time. A relay can also be intermittent for many reasons... including sticky contacts, corroded contacts, a break in the winding that creates a magnet (i.e. the magnet wire), and even due to the breaks in the wires that control the magnet or the circuit that is being controlled.

There should be 1 missing on some cars, including my 2000 XK8.

Since it seems sensitive to vibration, look for hairline cracks on the copper traces on the printed circuit board. A hairline crack will usually manifest itself as intermittent behavior that changes with vibration, shock, or even temperature as the metal expands and contracts. Use a magnifying glass.

Look for cold solder joints, especially where the power cable/strap solders to the PCB. But check them all. Use an ohm meter. The quality of a connection is impossible to know by looking. Test it! (although cold solder often shows a sign, its not a given) - use a magnifying glass.

You might want to get some electrical contact cleaner and clean all the connection on the board and on the connectors in the car.

The relays are pretty cheap, around 4 to 6 bucks locally, so I always have a few extra handy for just such troubleshooting. That way, I can never mix up the two I swapped.

Hope this helps.

Alan

 

Hi, I know this is an old post but I think that missing relay is for power headlight washers on my 2001 XK8.