I have a 2004 XJR, after a short trip when I restarted her, no CEL or other warnings, a few seconds later, error message appeared, I thought I smelled an electrical short and turned it off. I tried once again to restart but even though the engine would turn over, she never fired.
I had it towed back home and ran the OBD scan. I received the failure to communicate with ECM, however the other systems scanned. Downstream O2 error(nothing significant) and also an open circuit on rear passenger air suspension. Fuel Rail shows pressure. How would I sort out the ECM whether its a failed unit or perhaps a wiring issue.
This is the first time I have received the failure to communicate message and the obd scans the other systems fine.
ANy help is greatly appreciated.
Thanks!

 

If it's a 4.0 then Search on bore wash.

 

Thanks, it is a 4.3 Supercharged. i930 says no comm with ECM, but all other systems scan. I will try the borewash fix to rule that out as a problem.

 

I guess 4.2???? If so, not likely to be bore wash.

Try another OBD tool like the elm327 (about $10). The 930 is known to be a pain at times.

 

Just a few random thoughts:

1. What was the error message that appeared on the instrument cluster when the car stalled?

2. The burning smell doesn't sound good, but it might be worth carefully checking all fuses in all the fuse boxes in the event there was a wiring short.

3. You have fuel pressure. Have you checked for spark?

4. Can your i930 read the proprietary Jaguar B (Body), C (Chassis) and U (Network) codes? Might be some clues there.

5. A known issue is water accumulation around the electrical connector for the ECM, due to the drain below the connector becoming clogged with leaves, seeds, etc. The ECM is behind the glove box, but it's connector is accessed from the engine compartment below the cabin air microfilter housing. It would be worth checking for a clogged drain and disconnecting the ECM connector to check for corrosion on any of the pins (use zero-residue contact cleaner spray to flush both halves of the connector, and allow to dry before reassembling). Disconnecting the connector requires a 5-point security/tamper-proof Torx bit with a hole in the center to fit over the pin in the center of the head of the connector screw. I bought a set of 5-point security/tamper-proof Torx bits for about $20 on eBay.

Please keep us informed.

Cheers,

Don

 

Thanks Don,
The car started fine, it went maybe 30 feet in the parking lot, and I smelled ozone like a short had occured, and the restricted performance message came up then car died.
I 930 shows other systems just not ecm, i can look at my rail pressures, air suspension info, etc, but get the failure to comm for the ECM. I will see k the security torx bits to remove the connectors. Years ago I sold these screws and bits to prisons and the military and possibly I still have some samples but i doubt it.
Good tip on the contact for the ecm problem.
I will check the fuse and see if that is blown.
Hal

 

Hal,

You can download the full Diagnostic Trouble Code (DTC) Summaries manual at the link below. It will give you an idea of what sorts of malfunctions can trigger restricted performance (look for codes that reduce maximum engine speed).

https://www.google.com/url?sa=t&rct=...03388427,d.cWw


Cheers,

Don

 

No luck in downloading trouble codes. Manually checked the spark and no spark is being sent to the plugs. So with no spark to any plug or coil pack. Where is it best to start chasing the issue. Since it is affecting all cylinders, I am thinking either capacitor some other element that would affect all cylinders from receiving fire. Any ideas on best places to start are greatly appreciated.
Thanks in advance.
Hal

 

Hi Hal,

With the key in Position II (ON) you should have 12V at the RW (Red wire with White tracer stripe) at every coil. The same 12V should be present at the RW wire at the ignition capacitor.

The B (Black) wires are the ground for the ignition modules in each coil and for the capacitor.

The ECM grounds each coil in sequence to fire it, so each coil has its own individual ground wire with a distinct color code. See the schematic in the 2004 Electrical Guide, which you can download at the link below courtesy of our member Gus and his website, jagrepair.com:

2004 X350 Electrical Guide

Cheers,

Don

 

Thanks Don,
Exactly where is the ignition capacitor located? I have a break in the weather tomorrow and will spend some time checking the voltages to the COPS. I did print out the electrical schematics and they are most helpful. I pulled the front relays and saw no external marks of shorting, swelling etc. Whatever the issue is, no cylinder is getting spark. I will check voltages tomorrow and report back. The center bulkhead location seems to indicate the capacitor is buried beneath the cover behind the engine? Which looked very tight to access. The ECM location is on passenger side bulkhead, in the engine bay or in the car interior?
Thanks,
Hal

 

I'm not sure, but as far as I know it's just a radio interference suppressor, so it is probably small, and not your problem.

Failed relays quite often show no external evidence of their failure, so you either need to test them electrically or swap in known working relays.

The ECM is in the passenger compartment behind/below the glove box (on LHD cars), but its electrical connector is on the engine bay side of the firewall/bulkhead below the cabin air microfilter housing. Use a flashlight to look below the microfilter housing for any signs that the water drain may be clogged with leaves, seeds, etc. If it is, water can pool up around the ECM electrical connector and cause problems. I don't recall a report of this preventing spark at all eight cylinders, but it's certainly worth ruling out.

Cheers,

Don

 

Never heard of the capacitor going bad, though anything's possible. I wouldn't rush to find it. If the PCM isn't wet then it's another last suspect. That leaves plenty of others, sadly!

 

Don,
Thanks again. I checked COP red leads to ground with key in run position and no voltage was indicated?
Does this narrow it down much or am I still chasing rabbits trying to sort this out?
What should I check next?
Thanks in advance.
Hal

 

If you have no voltage at the coil harness connector Red/White wires with the key in the run position, the next thing to do is work your way upstream until you find voltage.

If you don't have much experience with the Electrical Guide, I'll walk you through the next steps so you get a feel for it.

The ignition coils are shown on Part 2 of the Engine Management System schematic for the Supercharged (S/C) engines, which is page 69 of the pdf manual. Notice that all the RW wires for the coils come together, and to the left of the points where they join is a circle with the number 138 and the letter E inside.

Look at the figures along the bottom edge of that page and you'll see squares, which represent battery power circuits, triangles, which represent logic circuits, and circles, which represent ignition-switched power circuits. The E in the circle to the left of the coils indicates that this is an Engine Management System power supply circuit, and the number 138 tells us where that wire connects on another diagram.

Now find the circle at the bottom of the page with a number range that would include 138/E. That circle has the number range 106/E to 143/E, and the Fig. 01.8 next to that circle tells us where we need to look for the continuation of the wire that feeds power to the coils.

Figure 01.8 is on pdf page 53. Find the circle with 138/E. To the right are pentagons with numbers that indicate the other Figures that include parts of this circuit. To the left follow the line to the fuse symbol labeled F30 10A, and the relay diagram labeled Ignition Coil Relay. Note that both the fuse and the relay are enclosed in a dotted rectangle that is labeled Front Power Distribution Fuse Box.

Now move up to the previous page, 52, which lists all the components, connectors and grounds for Figure 01.8. The location of the Front Power Distribution Fuse Box is given as "Engine Compartment / RH Front."

The location of the Ignition Coil Relay is given as "Front Power Distribution Fuse Box - R7." R7 is the number of the relay in the FPDFB.

So that's where I would look next. Check fuse F30 and if it is good, the relay is the next suspect. R6 is the Front Fog Lamp Relay and if its size and current rating are the same as the Ignition Coil Relay you could try swapping the two relays to see if you get power to the coils. If not, you'll have to check for power on the appropriate terminal of the Ignition Coil Relay socket.

Please keep us informed.

Cheers,

Don

 

Thanks Don,
Swapped the relays and no change. Fuse 30 is good. SO will check the pins for voltage on the relay terminal.
Hal

 

The schematic for the coil should show which terminal(s) should have 12V when the key is in the ON position.

 

Don,
I checked voltage today on relay and I had 12 v there. Going back and rechecking the Coil this time using the pins instead of common ground I showed 12 volts a the coil.
I plugged in the relay and immediately heard the connection when I swapped the relays, so both relays in the front power box of the R7 variety appear to be working.
Before further electrical I need to do a battery change on ym voltmeter as it is acting squirrely with voltages and I ma having a hard time zeroing it out

SO with power to the relay and the coil, what next?
I so appreciate your help!
Hal

 

Hi Hal,

So that's good news - you do have 12V at the coils. But the car still won't start?

My next question would be: how did you manually check for spark before? It would be worth checking again.

If you have 12V at the coils but no spark, the problem could be in the ground circuit for the ignition modules (the black wires off the top of my head), or in the control circuit for the coils (the wires that connect to the ECM), or the ECM may not be grounding the coils to fire them for some reason, one of which is low battery voltage while cranking the engine.

Thinking about your ozone smell, have you inspected all the wiring you can access for any signs of arcing or burning?

Cheers,

Don

 

yes, I inspected where I could but as you know, not much is visible on these cars. I checked under the dash with a remote camera.
The spark I checked with a spark checker device from the autostore, but I am suspicious that the unpainted bolt on the engine is not a ground now and that being the case, I need to recheck using a better ground
Basically the device is nothing more than a light that makes up the connection between the coil and the ground, pretty simple and I have used them succesfully in the past, but this is not the past
Battery is just two years old and measures proper voltage. I keep thinking fuel, compression, spark and everthing else is tuning.That smell of a short circuit tells me whatever shorted it completely shorted as it no longer has that odor when i turn it over
Thanks for the advice and help.

 

Yes, a true ground is essential. One of the ground points behind the headlamps would be good but you must be sure your clip or probe is touching metal and not just paint.


The critical measurement is the voltage while cranking, and most voltmeters cannot react quickly enough to show you the true voltage sag. Many cars can start with just 9.5 volts or so, but if the voltage on your Jaguar falls much below 11 volts the ECM may not trigger the coils to fire. One thing our member Box discovered is that the charging voltages in the X350 are higher than normal to meet the requirements of the original batteries, which used silver calcium technology. Silver calcium batteries are not currently being manufactured, and most lead acid and AGM batteries cannot tolerate these higher charging voltages with the result of a shortened life. The only currently-available battery Box has been able to identify that can live on the higher voltages is the Exide NASCAR Extreme Silver Shield available at Home Depot (currently $119 at our local HDs).

The failure to communicate with the ECM is a major clue, and probably the reason you haven't been able to scan any fault codes. Is there an independent mechanic in your area with a diagnostic scanning system capable of reading the proprietary Jaguar fault codes? That may be the fastest means of finding some diagnostic direction.

Cheers,

Don