My MY2000 XK8 (67,000 Miles) has been flipping in and out of Engine Failsafe Mode for a few weeks while I try to systematically sort out the problem (There were Pending Codes for enriching both banks but no current codes, now there are no codes at all related to this issue, just the message popping up. I cleaned the MAF, plenum is tight, brake booster line seals, full load breather, part load breather, replaced the FPR vacuum hose, etc. - all to no avail thus far)

This morning, however, it gave a Restricted Performance message and CODE P0354 - Ignition coil (A1) primary/secondary circuit malfunction.

JTIS says," 1) ECM to Ingition module primary circuit open circuit, short circuit to ground, high resistance. 2) Ignition circuit module ground circuit open circuit, high resistance, 3)Ignition module/coil failure"

A couple of questions:

Which coil/cylinder is A-1?

It is typically a full on coil failure or a short somewhere else?

While researching this I found a reference to a COIL ON TESTER tool. Sounds like it could be handy. Where to get one? Expensive?

Thanks! This car is exasperating!

 

P0354 is an actual coil circuit fault. Have any of the ignition coils been disconnected while the ignition was on? That will set a circuit fault. If you have a coil failure that would set P0354, you should also have a misfire fault P0301, because a dead coil will be a misfire as well. A-1 is bank one [RH], cylinder 1 [Frt].

The rich system faults you mentioned need someone to check out the fuel trims and trace down that problem.

Good luck!

 

XJRguy,

Thanks for the comfirmation. No misfire code was present, only P0354. I went ahead and ordered a replacement coil.

I'm at a bit of a loss as to what to do with the fuel trim situation. I could throw some money at it and replace the MAF but only because that seems to be the only thing left to do. Do you have any further knowledge on fuel trim?

 

Do you have a scantool or just a code reader?? If you can read Mass Air Flow, or find someone who can, use the attached pic as a guide. Read your Mass Air Flow under the four conditions. If the idle readings vary more than about 1 g/sec, or the high RPM readings vary more than about 3-4 g/sec, then the Mass Air Flow is suspect. If your MAF reports more than the chart figure, Rich System Codes can be set.



Be careful with the drive reading, hold the brakes really hard.

Cheers,

 

Any possibility of sharing where that chart comes from? Whatever document that is, looks potentially very useful.

 

You bet it is. It's nothing official though. Because diagnosing MAF sensors can be challenging, several years ago I began charting sensor readings on new sensors following a repair. It has saved my butt many times since then. Like I said though, it's just a guide to help the diagnosis, not a hard, fast specification.

Cheers,

 

Thanks! I have a reader that's part scan tool, I'm pretty sure I can grab the reading. I'll report back.

 

any table for the 4.2 engines?

 

 

if there were a thanks button on that post, I'd give you a click! maybe later.

 

Well, I replaced the coil and all was fine for 100 miles. The next morning the same problem occured...P0354 code, Restricted Performance. Is i9t possible for there to be some sort of open circuit that's burning out the coil over night?

Any ideas?

 

It's probably not burning out the coil. You probably should start tracing the circuit to that coil. Possibly there is a wire chafed somewhere along the line. That could explain why it's not perfectly consistent.

Happy hunting.

 

Probably never was a problem with the coil - I can swap the new one to a different cylinder and the problem remains at the A/1 position...I thought about doing that earlier but was pretty confident in the P0354 code...Wouldn't hurt to pull that plug and have a look.

More to follow...

 

I would hope its wiring since not the coil since you finally swapped, because if not that useally meens the driver (-coil trigger) in the ecu is faulty. Good news on that though is there are companies the can repair yours if thats the issue, going rate is $500

 

Well, you can swap the plugs, but I don't think it will show you anything. The P0354 is not a performance fault, it is a circuit fault, meaning the ECM has interpreted something is wrong with the coil circuit electrically. That can be a bear to find sometimes.

Cheers,

 

I was just wanting to look at the condition of the plug to rule out something simple. Your observation about performance vs. circuit fault obviates that need, however.

I'll have to get out the wiring diagram and see where the coil wires trail to. Are we thinking a simple old fashioned short or something internal to an electronic component which requires electronic diagnosis?

I'm going the put it on a full on diagnostic machine and see if something further is revealed.

 

The easily viewed coil wiring is all tidy, dry, clean and nice, no issues at all. I had it idling and moved, tugged, etc. every wire all the way back into the loom and the loom itself down to whatever box it terminates into. No codes Current or Pending. Just a rough idle and Restricted Performance with CEL.

I disconnected the battery and grounded the harness to hard-clear everything. I'll give it another try in a hour or so.

 

I buttoned it up after letting it sit overnight with the battery disconnected. Starts fine, smooth idle, no codes. I'll run it around to get it up to temp. and then begn diagnosing the original problem - MAF - with the handy chart.

The problem will return for Round 2 soon I'm sure.

 

I took it out this evening - here are the MAF readings compared to the "Good" readings in the chart, from above:

"Good" Observed
Park Idle 5.1 gm/s 5.21
Park 2500 RPM 17.0 16.66

Drive Idle 5.9 5.88
Drive 1500 RPM 39.3 15.00

(Acceptable range = +/- 1 g at Idle; +/- 3 to 4g at High RPM)

Seems something is amiss in the MAF sensor.

 

I see the chart reformatted itself into gibberish, I'll create a spreadsheet and resubmit it. The take away is that the MAF should read about 39.3 in Drive at 1500 RPM, mine reads 15.0...