Fine friends,

I have some good news, and some bad news. The good news is, when it starts, the car runs beautifully; smooth as glass with the new suspension, tires, and brakes, and the really good news is I managed to finally get my state inspection to pass, and will finally get some plates this week!

EDIT: This is my 1997 XK8, with which I have done quite a bit of work recently; it is really running in top form except for this strange engine fault. Temp is perfect (observed with an OBD scanner) the engine runs smooth, I resoldered the ABS unit and the ECU cap's with the help of a professional, and many other things unrelated to electrical.) /EDIT

The bad news, I had to convince my mechanic to do the test with a constantly running engine, because the dreaded Engine Fault has resurfaced once again, seemingly on any case where the engine has warmed and been ran for a considerable bit of time. (This happened especially after running about 30km for clearing the catalyst tests.. so I had to do it twice!)

On our previous episode, I found an Engine Fault with no accompanying P-codes on my inexpensive / cheap scanner. Baffled by this mystery, and at the advice of many members on this forum, I removed the ECU for inspection and re-capping. Although I did find original 1996 capacitors installed, there was no visible PCB damage. I replaced them all as a matter of course, along with ABS module repair, and put it all back together. I had one restart without issue, but the following day the Engine Fault appeared again.

I have since obtained a better scanner, iCarSoft i930, and have observed a little more specifics of the case where it happens:

• Engine cold, not an issue, seems to start up fine after resting overnight.
• Engine hot after a drive, if I put in Park and shut off the car, the Engine Fault is likely to appear at the next restart event (but not 100% every time; this may or may not be related to ambient temperature, it has fluctuated quite a bit here lately. Or possibly just luck, for instance, after resetting via battery cables three or four times I was able to get it to restart off the side of the road, and drive home.)
• While still with warm engine, after a reset via touching the battery cables together;
  • Key on, engine off, Engine Fault does not appear - it has been cleared by touching the cables.
  • Crank approximately three revolutions, the amber light appears and Engine Fault returns.
• The Engine Fault has never appeared whilst driving the car, and the car itself shows no other symptoms.

And here are the codes the scanner managed to pick up:

• B1595: Ignition switch, illegal input code
• B2368: Column adjust switch, out of range
• U1041: SCP vehicle speed signal - invalid or missing data
• P20ee: Fault code not found in database (????)
• U1135: Ignition status not obtained
• B1965: Seat drive, fore/aft out of range low
• B1713: Seat switch, height lower
• P0706: Transmission range sensor circuit range/performance (This did cause "limp mode," but I believe this is unrelated to the Engine Fault.)
• P0790: Mode switch malfunction

In the past, my experience with a crank / no-start with fuel injected vehicles has almost always been a crank or cam sensor issue. But those would likely have P-codes accompanying them. However with the above DTC's, the two Ignition related codes seem to point toward the ignition module as the culprit. I'd really like to know any troubleshooting methods I can use to confirm or deny this, as it is a rather expensive part. Regardless of cost, I prefer to learn thorough diagnosis rather than part swapping in any case...

As usual, I welcome all suggestions, and thank you all in advance!

 

The D4 switch is your problem. (P0706)
Out of adjustment or 2,3,4 plastic selector disc broken.
D4 switch damaged or displaced?

DTC guide for you.

 

Thanks - I inspected the disc and also performed the cable alignment procedure, neither of which helped or made any difference (though, the cable was off by about 2 turns of the mounting nuts under the J-gate; seemed to make the letters light up a bit more accurately to the transmission) I've also cleaned the switches with contact cleaner, although they weren't all that dirty in the first place. I should also mention, the condition occurs without using the manual / left side, if that makes any difference here.

So in fact, according to the DTC guide, maybe this is the rotary switch, unless I'm missing another check here;

I don't suppose there are any definitive tests I can perform on the rotary switch that anyone knows of, before I just try swapping it....?

EDIT: I'm going to follow this thread https://www.jaguarforums.com/forum/x...s-like-139825/ and take mine apart, look for internal damage. I didn't realize they came apart without cutting... /EDIT

 

the manual lever position switch is an encoder switch, the chart is in service info.

L1-L4 on the MLPS and the D4 microswitch are rationality checked together that’s why it sets the same DTC. any dubious input sends you straight to 5th gear and max line pressure.

L5 is only for the ecm and if it’s open the injectors never get pulled to ground on cranking

http://www.jagrepair.com/images/AutoRepairPhotos/Rotary%20Switch%205HP24.pdf

 

After re-checking everything, I'm not sure I did the cable procedure (this morning) correctly; I followed these steps;

• Loosen both shifter cable nuts to end of thread under J-gate
• Disconnect pin from trans lever
• Back shifter lever all the way to P (this thing is a pain to work with meaty hands)
• Forward two positions, it's pointing pretty much straight up at that spot
• Hand-tighten the nut (again, meaty hands = pain and humility)
• Re-confirm shifter in N with a bit of slack both ways
• Snug the nuts on the cable, again confirm N stick position
• Simultaneously turn both nuts for equal tightening distance until tight
• Tighten the parking lever nut

... But I noticed, when I carefully / slowly move the stick, it engages R just before it hits the indent in the J-gate; then I noticed shifting up from N to R, it engages as I drop into the indent, as expected. Is this normal? Or does that indicate I got it wrong? i.e. Do all you folk's Jaguars engage *just before* the indent from P to R, if you (have ever) tried this?

Also, I just want to confirm, is the P0706 enough to trip BOTH the transmission fault and engine fault? The real issue I have right now, is being stranded with an Engine Fault and crank/no-start. I can't even take the car to the gas station to fill it up, without worrying about this. The last time it happened, I was stuck in the mechanic's driveway trying to restart to pull in for inspection, and was blocking his traffic because I couldn't get it to start, even after four or five attempts with the battery cable touch-to-reset trick. The transmission fault goes away, but it keeps reading Engine Fault until I somehow get lucky after a reset, and it starts. It just seems like there must be some other component that is causing the Engine Fault, after it has warmed up on even just a short drive. But maybe I'm wrong and it is related - that's fine, I just really want to focus on the engine fault itself first, as it is completely disabling vs. at least having a limp-home mode.

Thanks,
-Jim

 

stop touching the battery cables together it doesn’t do anything except clear dtcs.

like i told you if PNP is open the car will crank and not start, try that first, look at the wiring diagram figure it out and come back…there is no silver bullet answer for your problem

 

Duly noted; I did not realize this. I thought it cleared a memorized fault, but now I see, the engine will fire absent of present issues.

I went at it today, thinking to trace the lines and test at the wire harness. I found a few behind the throttle body. Following the cable from the rotary switch, it seems to head to the farthest harness in the pack of 4, but I can't be sure as it is quite difficult to folllow past a point. I have attached a photo of what I think is the correct harness, however, it does not seem to match up to the diagram; In the diagram, it states BY S RB Y W BK G but in the harness (photo attached,) it seems to have White-Red which is not listed in the diagram. Can anyone tell if this is the right connector? Also attached, I have the other three harnesses, none of which are a set of seven and none of which seem to remotely match the diagram. However, I do not know of a legend for this diagram so I am basically assuming things like R=red, BK=black, et cetera.


Is this the correct harness?


The other few I found at the firewall behind throttle body

@xalty I appreciate your point, well taken, and I apologize for being a bit of a ninny there.

 

Jim - not sure where you got that sequence? The '97 (&98) EG shows:




...which does match if you follow the connector EM47 around anticlockwise from top right.

 

Have you checked the exposed ground connections?

 

Xalty's linked doc earlier in the thread. Must be from a later model or something? I didn't see years indicated.

Thank you for the correct diagram, now I am eager to check continuity & consistency across WR / G after work today. Will post what I learn.

 

Doh!
In its infinite wisdom, Jaguar started changing the colours around for '99 on. 2000 is different again...

 

Well, I have sorted the transmission errors, with a final cable adjustment that seems to be just right. Fantastic, now I can shift thru all the gears, back and forth, no issues, no codes.

Now, after another test drive, again I am faced with the engine fault. Still no transmission codes though, so I suppose that's at least a little bit of good news.

I have pulled fresh DTC's, and (again) there are no transmission codes, or ECU codes. The BCM still gives me B1595 and B2366, however.

At this point, I am confident that the shifter and cable are correct, and also the rotary switch. I also verified I get a needle bump on RPM (very slight) when cranking, which seems to indicate the cam/crank sensors are ok.

I went as far as contacting the dealer nearby, willing to throw in the towel and pay thru the nose for a diagnostic, but they declined due to the vehicle age and "not having the expertise or tools at hand" to help.

Is there any guide somewhere that provides a diagnostic flowchart of what can cause, specifically, the Engine Fault message on the dash? The battery is strong at 12.5v, the engine cranks normally, but it just prints Engine Fault and does not attempt to fire at all. When it ran, it ran quite beautifully, no miss or performance issue of any kind.

I'm at a bit of a loss, so any help is greatly appreciated. Thank you all.