Driving to lunch today, 3 up in the XJR. Stopped at a traffic light. Sat for 20 seconds..... ASC/TRAC NOT AVAILABLE warning appeared (Has been a very infrequent recurring issue for me).... Then the idle speed dropped off and the car almost stalled. Then I got ENGINE FAILSAFE MODE appearing (ASC/TRAC NOT AVAILABLE are still there also) The Check Engine Light was NOT on during all of this.

I moved off from the light and even with my foot to the floor the car was only capable of doing 5 mph. I pulled off the road and switched off. Opened the bonnet, looked around for anything obvious (loose wires, loose tubes, etc) Couldn't see anything. Started the car back up and everything was ok again.

Car then ran fine all day. I pulled the codes when I got home tonight and apart from P1000 which we don't worry about, the only other code I got was P1642. From researching, I get 2 conflicting answers. One option is Fuel Pump, the other is CAN failure. Can someone confirm which is the correct answer ?

I have worked out that I only get ASC/TRAC NOT AVAILABLE when I have someone sitting in the back of the car (strange but 100% correlated so far) so I'm going to have a good look at the healboard fuse boxes tomorrow night and see if there is anything amiss in there as thats the only thing I can think of that would lead to a correlation with back seat passengers. My understanding is that the CAN isn't a module, it's a seperate circuit system that connects various modules together and lets them communicate. I'm leaning towards some kind of connection fault, but I'm guessing.

Any insights would be appreciated.

Incidentally one of my passengers runs 2 (yes 2) Alfa Romeos and as my XJS is still in pieces recovering from a Marelli cat fire I was temporarily without Jaguar transport today, much to his merriment, as both his Alfas are currently running, so I need the Forum team to focus on this to help me save face :-)

 

I show it as CAN circuit malfunction.

When detected it limits throttle to 30% and inhibts cruise control.

Possible causes
CAN short circuit fault
Control module failure

 

Hi SARC,

I don't have any hard facts to drop...my opinion is that you should have the car scanned for other DTC's with a proprietary Jaguar scanner (WDS or IDS) to see if other fault codes are stored. I believe the P1642 code is just as likely to be the effect of another fault, as opposed to being an indicator of the cause.

 

Hi JtO

Makes sense. I'll drop by my man on the way home today. He has a WDS.

Hi Ron

Thanks for the info. I saw more hits for the CAN circuit malfunction than for the fuel pump. It certainly does limit the throttle anyway.

 

That's sort of where I am leaning, one example of the symptoms you described is a throttle position sensor/ throttle body fault which caused the CAN circuit interruption as a result.

 

I believe P-1642 is frequently an artifact of the scanner connecting to the communication system. As to the original problem, my '02 XJ8 has done that twice in 155,000 miles, two years between occurances. I have no idea about the cause.

 

Ok, so here is a longshot....The number nine fuse (30 amp) in the smaller underhood fuse block. Once, while the engine was running, I started to remove that fuse. Don't ask me why. As I pulled it out, the engine began to stumble. I pushed it right back in, and removed my fingerprints. I walked away and looked cool. But when I got back into the car a minute later, I got the same warning you did, without an engine light, and the engine was in failsafe mode. I turned the car off, and let it sit. I turned it on again, and it was still screwed up. I started it again, and pulled the same code you did. Never got a light. It works fine now.....

...so maybe you could look there.....

 

Hi John

Thanks for that, I'll have a look at the fuse in the morning (just spent to whole evening putting the XJS back together after its cat fire so I've had enough of Jaguars for one evening!)

Hi Sparkenzap

Interesting point. I checked the wiring diagram and found out a bit more about what the CAN actually is....

CAN is Controller Area Network, and appears to consist of 2 wires (Green and Yellow) which go to all of the following modules :

1) Data Link Connector --> so makes sense what you said about the code reader itself creating the code
2) Instrument pack
3) Gear Selector Illumination Module
4) Vehicle Speed Interface Module
5) Engine Control Module
6) Transmission Control Module

and finally

7) ABS / TRAC control module.

I think based on the symptoms its at least worthwhile for me to have a look at the wiring around the ABS / TRAC control module, especially the CAN wires. We'll see.

Actually when you start to look at the circuit diagrams and the complexity of a modern Jaguar, it's a miracle they ever work at all :-)

 

There was a ECM re-flash for your vehicle, detailed in TSB303-49.

If performed, there should be a sticker bearing that number which was placed adjacent to your left hood hinge.

If not, that's another point to raise with the Dealership service department when you bring the car in to have it scanned for other trouble codes.

 

Well, I had a look at the wiring around the ASC/TRAC control unit and all looks ok. Had an assistant wiggle things while the car was running and no faults appeared.

I took out the fuse recommended by John and cleaned the contacts.

I don't have the sticker under the hood. I have alldatadiy.com subscription and I can see the TSB you mentioned JtO so I'll bring that up the next time the car is in.

So for now this will be marked up as "Strange Gremlin" and filed :-)

 

i have this problem child car it has misfires on 3 and 5 and the battery light comes on the tach and coolant sensor are inop and have a cod 1642. I have replaced coils, plugs, and battery. Checked charging system and is charging. Im at a loss for this bought this car and had for a week and now this.

 

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Just had P1642 this morning on the '01 XJ8. Not the first time though. I can relate to Parkenzap comment : "I believe P-1642 is frequently an artifact of the scanner connecting to the communication system" - this P1642 seems to always happen after an issue related to connecting to my reader. MIL comes on and no other codes than P1000 and P1642. The car drives perfectly fine with the P1642, but I end up erasing the codes of course. My problem is that I am due an inspection and I frequently check the status of the cycles... and every now and then this f'up happens when connecting the reader and gotta clear the code - therefore needing to go through all the cycles again (which seem to take forever...).

 

just because your light is on does not mean that you cannot pass inspetion. You are allowed certian fails and can still pass.

In nc if whatever repair is needed is over $200.oo you can get a waiver and get your inspection anywhow....


I got this code a few times.. it was from my scanner.

I have a cheap cen tec scanner just for engine codes. i bought it because the jag was ALWAYS throwing out codes (knock sensors) and i wanted to check to make sure there was no new problem.

A few times after checking and clearing the knock sensor code i would get trac/brake gearbox failure message on start up and get the 1642 code..

have since replaced the knock sensors, and now never a code... and car runs WAY better...

 

Just wondering if you ever got a remedy to your situation. I am in the exact same predicament with my 2000 xj8.

 

Which predicament are you in? That you frequently plug in your scanner and get p1642, or some version of this story?

 

Specifically, I was getting the p1000 and p1642 codes, preventing me from getting a state inspection (Texas). I recently cleared the codes, but now I'm unable to get inspected due to the "not ready" codes (because I cleared them). Inspection guy said I have to drive until the ECM resets. I am going to try to get a waiver from the state. I'll report how that turns out.

 

Post #29 in this thread has the MY2002 drive cycle. It is pretty close to the earlier one that applies ro your car.

https://www.jaguarforums.com/forum/x...-115863/page2/

 

My car is a 1999 XK8 with, beleve it or not, 398,000 miles. i have woned this car for 16 years starting at 35,000 miles when i bought her. Living in So. Cal i do lots, and lots of drving. this is my daily cruser. I also own an '89 Lotus Esprit and Ducati for weekend fun. Anyway, i have seen some dicussion about P code P1642 which is why i jumped in but, my car runs fine. i cleard the code twice and it re apears about a week later. Any other thoughts on this matter?

Thanks
Greg