EDIT: Resolved - clearing out the code and doing a neg-to-positive seems to have cleared everything up and it hasn't returned. Thanks!

So, my 02 XJR seems to be acting up.

CEL light illuminated, but otherwise the car is running flawlessly. No apparent change in operation whatsoever. Pulling codes gives me P1601 and P1111.

A quick search seems to say p1601 is an ECM/TCM communication error - but wouldn't that end up giving me some indication in the way the car is driving? I'd think it would have engaged some kind of limp-home mode, but, nothing. Bizarre...

Any thoughts on what steps I aught to take to figure out what is going on with my baby? I'd like to exhaust the basics before I take it to a shop and have them tell me it needs a whole new "insert 1000$ part here". I'm proficient in my own repairs but I haven't spent much time under the hood of my jag just yet. Anyone dealt with this particular code before? How did you resolve the issue?

Tried finding answers everywhere I could. I found plenty of info from people who had the issue, but nothing about people who -solved- the issue (and most of the threads I've read on this issue involved an obvious drivability issue piggybacking with this code, so it doesn't seem to be the same on my car).

Any help is greatly appreciated.

 

The first thing to do is a hard reset and see if the code repeats. Disconnect the neg. battery cable and touch it to the positive post for about 30 sec., then reconnect. The P1000 code will appear telling you internal system checks are incomplete and the idle and shifts will be a bit funny until the systems relearn. Then the P1000 will become P1111 after a few drive cycles.

If the P1601 repeats it will be time to look for problems.

 

Disconnect the negative battery cable . . . FROM THE BATTERY . . . and touch it to the positive post . . . .

 

Grab JTIS, look up codes (very carefully for any that start P1 because then they depend on make,model,year), see when they flag & all known causes. Many codes flag if present twice, the fault doesn't have to be there all the time.

 

I'll give the batt terminal a shot. I actually disconnected the battery entirely overnight thinking I'd clear things that way (it's how I usually clear lights on previous vehicles I've owned) and it didn't help despite 12+ hours off power. I'll do the touching neg to pos and see what happens and report back later today, if that doesn't work, it'll be time to dig a little deeper.

 

Well, that fixed it...

Went ahead and tried the battery touch, but that didn't seem to want to reset the light. I just went ahead and reset it with my scan tool and everything seems kosher after a nice long drive and a few drive cycles.

We'll see if the light comes back. I wonder why it popped up in the first place?

Anyway, thanks, I was really hoping it wasn't something bigger. I'll be back if it pops back up .

 

A weak battery, either age or just lack of use can result in odd codes. Stop at a parts store and ask them to load test it. Even a dodgy power or ground connection could be at fault. Glad to hear the scan tool reset worked, I should have suggested that first.

 

Hi xjrmgeddon,

If the code recurs, it might be worth cleaning the engine bay and firewall ground studs and associated wire eyelet terminals. Loose or corroded ground points can trigger hard-to-diagnose gremlins. The ECM and TCM both use the "EMS LH Ground" stud on the left inner fender for their logic ground point, and the ECM also uses the ground stud on the firewall behind the cylinder head (EMS Bulkhead Ground Stud EM16).

Also, TPS issues can trigger ECM/TCM related codes, so it might be worth cleaning the electrical connector for the TPS.

Cheers,

Don

 

Yeah, I would have done it first and foremost but since this is my first jag (well, technically second if you count owning the first one for 6 days before I totaled it), I just wanted to see if anyone had any insight before I got started. I was at work, so there wasn't much I could do except ask for help.

Anyway, I have some great advice here and I think I'll give her a going-over since I'm already planning a bit of work this weekend. She feels like she could use a new set of plugs and an oil change, so I'll be under the hood. Good times.