hey all

I have a 1998 jaguar xjr 4.0 supercharged Canada version. I have just lost all headlights and tail lights as well as key fob stopped working all suddenly.

I am throwing the following codes. Can someone please shine some light on these?

p1787
p1000
p1646
p1797

thanks so much

 

p1000 is the usual system checks not completed - not a problem, won't go away til other issues are fixed
p1797 - can tcm/ecm circuit failure. I have the description in a thread I posted recently https://www.jaguarforums.com/forum/x...mptoms-176735/

p1787 - ??? maybe another transmission code, didn't see it in the XJR transmission list

p1646 - fuel pump 2 relay malfunction

if you're losing power in multiple systems I'd be checking the power distribution wiring for faults at those points, esp areas where faulty systems meet at a common connection, like a fuse box

 

hey thanks for your reply nilanium

I am in limp mode I think. The gauge cluster said "restricted performance". I'm also stuck in valet mode for some weird reason.

I think the main problem is the p1797. I have read your post regarding it. I cant even erase the code my scan tool wont allow it and its top of the line snap on one.

How can I test my CAN wiring for faults? From what I gather CAN wiring is communication between the cluster shiftier tcm and ecu. Im going to check out that transmission plug first and see if anyone of the wires are broken. Will I know just by looking at them or do i need to completely remove it?

My local stupid dealer ship wants 180 bucks to pull codes for the CAN network to attempt to pinpoint the problem

 

If I remember correctly, the CAN system has a 120 ohm resistor across each "end" of the network. So, with the battery unplugged, you could unplug a connector and check resistance between the two CAN communication wires - a reading of 60 ohms is good, a reading of 120 ohms means you have a break somewhere, and a reading of very high resistance means you have multiple breaks or no conductivity. A reading of 0 means there is a short somewhere.

I'd triple check all this before doing that test, I don't remember that too clearly so it may have been for another car, different system, or whatever. You don't want to brick your computer modules, etc. doing the wrong test.

The schematic for the CAN network is figure 19.1 here http://www.jagrepair.com/images/Auto.../jagxj1998.pdf

I'd probably figure out the cause of loss of power to lights and other things first before attacking the P1797 - they could both have the same root cause.

 

Hi Bigredjaguar,

Here are some links to service documents that may be helpful. The DTC Summaries manuals give possible causes of each code, and the Electrical Guide shows all the wiring schematics.

Jaguar AJ27 DTC Summaries Manual

Jaguar W5A-580 Transmission Control System DTC Summaries

Jaguar XJ Electrical Guide 1998

P1646 indicates a problem with the control of the Bank 1/A upstream O2 sensor.

I don't see P1787 in the Jaguar documents either. Is it possible it had a B, C or U prefix instead of a P?

Please keep us informed.

Cheers,

Don

 

Yes sorry I may have typed them in wrong. these are my codes.

p1797
p1000
p1646
p1797

I find it weird that p1797 is in this 2x's it said one is a pending code.

I have no idea where to start. Do you guys think I should replace that transmission connector? I don't have any trans fluid leak but I wonder if its leaking internal or something.

I don't see any diagram for the network in the wiring diagram maybe I'm blind.

I did just finish replacing the alternator this is the second time I have had to install a new one due to the part inside of it burning up.

I have had the bpm slcm ecu looked at by electrical repair shop all is fine with the modules. Im looking at different places on the power distribution looks real simple. just comes from the alternator right back to the battery and around the car to all the fuse boxes. I have checked all fuses over 5x now. nothing is blown.

 

I'd fix the O2 sensor first.

 

On a 98 XJR P1646 should be the secondary fuel pump solenoid, not the upstream O2 sensor.

 

Thanks, RJ. I forgot the XJR wasn't updated to the AJ27 till 2000.

Bigredjaguar, here's the link to a scan of the DTC Summaries manual you need:

Jaguar AJ26 DTC Summaries 1997-1999

Cheers,

Don

 

If the lights still aren't working, and the power distribution looks good, then I'd try working backwards, or I guess top-down? Start at the symptom (no running lights), trace those backwards in the electrical guide to the first common point (either relays or control modules, I don't remember), then keep working backwards towards power distribution until you find the fault.

If the lights and other issues are CAN or SCP controlled, there's some very useful charts at the very end of the Electrical Guide that explain which module sends/receives what within each network.

 

I have been tracking for hours. I did find out that the start b+ wiring going to the alternator is corroded to hell. I am going to attempt to clean that up. I was wondering is this the plug that the tsb is talking about?

The Mercedes replacement plug on amazon is a whooping like 13 bucks. I am tempted to swap it out just for the hell of it.