So I've been having some problems lately with my Jaguar. A 2004 XJ8 X350. At first the car was sitting then tried to start on its own. The fan would start and then it would crank without the key in it. I then based on research decided to look at the ecm because after that occurring, the dreaded "Engine Systems Faults" error came up, putting it in limp mode. I then took out the ecm and found it was very wet, had algae growing in it and was corroded. Also on a side note, using a phone app, the car threw at least 15 fault codes and kept blowing the ignition coils fuse. I sent out the ecm to be supposedly repaired. I reinstalled it and found the same issue occurring. It did reduce the number of codes and the fuse now doesn't blow. My current codes are P0560 and P1251. The problem is that I went in and tested the electrics on the throttle position sensor and resulted with no faulty wiring.

The other thing to note is the throttle motor is not actuating. Weather or not this is due to it being in limp mode, I'm not sure.




At this point in time I'm at a loss for ideas and need help, thank you.

 

P0560 - system voltage - https://www.obd-codes.com/p0560
P1251 - throttle motor relay malfunction - https://www.obd-codes.com/jaguar

So I would look at that relay and inspect additional wiring & connectors for additional problems.

 

Hi KJ4YXY,

I'm sorry to hear of your trouble, but you're not the first to have a water-contaminated ECM. I assume that before you reinstalled the ECM you cleaned the harness electrical connector with zero-residue electrical contact cleaner spray and cleaned the water drain below the electrical connector so water won't pool there again?

The Jaguar definitions and possible causes of fault codes often differ from the generic ones, so it's best to refer to the Jaguar Diagnostic Trouble Codes Summaries Guide, which you can download at this link:

Jaguar X350 DTC Summaries Guide

In reading the possible causes of both codes, one thought occurs to me: corrosion on the ground point referenced by the ECM could reduce the battery voltage/current metered by the ECM (one of the possible causes of P0560), and would be consistent with an ECM ground fault (one of the possible causes of P1251). Off the top of my head, I believe the primary ground used by the ECM is located on the right inner fender not far from the firewall/bulkhead. Given how much moisture you had in the area, it would be worth thoroughly cleaning that ground point, and while you're at it, you might as well clean the other engine-bay grounds, including the three behind the headlamps. The ground locations are given in the Electrical Guide, which you can download here:

2004 Jaguar X350 Electrical Guide

Below is a link to some info on cleaning the ground points. You cannot trust a visual inspection to tell you that a ground is clean. Aluminum oxide forms on the threaded stud, aluminum eyelet or ring terminals, and aluminum nuts. The layer of aluminum oxide is only about 4 nanometers thick, so it appears as a thin, whitish discoloration, but since it is an electrical insulator, the resistance it adds to circuits can cause all sorts of hard-to-diagnose electrical gremlins. Pay close attention to the fact that the torque specification for the nuts is a very low 6.5 ft. lbs., or just a little over hand tight. Lots of owners have snapped threaded studs off the body by overtightening a nut.

Grounds / Earths Near the Headlights

If cleaning the grounds doesn't resolve the DTCs, investigate the other possible causes given in the DTC Summaries Guide.

Please keep us informed.

Cheers,

Don