Having acquired a JLR mongoose connector and the JLR SDD software to fix my own car, I have been asked to take a look at a 2006 Jaguar XJ X350 (4.2L). This is not the car in my profile, but is fairly similar. This X350 is driving normally, although recently there was an incident of the battery not charging and running out of charge; this problem has not yet been understood, this is not the issue we are concerned with at the moment, though of course we need to fix this also. For the moment we have just put in a new battery and applied a PowerMax 35A charger during diagnostics.

The initial issue is the X350 is throwing many error codes, including PCM 6 faults, TCM 2 faults, PBM 6 faults, TPM 1 fault, ASU 5 faults, ATC 2 faults, FEM (GECM) 1 fault, and REM (Rear ECU) 2 faults. All the modules seem to indicate a CAN (Control Area network) bus communication failure:

The PCM (Powertrain Control Module) faults are all marked Intermittent: U0103, U0121, U0155, U0415, P0504 & P0500. These are all CAN link related, except for P0504, however, the brake lights works fine despite P0504 being thrown.

The TCM (Transmission Control Module) faults are P1774 & P1799. Both are CAN errors, possibly due to CAN circuit open.

The PBM faults are all Permanent: C1D14, C1D15, U0001, U0121, U0155, U0401. Again, all could be caused by CAN fault.

The ABS fault is Permanent: U2521, CAN signal fault.

The ASU (Air Suspension Unit) faults are: U2521, U1900, 2302, U2518, U2523, all possibly CAN bus faults.

The ATC (Air Control Module) faults: U2521 & U2520. Both possibly CAN issues.

The FEM (GECM (I think General Electronic Control Module)) fault: B2319, not CAN exactly but circuit to ground short possible here also.

The REM (Rear ECU) faults: U3FF6 & P1235, both are a possible short to ground.

Yesterday I ran through Configure new modules for all 13 modules. Almost all had some Communication Error during configuration, but about half did indicate success at the end of the procedure. Some communication is occurring, but it is apparently intermittent.

Today I checked the Ground at the OBD and it seemed to be very close to chassis ground, resistance of 58 Ohms if I am reading my cheap DVM correctly. This should be the CAN bus ground if I am reading the wiring diagram properly. I think I should have checked the B+ line for voltage level, I will do this next.

If you saw this galaxy of issues, what would leap to mind? How would you attack this? On behalf of Eddie, the car's owner, I would like to thank you for your assistance! (I was logged out when trying to submit this; apologies in advance if this post appears twice.)

 

Isn't that 58 ohms very high?
It is well known that bad grounds can be a problem on these cars.

In particular the ones behind the headlights.

 

Ground pins 4 and 5, on the OBD connector should theoretically be zero ohms to a good chassis ground, 1 or 2 ohms at most.
CAN bus is not grounded and pins 6 and 14 should be near infinity to good chassis ground.
I would make sure that the battery indicators, in the top right of SDD screen, are both green and remain that way during programming. Slightly low voltage will fail com and programming.
The charging issue is your problem. Get the alternator working correctly first thing. These cars will light up the dash if the voltage is low!

 

pros do not use a charger while running SDD, they use a maintainer. It is much more stable.
Reconfigurations with voltage issues will eat you alive.
If running okay sort out electrical charging issue. Then obtain a maintainer for reconfig on modules. I was scared to try this with Mongoose clone and hacked software. Ended up with an iCarsoft. Not powerful enough to hurt anything.

 

DO NOT, I REPEAT DO NOT use a BATTERY MAINTAINER or BATTERY CHARGER for running diagnostics or reprogramming!

The pros use the purpose built linear or switching power supply rated for at AT LEAST 30 amperes at a constant 13.8 VDC on the diagnostic cart required to be attached to the vehicle primary 12VDC system which MUST maintain a constant 13.8 VDC or higher (full green battery signal) all during and through any diagnostic procedure, especially dealing with programming or flashing any vehicle module. A charger or maintainer are NOT RECOMMENDED as they DO NOT maintain a constant voltage needed to allow the modules to be properly diagnosed and programmed. Those diagnostic constant voltage power supplies can be built from readily available new components for less than $50 USD.

The technical reasoning behind that is in order to enter AND COMPLETE programming mode on any of the modules, the software MUST hold the programming input at a constant voltage above 13 VDC or the programming input or will fail and you can make a brick of the computer modules.

We all have seen what happens when the battery voltage drops below 12.5 volts; all sorts of error codes begin to display incorrectly, and that is also a cause of communication failures and a lot of diagnostic rabbit holes..

 

Yes, 58 ohms is inded too high. The diagnostics call for actually measuring less than 1-3 ohms IIRC using a CALIBRATED or known correct Digital Volt OHM Meter (DVOM),

There are several other ground studs on these car that fail and there is a TSB covering repair and prelacement, especially a few problem ones inside the cabin that break.
The TSB calls for REPLACING the collapasble nuts attached to the aluminum chassis by drilling individual new holes, instaling the nedw collapsable nut and adding a NEW ground wire back to another chassis ground point.

 

Can you give me some sort of information on how to find a copy of the TSB you have mentioned?

 

Do you have a pointer to instructions for building the suggested power supply?

The support engineer at PowerMax told me that many Jaguar dealers used their chargers for SDD programming, and that the amps/voltage would be maintained by their battery charger to whatever level demanded by the car during programming, even if the charger was in trickle mode at the start of the operation. But he also mentioned most of them buy the 100A charger, not the 35A unit I bought.

 

Did you manage to fix it? I'm also having those issues with mine, also code u2521. I will check the abs and other wires with an electrician because we believe rats chewed some of them.

 

58 ohms is very like CAN's 60 ohm termination - measured wrong pins maybe?