I have a 4.0 ltr Daimler hearse built on the X308. Intermittently, it will flash up with the warnings - ASC off, ABS off and Gearbox fault following which it goes into Failsafe mode at 1200 RPM. We replaced the throttle-body, then the ECU, then replaced the alternator, none of which seemed to cure the problem. I did suspect that it was the level of charge going into the battery as the vehicle tends to do short journeys with a fair bit of stopping and starting (and lets face it we don't do much of a speed), plus heavy loading on the battery (aircon, lights, etc.). Considering that the battery may not be holding its charge as much as is necessary, despite the car fires up instantly etc. I have even put a new battery on with higher Ampage. The intermittent problem persists though! Any suggestions would be much appreciated.

 

Could it be an issue with the J gate shift sensors? If I remember right those sensors can trigger a gearbox fault if the output isn't what is expected. Shift cable tension?

The ABS/ASC may or may not be unrelated faults. Are there any OBD codes stored? Which year car is it?

 

It is a 2003 but given that these are coachbuilt, it is the X308 platform, so probably last of the x308 line. The ASC, ABS and gearbox fault warnings we think are spurious, as the car can go miles in between the problem occurring. The OBD code comes up as throttle-body but that was the first thing we replaced, but its till comes up as throttle-body.

 

The Alternator and Battery might be happy but there are connections to cables and power 'studs' that might be 'suspect'. Modules on the CAN bus need a steady power supply and poor connections can cause problems.

Since the vehicle is not an ordinary body I would guess that many of the TSBs might not apply. Sharing a platform is not the same as factory built coachwork.

Your problem does seem CAN bus related. The INST PK, Gear Selector, ECM, TCM and ABS are on that bus in that order. Monitoring module parameters seems unlikely while transporting grieving passengers.

I hate intermittent faults as they are difficult to reproduce.

Keep us up to date on any progress.

bob

 

Good suggestions Bob. After it had the issue yesterday, I put the battery maintainer charger on it overnight and it has been fine this morning. I do think it is very sensitive to battery level, and bearing in mind, it's intermittent usage and the way it is driven, I think I will just stick the maintainer on it when it is the garage, and see how that works. When it is next of the road for maintenance I will follow through on your suggestions though, thanks.
David

 

Hi David,

Welcome to the Jaguar Forums! It's great to have you with us.

As Bob suggested your bespoke hearse will have some differences compared to the regular production saloons, but the major electrical components and connections should be similar (though perhaps not always in the same location as on a saloon).

Here's a link to the latest X308 Electrical Guide available at jagrepair.com, courtesy of our member Gus:

2001 XJ X308 Electrical Guide

nilanium asked about any stored diagnostic trouble codes (DTCs) - that is a very good question. Have you scanned for codes that could help narrow down the diagnosis?

Intermittent problems like this are often due to the cumulative effects of more than one smaller problem. If you have no codes, some things I can think of that could possibly help are the following, in this approximate order:

1. Physically clean all four wheel speed sensors and their associated harness electrical connectors.

2. Check the large electrical connector at the ABS/Traction Control module for any signs of water ingress or corrosion and clean as necessary using a small wire brush and zero-residue electrical contact cleaner (disconnect the battery negative cable before cleaning the connector in case any pins carry battery power). Also clean the smaller 2-wire power supply electrical connector.

3. While you have the large connector disconnected, use an ohmmeter to check the resistance of the circuits for each wheel speed sensor. The pins to check are shown in the chart at the link below, courtesy of Gus and his jagrepair.com website. Note that Gus states the resistance of each wheel speed sensor circuit should be 2.0-2.2 Kohms, but on an X100 I recently measured the resistance was only around 1.4-1.5 Kohms. You may measure a slightly higher resistance at your rear sensors if the wheelbase of your hearse was extended. If a circuit measures a lot lower than the others it may be shorted or the sensor may be faulty: measure the sensor directly. If it measures a lot higher or open, a wire may be broken or the sensor may be faulty: measure the sensor directly.

X100/X308 ABS Diagnostics

4. While you are testing the resistance of each wheel speed sensor, manually flex and manipulate the wiring harness near the sensor and watch the meter for any signs of an intermittent break in the wiring.

5. A very common problem on the X308/X100 is starved, cold or cracked solder joints on the circuit board inside the ABS/Traction Control Module, which can often be repaired by reflowing the solder and supplementing with new solder as necessary. To remove the control module from the ABS modulator see the instructions here:

ABS/Traction Control Module Removal

To access the circuit board, the document at the link below shows a method of drilling a hole in the module cover:

ABS Module Repair

However, I recommend carefully removing the entire cover because I have found that the two large power supply pins are not the only ones that can have bad solder. See the photos in this document:

ABS Sensors & Module Repair

6. Clean all the battery power connections, starting at the battery terminals and battery ground wire connection to the body and the high power protection module, and work your way forward to the engine bay to include the false bulkhead connector, alternator, starter, and engine ground strap (both ends).

7. Clean all ground points associated with the ABS/Traction Control system (see the schematic in the Electrical Guide).

That should be a good start.

Please keep us informed.

Cheers,

Don

 

Some really good pointers there and many thanks Don. The only worthwhile code points to throttle-body but since that was replaced first, we have ruled that out now. Sometimes we get no codes at all! I put a maintenance charger on it overnight because it was being used for a funeral today. Fired up first thing this morning and took it out for a blast, which it rarely gets. Whizzing it around the local country lanes is always an interesting and fun experience, given that it is over 21 foot long and about 18 inches higher than a standard car in the cabin, and the weight distribution with all the glass in it really hits the handling! However, the run will have done it good and no sign of the problem as it flew around. Hoping it is an electrical power issue as it certainly is a major feature of these things in terms of setting off the spurious warnings. However, I need to set some time aside to go through the check-list that you have kindly given Don. Though we have already done some of them, there is still plenty to go at!

I will keep you updated as we progress.

Cheers,
David

 

Used to be known as "an Italian Tune-up" and very effective. Nowadays that's probably also very effective in upsetting the PC zealots!

Given the general combination of slow speed, short runs and high electrical load, I'd be surprised if keeping it on a battery tender doesn't resolve the issues.

I wouldn't like to handle the back end stepping out on a fast corner and a narrow road in a 21 ft long top heavy Jaguar hearse.

Graham

 

Hi Graham,

Yeah, the switch from under-steer to over-steer is an interesting transition! The matching limo handles a bit better but since it is set up with a higher ride height than a standard car, it isn't exactly an XK. For proper driving, I will stick to my XJ8 4.2 Sovereign.

We will see how things go with the maintainer charge.

David