I'm looking for FORUM help to solve an intermittent mystery fault on my XK8 X100 2004 MY 4.2 Litre Coupe. The vehicle is 19 years old, 113K miles and in pristine condition.

Of late the XK8 has developed a habit after, perhaps, a 30 mile journey of throwing-up a red warning light and displaying a 'Low Brake Fluid' message. In addition I get:

• The ABS light illuminated
• 'DSC not Available' message
• 'Cruise not Available' message
• The Speedo and Odometer stop functioning
• On some occasions, the Check Engine Light illuminates

The brake fluid level is perfect. Switching the ignition on and off does not reset the system or correct the faults. Leaving the vehicle overnight often resets the system and all lights disappear with speedo and cruise functions again available..... but the same problems re-occur during my next journey.

Last week I managed to get my basic OBD2 reader to download the codes.

Six codes displayed:

. P1637 - Canbus link ECM / ABS control

. C1137 - ABS module control

. C1165 (twice) - ABS sensor RH Rear

. C1175 - ABS sensor LH Rear

. P1111 - OBD2 interrogation code

I was surprised to get the C1165 and C1175 codes as I had 3 months before replaced the ABS sensors with new.

I used the code reader to erase the codes and the reader confirmed this had been successfully completed.

I drove the car for some 10 miles and all the lights and warnings systematically reappeared.

The car was left garaged and started again after 48 hours..... to my surprise all the lights and warnings had disappeared - the ABS light extinguished after travelling 100 yds. The car appears to be running perfectly with no warning lights. The only OBD2 code displaying is P1000......BUT yesterday using the car on 70 mile journey all the lights and warnings re-appeared.

Has anyone in the FORUM encountered anything similar or suggest any rectification plan?

 

What I went through was quite similar (but not exactly same).

1. If you haven't pulled the ABS computer off and drilled the hole to re-solder the two high-amp leads - do that first. JagRepair.com has a great write up (here) on how to pull the computer without disconnecting the brake lines (does require some courage to bend the attached lines a bit), as well as a 4mm & 10mm socket. Once out then follow their other article (here) on drilling a hole with a pilotless-hole-saw on a drill press. That made the biggest difference immediately for the strange ABS/Trac/CANbus errors I was getting.
2. Pull each wheel and pull each sensor. Clean the ends and make sure the teeth it observes on the hub are clean'ish too. Ohm each sensor out w/your multimeter to make sure in spec. Then check for the same ohm reading on the main ABS computer plug that you removed in the above endeavor.

 

Many thanks Rally Dog Racing.
I have already carried out the ABS sensor renewal and clean-up.
I will investigate removal of ABS Computer and re-solder of the high amp leads. I will let you know the outcome. I really appreciate you forwarding the instuction links.

 

Before carrying out any further diagnosis or repair, check the available battery voltage with the ignition in the OFF position.

Use a voltmeter across the battery terminals to determine voltage. There must be a minimum of 12.6 volts available with the engine off to have all modules function properly. If the voltmeter indicates less than 12.6 volts, charge the battery for three to five hours at 2 to 5 amps and retest. If voltage is still less than 12.6 volts, the battery is suspect and should be replaced.

Many DTCs and other instrument cluster warnings are often the result of a failing or weak battery.

 

^^ What he said....

 

Aaaaaaand, that's easier than doing the above suggested procedure. So try the easy stuff first, sure wish I could follow that advise myself sometimes. LOL The worst that could happen is your battery got a good charge. Many things on these cars are sensitive to low voltage. I use a Battery Tender (tm) occasionally on the battery that came with the car when I bought it. My .02 TM

 

Thanks NB CAT.
The battery was renewed in September 2021. When tested it shows a voltage of 12.91 across the terminals so in this case I don't think this is the problem ....but well worth a try.