doesn't look so easy to access

Hi folks. 2002 STR has thrown a code yesterday (C1786) that states motor output battery - short circuit to ground.

I had this some time ago as the previous owner had the car stored for a very long time. My remedy to investigate was to disconnect and reconnect the Parking Brake unit in the boot/trunk and also take off both park brake calipers, clean em including sliders and then replace...both of these tasks meant it was a success as I had no dtc's after that. Have done 8000 miles since without problem. BUT now its back same code as before.

When it appeared yesterday i cleared the C1786 code and set off on my trip.... remembered to hold off the park brake when i came to park up.
When i got back to base later, I then took off both wheels to investigate and I re-cleaned the sliders on the park brake calipers and replaced. Didn't seem excessively dirty. Still have the code though.

Has anyone had this issue and if so what should i look at next...Cables to actuator arm, Motor?

Access to the motor or anything around there looks like a challenge. I don't want to drop the sub-frame if i can avoid it.

Thanks in advance.

 

It seems it's an electrical short so I don't see how it can be the non-electrical cables (unless an electrical part is shorted to one, which is not so likely bearing in mind all the other things available).

I don't recall postings before but try Search using the code.

 

OK Thanks JagV8. on further search not very much showing but looking at the manual suggests pinpoint test D:

I'm curious to see if i can get to the motor...Im assuming that it cant be seen from the top (access panel in the boot/trunk) ?

 

Have you seen this? Lots of spurious EPB faults can be caused by a marginal battery. Something to consider before digging too deep elsewhere:


https://www.jaguarforums.com/forum/s...attery-193787/

 

Thanks Karl. Was thinking maybe it could be that but then I saw the OBD readout on my dash command and it read 13.4v (never gets above that) which in my mind is lower than should be when engine running. That set me off that the alternator is not doing its job which may ring true as it was drenched in engine oil that was running down from the leaking cam covers - now fixed

I'll figure on getting it hooked up to a tester tomorrow.

 

On a 2003+ car, you should see around 14.5v for the first few minutes, and then slowly dropping to about 13.5v. Your alternator may be fine.

The main gist is not the voltage while running, but before start. Low prestart voltage seems to be what sets the random EPB faults. You’d think the computer would be smart enough to realize this, but apparently not.

One troubleshooting method is to hook up the battery to a charger each night for a week or so. This makes sure the prestart voltage is good. If the EPB now behaves, then you know you’re on the right track. Doesn’t cost anything to try, other than a little bit of your time.

 

almost all the stype PB faults are caused by a low cca (cold cranking amps) during cranking causing a momentary low voltage the module does not like. I cannot count how many times these problems come in after being at indie shops with lots of new parts and they gave up and told customer to go to dealer. Customers didn't like the response of you need a new battery. Well I would have told you that BEFORE you spent all that money but hey we're too expensive right

 

+1

I suppose the state of that electronic module's art (about 20 years ago when designed) just was not what we today would expect. C'est la vie...

As is said often on here - battery is #1 suspect.

 

Update: I believe i have fixed it. Fingers Crossed.
Thanks Karl, Brutal, JagV8...good advice as ever.
Yesterday afternoon i set about the condition of the battery that i know has been on the car for only 2 years as I have all the matched receipts from the previous owner.
I charged up that battery and had a reading of 12.9v when i came to reconnect a couple of hours ago. I reconnected the leads and went about the normal operation of starting the car.
After resetting the park brake the fault was still there.

So OK, what next.? I thought to have a look at the other two S types that I have, one in dry dock (under repair) and the other (V6) used as a spare car. The dry dock car has a completely different module (2006) so left that alone and took at look at the other car. I found that the parking brake modules have similar codes, have the same size box, and have an equal number of pins in the connectors. So i removed it and hooked it up and hey presto the park brake fault notice instantly disappeared from the dash. I've cycled a couple of times and so far its not returned.

I am equally cautious here as i have crowed loudly before after spending a long time trying to seek a solution only for the problem (particularly electrical) to come and bite me in the ***.
I can now drive it again. I was all but ready to get underneath and look at the actuator and its connections (not too sure how easy that is without dropping the sub-frame). But that can wait for another day.

Old Unit in above pic and new unit fitted in the below pic.

 

When my previous 2005 S-Type's EPB failed back in 2015, it turned out to be a faulty park brake module. We tried several used modules to no avail. A new module with the proper revision numbers on the label was required in order to fix it. Looks like your issue was also due to a failed module....

As others have stated, a weak battery is usually the cause. But not always....

 

Thanks Jon. I read your detailed thread and sympathized with you over the pain of not having them sort it sooner.

Sometimes you are at the mercy of others who have limited knowledge when it comes to complex issues. Hats off to those involved in this forum and why it is such a good resource

These cars and most modern cars are quite complex in that very small differences can mean it works or it doesn't. Through Land Rover ownership I considered that a difficult car for a DIY'r...i did most things myself... it's actually a walk in the park by comparison. But having said all that, through other people on this forum learning/sharing the why's and wherefore's we have a very useful go to place to discuss and seek help. As I previously found with the Land Rover community, most owners would have given up if not for a common ground in the forums to share and share alike.

cheers

 

I missed my S-Type as my daily driver for a few months after I sold it in May of last year. It was a superb highway cruiser. But my trusty Outback gradually eased my mind about selling my S-Type. I have owned it for nearly four years now and other than the obligatory routine maintenance that every vehicle requires, all it has ever needed from me was one new oxygen sensor (a $50 fix). So much easier and significantly less costly to run than my S-Type was. I do not regret selling it....