Disco 3 (LR3) Unusual intermittent park brake/EPB fault. Canbus?

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scrappyloz

scrappyloz

Active Member
Posts
398
Location
Hereford,Herefordshire
Hi im wondering if someone can help me with a very unusual fault im having with my discovery 3.

I know my way around the discovery 3 very well but this is a fault i have never come across before.

Every time i start my discovery 3 after it has been sat for a while the red and yellow P lights are on. The only way to release it is to start the car (have to start cannot just turn ignition on) then turn the car off and then turn the ignition on whilst pushing the park button down.
The parking brake will then release and then works perfectly. with no further fault.

I can also turn the car off and come back to the car in a short while and the park brake will still be fine.
If i leave the car for around 30 minutes or longer the fault reappears.

I code read the modules and the faults i have coming back seem to refer to a canbus fault. I did have water ingress to the vehicle from bad sunroof drains, which i have now fixed and also dried the entire car but the loom was wet from the water ingress. Are there splices for the canbus in the loom the runs down the door sills

PARK BRAKE MODULE
C1A00-00 CONTROL MODULE
U0101-87 LOST COMMUNICATION WITH VEHICLE DYNAMICS MODULE
U0100-87 LOST COMMUNICATION WITH ECM/POWER CONTROL MODULE
U0155-87 LOST COMMUNICATION WITH INSTRUMENT CLUSTER MODULE
U0122-87 LOST COMMUNICATION WITH VEHICLE DYNAMICS CONTROL MODULE

INSTRUMENT CLUSTER
U0001-88 HIGH SPEED CAN COMMUNTICATION BUS
U0010-88 LOW SPEED CAN COMMUNICATION BUS
U0159-87 LOST COMMUNICATION WITH PARKING ASSIST MODULE

TRANSMISSION
U0155-87 LOST COMMUNICATION WITH INSTRUMENT CLUSTER MODULE
U0128-87 LOST COMMUNICATION WITH PARK BRAKE MODULE

ECM/ECU
U0128-87 LOST COMMUNICATION WITH PARK BRAKE MODULE
 
Is the mechanical side of the epb, clean and lubed and functioning properly? Wiring fault is next place to look, as in connectors, pins etc
 
Hi yes it works perfectly when the car is turned off and on. I checked all three plugs behind the passenger rear arch and all were fine with no corrosion or damaged wires etc.

i also checked the ecu, tcm and large connectors near and behind the battery and they were all fine as well. Do you know if the can bus lines are spliced anywhere?
 
Hi Scrappy does everything else work or do you have other faults?
Have seen epb fail if gear position indicator not working.
Is the battery in top condition as low voltage after start up can cause epb and other faults
 
adrian hogg said:
Hi Scrappy does everything else work or do you have other faults?
Have seen epb fail if gear position indicator not working.
Is the battery in top condition as low voltage after start up can cause epb and other faults
Click to expand...


The battery is perfect with no issues at all.
Everything else works fine
when you say the gear position indicator do you mean on the cluster or the lights around the selector?
 
I think I would be checking all power supplies and earths to ecm if you have a wiring diagram.
Have had random epb faults on a Subaru and found one feed to ecm missing even though it was a fuse blown in signal wire from glowplugs to ecm. the car kept throwing random epb faults.
 
scrappyloz said:
The battery is perfect with no issues at all.
Click to expand...

Have you done a voltage drop test on the battery while the engine is cranking? If the battery voltage is to low or fluctuating lots during cranking, a whole host of fault codes are generated.
 
Hi the battery is brand new (was my first thought). The fault doesnt arise from cranking. If i go out to the car and turn on the ignition only without cranking the fault is already there. I have to start the car and switch it back off for the problem to go away
 
I’d do a voltage drop test on the feed to the eps module as there’s a splice in the rear chassis which can corrode and cause these issues.

The main cause of those faults in my opinion is the C1A00 fault in the EPB so I’d be looking at the powers/grounds and comms lines to that first
 
scrappyloz said:
Hi sorry what is the eps module?
Click to expand...


Suspension in off road height and shine a torch over the top of the rear tyres to just abiove the rear diff area and you can see the epb module, Iirc you have to remove the spare tyre to gain access from underneath?
 
Right time for an update. Had a look today and still haven't resolved the fault.

I did find however:
1. If i turn the ignition on and wait for the dash lights to go out I will find than the yellow P light stays illuminated (indicates the fault im having). If i turn the ignition off and on again (1 or 2 times) the yellow light will go off and the park brake works fine.

2 when the yellow P light is illuminated on the dash and i do a system scan, the EPB module is not found on the code reader. If i code scan when the yellow is off the EPB module is found.

Surely this means the module is not waking up and communicating due to either voltage or can bus issues due to the fact that cycling the ignition a few times sorts the problem

I will be checking all the wiring tomorrow according to
http://rave.stringsandints.com/LRL183853501(LR3-Wiring).pdf

I know i will be looking at the two constant lives
Ignition live and key in live
Grounds x2

If they all check out ok it will be the canbus which will be the next port of call.

I have a question regarding the 2x constant 12v feeds that supply the epb module.
The yellow and green wire goes to connector c2528-c2527 (connector located in passenger front arch behind arch liner) I found that my connector has been bypassed in the past but has a constant 12v feed where it has been bypassed. Looking a the wiring diagram i see the wire splits at SJ406 and then goes to the parking module.

Does anyone know where this splice is or how this wire gets to the epb as it does not go through the connectors behind the passenger rear wheel

Thanks
 
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