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Electronic Parking Brake - S Type 2.7 2007


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Hi, This is not an appeal for help (although any additional knowledge is always gratefully received) but more of a guide to my current problem and how I've gone about fixing it so far in the hope that it may prove helpful for other S Type owners.

My car is a 2007 S Type 2.7 diesel. Automatic. 131k miles

Last year (Jan-Feb 2020) I had to replace the Electronic Parking Brake (EPB) because the cable from the actuator had corroded and snapped. This meant that the EPB could not be applied.

This time (Jan 2021) it is the opposite, the EPB was stuck on and would not release. My Jaguar/Landrover specific reader displayed continuing code (DTC C1785 "EPB MOTOR OUTPUT OPEN CIRCUIT."

My Battery is 2 years old and is 105Ah 850CCA reading 12.55volts. As I don't use the car often and only for trips of around 6 miles each way, I charged the battery for several hours. When I took it off charge its reading was 12.73 volts and the EPB still would not release.

I then shimmied under the car to manually inspect the brake cables from the actuator and to each rear wheel. All were ok and very taught.

I then tried the EPB release/reset advice on this forum of removing the two multi wiring plugs from the EPB control Module in the boot (on the sidewall of the boot under the cover, just above the battery). I removed these plugs with the car running and with the car ignition off but the EPB was still on. I disconnected the battery for 15 minutes and reconnected it but still the EPB was on.

I also tried to drive the car forward and backward to release the EPB bu it did not release.

I finally removed the left (smaller) multi wire plug, and connected the two thick wires (a green/white and a red/white) direct to the battery. The first time I heard the EPB actuator clicking each time I made the connection so I reversed the wires to the battery and the EPB released.

Now, here is my thought process......The EPB Contol Module receives messages from the switch in the centre console area and also when you drive away with the EPB on,( ie the EPB releases automatically).

1. If the actuator works when connected direct from the battery, the actuator cannot be faulty.

2. If the EPB did not release by the switch or by driving the car forward/backward, the fault must be in the Control Module itself.

 

I have now ordered a (used) replacement EPB Module. The replacement has all the same numbers as my original EP module, including the REV letter (In my case "E")

I will update this post once I have fitted the replacement EPB Module next week. Fingers crossed!!!!!!

 

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Well, I replaced the EPB Module and it initially generated several additional fault codes within my Icarsoft i930 reader but once those fault codes were cleared, the module behaved in the same way as the original module  - ie EPB applied the park brakes and does not release. Fault code C1785 returned. I now need to look elsewhere.

A service bulletin relating to the EPB has a section for checking the EPB motor re fault code C1785.

It refers to checking the ohm resistance of two pins (pin 1 and pin 6) of the connector CA269,  a grey coloured connector situated near the rear suspension subframe. 

If (when I manage to find a check these readings) the reading are incorrect, it appears I will have to replace the EPB actuator for a second time in 12 months.

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Problem solved.....or should I say 'sorted' as I'm not entirely sure what I did.

 

Let me first say that I have an icarsoft i930 code reader (a must for Jag owners I would suggest - it has saved me a fortune over the last few years)

 

I had already replaced the actuator in Feb 2020 with a used unit. 

When this most recent fault C1785 occurred a week or so ago, I purchased a new Bosch S5 battery and a replacement (used) EPB Module that had the corresponding codes and revision "E" the same as mine Neither of these steps altered the C1785 DTC and the fault remained.

Connecting the actuator direct to the battery showed that it worked both ways.

 

This morning I removed all the objects, tools and bottles of water and antifreeze/water mix. The reason for the water and antifreeze mix is that in October 2020 I had to replace the heater motor under the front of the car and had previously been loosing coolant.

The spare wheel well was quite wet in places so I dried everything out.

 

I then began to check wires into and out of the two multi connectors to the EPB Module. I pushed the wires into the connectors from the back to make sure they were seated properly but did not notice any obviously loose.

 

I tried the replacement Module again and then jumped in the car and switched on the ignition. The dash warning had gone but just showed the usual 'press brake and park brake' message. After doing that, the park brake came on without a problem and now works fine.

 

Was it wiring or damp? Who knows. I'm just so glad it's sorted.

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