C5 Mk1 2.2Hdi Brake Failure Message

[henshaw]

I'm now getting a brake failure message occasionally when some way into a journey. I know there isn't a major problem as next day no message comes up when I start my journey and no message can come up during the journey. However this seems to be becoming a slightly more frequent occurrence. It has been said that the brake stop light switch can cause the problem. How does this cause this if this the problem? Any other ideas what can cause this message?

 

[paul.h]

An internet search suggests it could be both rear brake light bulbs may need replacing or possibly the brake light switch. You have not said the abs light is on so unlikely to be a problem with this. If the brake pads at the front are worn I think you get the Service light on. You can also check the brake fluid level and the handbrake switch.

[henshaw]

Took out 1 brake light bulb to see effects. Ignition on with no engine and with engine running produced no error message. However green light on right of multifunction display illuminated. Replaced bulb and green light unlit. When I had a rear ABS sensor failure, I didn't get braking failure message but got only ABS fault and ESP turned off/not working. The brake fluid level is ok and the brake pads are newish. What happens if there is a dodgy connection with the cables used to tell when the pads are low? (my old C5 never had these cables and also I never had a braking fault message). I'll change the stop light brake switch when the weather stops raining and see what the effect is.

[paul.h]

From your test it appears the message is due to the bulbs. I do not know what the green light is. If fitting the old bulb back has given the message again then maybe the bulb needs replacing with a new one and it may help if the one at the other side is also replaced.

 

The brake pad wear wire effectively earths the wire when the pads are worn down, so if there is a bad connection I suspect it would not give any warnings.

[henshaw]

There were NO messages. They were new bulbs put in when I was sorting out a rear ABS fault. I don't blame the bulbs.

[paul.h]

Were the new bulbs identical ones/same make ?

 

Hopefully once the brake switch has been replaced the problem will be sorted.

[henshaw]

I have just remembered that the LED on the right of the multifunction display is related to the traffic master system, though this is light is incorrectly mentioned in the handbook as being in the push button located above the drivers-side oddments pocket.

 

That removing a stop light bulb leads to an LED related to the traffic master system being lit just shows how weird the wiring on early C5s is.

[paul.h]

Sometimes bad earth connections can lead to odd electrical faults, so maybe something to check later.

[MikeLane]

Couldn't be something simple like one of the wear indicators has come adrift and occasionally earths itself as the car is driven?

That would explain the intermittency.

[henshaw]

Wouldn't this give a worn front pad warning rather than braking failure message? Still, I'll have a look at the front end later.

[henshaw]

New brake light switch, new stop lamp bulbs, unplugging and re-plugging both rear light clusters and making sure the tyre pressures are correct still leaves me with the random occurrence of the braking fault message. Anyone got any other ideas where I could look and check?

[henshaw]

Update on Braking fault message - just started winter service. Was testing and aligning windscreen and headlamp washers and wipers with the ignition on for about 10 mins and regularly using wiper/washer stalk. Engine not running, car not moving, no lights on and brake pedal not touched. Braking fault message came on. Seems to rule out stop light system. Any suggestions?

 

(Other forums suggest a faulty stop light switch could cause the braking fault message if the stop lights are on and the car is accelerating, so a slow to turn off switch could be a cause. Equally so, a dodgy stop light relay could also cause this problem. If the Haynes wiring diagram can be believed, disconnecting the plug from the stop light switch and removing the 2 stop light fuses F5 and F17 in the BSI unit should isolate the stop lights and remove the problem)

 

Seems like I'm going to have to shell a sum of money to get a diagnostic test done to see if it can trace the problem.

[henshaw]

My local garage used a tester and this pointed to the ABS pump unit. I have taken all the plugs and sockets out getting to the large plug on the control part of the ABS pump, cleaned them all and used contact lube as recommended and given the main hydraulic actuator a thump with a hammer to see if it releases sticky valves (as recommended on another forum). The problem still remains. To my mind, the fact that it is random and it doesn't appear until miles after start up and can occur when travelling and not touching brakes points to an electrical weevil.

Any other ideas as to where to look and is there any other odd function that could cause the fault. I'd hate to remove my ABS pump unit for refurbishment only to find the fault persists and something else caused the problem.

[paul.h]

The weather people are predicting snow this weekend so if you have any try the car brakes to see if the abs works since it should give the pump and valves a workout without using diagnostic equipment.

[henshaw]

Still not sorted. The messages always come up in the order brake failure, ESP not working ABS not working. I think this implies the problem lies within the ESP system and this looks quite complicated with many more sensors in operation than ABS. It has been stated elsewhere that ESP problems will turn off ABS as they are related. When I had an ABS sensor fault, this turned off the ESP but didn't give a brake failure message.

1) Other posts point a finger at the swirl valve and vacuum fault that can cause ESP problems. Where do I find these to check them out?

2) My SX version didn't come with ESP so it seems to have been an optional extra. Can this be turned off temporarily using a Lexia  to confirm the problem lies within the ESP system as I reckon turning it off using the ESP on/off button won't isolate the ESP system?

[paul.h]

The swirl valve actuator is low down at the gearbox end of the cylinder head but has a rod with a the plastic cup on the the end connected to a ball on the swirl flap mechanism but it breaks up. A new part (called diaphragm) includes the actuator for about £20 but it is possible to just swap the plastic cup from it. This only applies to the 2.2 hdi 136 bhp engine since this is not used on other engines. See problem 11. in the Common Problems pinned topic for info on replacing the diaphragm.

 

In the end you may need to have a diagnostic check using a Lexia.

[henshaw]

I think my brake failure problem might be related to the ESP system, which having read up on it seems very complicated with many sensors). If this system encounters problems, it turns off the ABS system and on my car the first message after braking fault is always ESP failure. (When I had an ABS sensor problem, the ESP was turned off but I didn't get a braking failure message) The ESP system is an optional extra (it was not fitted to my Mk1 SX 2.2HDi) so can this be turned off temporarily using a Lexia so the whereabouts of the source of the problem can be determined? (I still need to buy the Lexia)