SERV & TCS & ABS Light

[Simon_16v]

I've had a bit of an ongoing problem with the SERV & TCS & ABS lights.

If I press the brake pedal really slowly when stationary it seems to take a while for my brake lights to come on but before they do the 3 lights come on. But if I press the pedal as normal it doesn't come on?

Will occasionally come on whilst I'm in stop start traffic?

Thanks

 

[JamesBryan]

Will be the brake pedal sensor switch thing.

 

[Simon_16v]

I replaced it last year and it seemed to make no difference?

 

[182Trophy]

ABS sensor usually. My lights were on, so replaced it and all sorted now. Expensive as f**k for the T though. £120!

 

[Daveb172]

need to adjust the switch correctly, usually u press pedal, pull out switch, release pedal and switch clicks to rest position. But on my 172, I had to push the switch in a little more to make sure the brake lights come on as soon as u touch the pedal.

hope this helps, and makes sense!

 

[Simon_16v]

ABS sensor usually. My lights were on, so replaced it and all sorted now. Expensive as f**k for the T though. £120!

How will I know which sensor it is though? When the light is on I have plugged my code reader in and nothing comes up?

need to adjust the switch correctly, usually u press pedal, pull out switch, release pedal and switch clicks to rest position. But on my 172, I had to push the switch in a little more to make sure the brake lights come on as soon as u touch the pedal.

hope this helps, and makes sense!

I've already adjusted it, just seems to end back up in the same position prior to adjusting?

 

[Daveb172]

u need to over adjust the switch, lettin go of pedel pushes the adjuster in, but on my Clio this wasn't enough as the car would still slow down with no brake light. So I pushed the adjuster in further, that way the slightest touch on the pedal brings the brake lights on, before any braking force is applied.

hope I explained that well enough!

 

[Simon_16v]

u need to over adjust the switch, lettin go of pedel pushes the adjuster in, but on my Clio this wasn't enough as the car would still slow down with no brake light. So I pushed the adjuster in further, that way the slightest touch on the pedal brings the brake lights on, before any braking force is applied.

hope I explained that well enough!

So push the switch in as far as it'll go?

 

[sburrell93]

So push the switch in as far as it'll go?

Best way to adjust the switch is to remove it, pull the plunger bit all the way out on its ratchet type mechanism, refit it (may need to press the pedal down a bit for this since the plunger will be hitting the pedal now its been pulled out further), then once you've fitted the switch back in, pull the pedal back out by hand to its resting position and it'll force the plunger to click back in a few notches, setting it.

Just make sure your brake lights still go off after you've pressed and released the pedal though, otherwise its pushed the plunger in too far.

 

[Simon_16v]

Okay I'll give it another go. I've done this a couple of times with the original switch and another I bought from a motor factors (OEM with Renault logo removed)

 

[Daveb172]

push it in 1 or two clicks, just Check their off, then come on as soon as u touch the pedal

 

[MicKPM]

The brake pedal switch is actually two switches in a single assembly. One is responsible for tuning on/off the actual brake lights. The other is a throwback to the ECU which is used to reduce power output under braking and to turn off cruise control (if active/applicable). Both switches need to switch between open and closed circuit in sync otherwise the ABS ECU see's pressure rise in the brake module without seeing the "request" for actual braking from the brake pedal switch.

If the switch isn't correctly setup the circuits don't work in sync and the ABS module declares a faulty brake pedal switch/circuit.

Normally, I see this happen more when people are gently touching the brakes in slow traffic which causes the fault to be detected. Other times, when the brake switch is hugely incorrect it happens all the time.

Mick

 

[Simon_16v]

I must admit I do brake gently, and I can replicate the fault by pressing the pedal slowly when stationary. I do have an issue where the brake lights don't come on as soon as I press the pedal though and then get a bit concious of people behind me not seeing brake lights etc.

 

[MicKPM]

Bingo! Brake pedal switch is not faulty but it is incorrectly setup. There's such ha finesse to doing it and it's frustrating but thankfully we now have a completely different system on the newer vehicles so it's not an issue anymore. To be honest, it was only ever an issue on the last of the X65's with ESP.

 

[Daveb172]

so yea basically as I said, adjust the switch properly lol

 

[Simon_16v]

Thanks @MicKPM & @Daveb172 , whilst waiting for my other half to finish work this evening I had a fiddle. Pulled the switch all the way out and refitted it, made no difference. So pushed the switch all the way in but this would keep the brake lights on permanently, pulled it out one click and it's perfect.

Although now, every so often my TCS and SERV light come on, so I suspect it may need pulling out another click? But as soon as pressure if put on the pedal the lights come which has relieved me with the worry of someone not seeing my brake lights. So I really appreciate your help!

 

[Simon_16v]

I pulled the switch out another click and not had any more lights on the dash since Wednesday. Thanks guys!

 

[Tony Lampe]

The brake pedal switch is actually two switches in a single assembly. One is responsible for tuning on/off the actual brake lights. The other is a throwback to the ECU which is used to reduce power output under braking and to turn off cruise control (if active/applicable). Both switches need to switch between open and closed circuit in sync otherwise the ABS ECU see's pressure rise in the brake module without seeing the "request" for actual braking from the brake pedal switch.

If the switch isn't correctly setup the circuits don't work in sync and the ABS module declares a faulty brake pedal switch/circuit.

Normally, I see this happen more when people are gently touching the brakes in slow traffic which causes the fault to be detected. Other times, when the brake switch is hugely incorrect it happens all the time.

Mick

I put my DMM on the switch and discovered there's one normally open and one normally closed switch.

The 4 pins (=) of the (white) connector are labelled as follows:

1 3​

A = =​

B = =​

So the ID of each pin (going anticlockwise) is A1, B1, B3, A3.
One switch is between A1 and B3 and the other switch is between B1 and B3.

When the plunger is pushed in (brake pedal would be fully released) switch A1-B3 is CLOSED and switch B1-A3 is OPEN. When the plunger is fully out (brake pedal would be pressed), its opposite (switch A1-B3 is OPEN & switch B1-A3 is CLOSED.

I don't know which switch is associated with which function, i.e. brake lights or ABS, however on my switch, this is the timing:

Plunger Pedal A1-B3 B1-A3

 

[Tony Lampe]

Here is a table showing the switch conditions:

 

[Tony Lampe]

Here is the switch pinout:

 

[Tony Lampe]

Here is the drawing and instructions for adjustment and replacement from the Renault manual.

I think the problem may be the "automatic adjustment feature".