QP EPB/ABS/MSP/ASR/Suspension Warning lights - unlikely to be voltage issue

spkennyuk

Member
Messages
5,930
Hmm, my ZF GT I am totally sure didn't use the EPB. The hold function was due to the drag on the torque converter. You could hear the EPB working when it did.

Obvs the 4200CC didn't have an EPB, but again used clutch drag for hill hold. Seems odd to overcomplicate things for the F1....

C

4200 still takes a signal from the abs sensor. The QP and Ghibli are both using electric motors as far as im aware to apply the epb and hill hold.

Another reason for ABS inputs on later systems is for MOT testing purposes. Some cars have a test function that checks if the front wheels are still and just the back wheels are moving so the system knows its in a test situation for testing the EPB is working correctly.
 

spkennyuk

Member
Messages
5,930
Here you go Mr C. This will probably explain it better than i can.

 

adwoot

New Member
Messages
12
Thanks all again. Interesting on the relationship between the ABS and EPB, I like to learn more about such things. Worlds away from my first car, a Cavalier Mk2, where I happily fixed faults and problems (too regularly) without having to second guess cause, and could get parts off the shelf either from my local motor factors or scrapyard (when they still let you in with a toolbox on trust!). I think the paperclip test was the most complex diagnostics on that car!

Anyway, I digress :) EPB area in boot is bone dry and visually looks very shiny and clean. I'll try a voltage drop test, reliant on a multi-meter and my brain, but seems sensible to trial fit a new battery in any case as the resting voltage suggests it's not in tip top condition.

Final Q on the ABS for now - does it only report a fault when it detects a disparity between sensors with movement, or will it also pick up a fault while stationary? It does seem to clear about 50% of the time on ignition but comes back before I have a chance to move.
 

Zep

Moderator
Messages
9,110
It works in two ways. If the sensor goes open circuit (I.e. broken cable or sensor ring) it will fault right away. If the bearing itself is failing, it will only fault when the movement in the bearing prevents the ring from reading the speed (I.e. a significant disparity in speed readings).

Once a fault if the second type is detected it remains present, light on, until the ignition is cycled and then only faults again when it reads another fault. When it failed on my GS it would fault more and more often as the wear got worse.
 

Ryandoc

Member
Messages
1,839
Jumping in on this adwoot hope you don’t mind.

Just gone to my car, been sat in garage couple days. Battery voltages as follows:

First arrival car off 12.4 V
Car running 14.3 V
Car off again after 5 minutes idling 12.7 V

I can’t do a volt drop can I as I can’t get access to the output of the alternator under the manifold?

Ive stuck the trickle charger on for a night out of shear curiosity. The warnings were there when I started her up
 

Scaf

Member
Messages
6,511
All the symptoms you describe were what I had when my hub sensor failed, I tried various resets and new battery but alas it was time to open my wallet.
 

CatmanV2

Member
Messages
48,539
Here you go Mr C. This will probably explain it better than i can.


Having read this I think my point is you can use an EPB to do hill hold. I've just not seen any evidence that the Maseratis do use it, because you can do it without an EPB (cf 4200 and ZF equipped GT, as far as I could tell)

C
 

Zep

Moderator
Messages
9,110
Having read this I think my point is you can use an EPB to do hill hold. I've just not seen any evidence that the Maseratis do use it, because you can do it without an EPB (cf 4200 and ZF equipped GT, as far as I could tell)

C

Indeed. The 4200 and QPV/GT use the ABS pump for hill hold. I know this because someone who isn’t here these days floored his QPV with hill hold working and twisted his driveshafts, which was fun.
 

CatmanV2

Member
Messages
48,539
I have to say I still never felt any braking on my cars. It all felt like it was done with clutch / converter drag. <shrug> but I know very little ;)

C
 

Zep

Moderator
Messages
9,110
I have to say I still never felt any braking on my cars. It all felt like it was done with clutch / converter drag. <shrug> but I know very little ;)

C

I guess it’s a bit more obvious with an MC shift. But the slight delay between taking your foot off the pedal and the brakes releasing was noticeable on the GS too.
 

spkennyuk

Member
Messages
5,930
Indeed. The 4200 and QPV/GT use the ABS pump for hill hold. I know this because someone who isn’t here these days floored his QPV with hill hold working and twisted his driveshafts, which was fun.

I know from my own experience with the 4200 that if the abs sensor goes rogue then you loose the hill hold.

Two main hill hold systems on cars either use the existing abs pump and restrict pressure drop on the brake system or use a motor to apply the brakes.

Most systems only work on an uphill slope for hill hold so its also taking an input from a vehicle angle sensor.
 

Zep

Moderator
Messages
9,110
I know from my own experience with the 4200 that if the abs sensor goes rogue then you loose the hill hold.

Two main hill hold systems on cars either use the existing abs pump and restrict pressure drop on the brake system or use a motor to apply the brakes.

Most systems only work on an uphill slope for hill hold so its also taking an input from a vehicle angle sensor.

Yes, that happened to me too. And an annoying rev limit at 5500.
 

spkennyuk

Member
Messages
5,930
I guess it’s a bit more obvious with an MC shift. But the slight delay between taking your foot off the pedal and the brakes releasing was noticeable on the GS too.

I think the alfa 159 system is set at between 0.5 and 0.7 seconds between you taking your foot off the brake and it starting to roll backwards. However if the car detects forward movement it releases anyway.

So unless your parked on a hill and release the brake and just wait for it to roll you will hardly notice it.
 

Zep

Moderator
Messages
9,110
I think the alfa 159 system is set at between 0.5 and 0.7 seconds between you taking your foot off the brake and it starting to roll backwards. However if the car detects forward movement it releases anyway.

So unless your parked on a hill and release the brake and just wait for it to roll you will hardly notice it.

I think that was that mans issue, there wasn’t any forward movement until his driveshafts were like twizzles. His clutch was clearly excellent though.

It sort of stands to reason that there can’t be any forward or backward movement until the brakes are off.