Brake imbalance, ABS light on.

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Brake imbalance, ABS light on.
#1
Recently got my MOT (a pass, yay!) but with a few advisories and have had a few things of note since then.

Can't seem to attach images, so I'll include a link to the MOT results

Page 1: https://drive.google.com/file/d/1OOKwPem...share_link
Page 2: https://drive.google.com/file/d/1OBr_wbm...sp=sharing

Now, the exhaust blew on the way back and after *weeks* of faffing to get the right parts, I've finally replaced the catalyst. But now I have some symptoms with braking.

When I start the car, ABS light is not on, however when I press the brake even gently the ABS kicks in. After a minute or so driving, the ABS light turns on and remains on. After about 10 minues driving tonight, the handbrake light lit up for about a minute then went off (I understand this might be low brake fluid?).

Got some new brake pads for the rear on the way, but I feel like theres likley to be more issues given the mention of brake imbalance on the MOT sheets and the fact the ABS light is always on. So figured I'd come and ask if anyone has any pointers on where to look first.

Thanks very much Smile

Tony
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#2
I would change the brake fluid and give the brakes a good bleed. If this doesn't solve the issues than your ABS module might be bad...easily changeable with a used one...the biggest issue might be unscrewing the brake lines than go into it. They will likely be corroded or seized.
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#3
Hope it isn't too late to offer some advice. Appears the main problem with brake imbalance was handbrake so going to suggest you need to fit new handbrake cables. New pads may sort slight rear hydraulic brake imbalance, as long as the caliper pistons seem to move freely. A bleed can't do any harm.

As for the ABS light, I'd check associated wiring & other components before condemning the ABS module. Full diagnostics (incl of the wheel speed sensors) are quite involved but easy to check no corrosion on any pins for the ABS module multi plug. Also check the brake pedal position switch as this is part of the ABS circuit & could have an intermittent fault. A lot can be tested from the ABS module multiplug. I have pinout details for testing a '97 2.0 16v petrol but have no idea if that would be the same for a 2001 HDi.  (I got the info from Autodata but am no longer subscribed to it).

Brake light flashing on could also be faulty handbrake switch.
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#4
Thanks very much for the suggestions - I should have mentioned in the past 12 months shes had new rear calipers, fluid changed (or at least flushed through well) and various other new brake related parts.

Including handbrake cables, I forgot I'll absolutley have to tighten those! They'll be settling in now and need readjusting. Thanks very much Mighty306 for that.

Just wondering, I had the front end jacked up to work on the exhaust, theres nothing around that area I'm likley to have knocked or affected is there? Only thinking about it, the ABS light only came on after doing that job, so perhaps more than coinsidence.

The rear right light cluster also flooded a few months back, ended up drilling a hole in the base as I could not get it to seal well enough to keep water out.

So I'll adjust the handbrake cables first to get that out of the way. After that I'll have a look at the wireing for the ABS as you said, I know I read one thead with similar symptoms where it just needed a good clean.

Thanks very much, I'#ll report back afterwards Smile
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#5
I can't think of anything near the exhaust at the front of the car that you might have disturbed & affected the ABS. I think the rear wheel speed sensor wiring runs adjacent to the brake lines on the passenger side, just behind the cill. The N/S front comes up through the wheel arch & only has a short way to go to the ABS module. Cant remember the route taken by the front O/S wheel speed sensor wiring. Worth tracing it all back & doing a visual inspection to check the wiring didn't take a knock & become damaged.

Could all be coincidence as you say. I have a very vague memory of the brake light switch causing an issue for someone else. It's really inaccessible unfortunately (above the brake pedal close to where the steering column goes through the bulkhead).  As I said, it's possible to test at the ABS multiplug but you'd need the pinout data. If you're looking to keep the car longer term it's probably worth signing up to a trial with Autodata & downloading all of the wiring diagrams & associated diagnostic info. You have to be careful to cancel it before the trial ends though, otherwise you'll get pulled in to an expensive ongoing subscription.  (Some of the suggested diagnostic tests aren't that great as they recommend just testing voltages at the plug & that doesn't tell you how the circuit behaves under load. A corroded or damaged wire hanging on by one strand can still show 12v with no load but would be unable to deliver the current normally required of the circuit).

Hope you get to the bottom of it relatively easily. Cheers for now.
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#6
It's worth checking all connections on the ABS and sensors as they can corrode / fill with water just like every other Peugeot connection and just one will turn the light on.
Mine is intermittent - or on half the time, the clears, then comes back - since I went in for lunch and left the bonnet open. Cue: sudden downpour, and I might as well have sprayed around the engine compartment with a hose. Everything went haywire - firing on 2, firing on 3, all four then coughing and cutting out ? Touch wood everything else has cleared up except the ABS light - which will fail the TüV on Friday if it pops on at the wrong moment... ?

Which brings me to a question... can you feel or hear the ABS motor when it's running?
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#7
I realise this is over a year old and nobody uses forums much these days, but just wanted to reply (since I apparently never did) with the (partial soloution).

Turns out the front right ABS Reluctor Ring had split and was in the process of falling off. So thats why, upon the vehicle moving, the ABS sensor couldn't sense the (nonexistant) ring and thus the light would come on.

Handbrake light is most likley the switch by the handbrake itself, though havn't confirmed 100% yet.

Brake imbalance never quite got sorted, but I'm about to change the rear beam so going to give the rear brakes a good going over (again)
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#8
As Johnny said previously, if you need to / choose to remove callipers when replacing your rear beam, be prepared to replace some of the hard brake lines as well.  The nuts & the lines fuse themselves together so when you undo the nut it twists & damages the line (to a compromising degree).  I've had to teach myself to make up new lines from cupro-nickel pipe - not too difficult & can direct you to decent tools & resources if you need.

If on closer inspection you decide the rear callipers are shot they still seem to be readily available & only about £40 each.
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