2005 NP front brakes randomly lock on their own

[Scuzz]

Please help. My 2005 3.5 L auto exceed with only 180000 km will randomly activate the left front brake on its own whilst driving. The front right brake will compensate momentarily. My foot is nowhere near the brake pedal. The car shudders for a second under front brakes. Both brakes then release. Lasts a second or two. ABS light comes on. Brake lights too. Car continues in a straight line. Can happen at slow / fast speeds and uphill/ downhill, possibly more likely on a slight turn. May not happen for days, then will happen three times in 3 km.
Seemed to begin after I had front end work done including discs machining, new oil pump etc.
Been to 4 separate mechanics, including a major Mitsubishi dealer.
3 out of 4 could not find a problem on their computer read out.
They said to bring it straight in if the problem happens again. Thats not easy if your on your way to work
The fourth ( the guy who did the brakes after which the problem began) found diagnostic fault of
" ABS Abnormal . Error codes 37 fail, 35 engine fail and 71 YAW SNS.self". He said "it could cost thousands without a guarantee".
Pajero has nt moved in 3 months except to run around block to charge battery when roads are empty.
It s about to be scapped as it s dangerous to me and other road users.
Any ideas anybody
thank you

[old Jack]

My thoughts are the ASCTC ECU thinks you have lost traction on a wheel so it is actuation the braking side of the TC system.

Firstly are all the tyre's fitted to the car exactly the same size, profile, tread pattern, tread depth and type pressure?

Next to check would be are all the teeth on the ABS wheel hub rings intact and clean?
What is the condition of the sensors and the wiring, this can also be tested to see if they are ok.

DO you have lifted suspension? If so measure the ride height from centre hub to under the wheel arch in a vertical line, record this measurement. Then jack the vehicle up by the body so the suspension is at full droop and then remeasure the distance between the centre wheel hub and the wheel arch. You should have a minimum of about 60mm difference between the 2 measurements.

If all of the above are ok then carry out a steering sensor and yaw rate sensor recalibration.

There may be more than 1 fault triggering the false TC activations.

OJ.

[Roofchop]

Has to be TC. It's the only thing that could operate the brakes autonomously.
Can you turn off the TC on this model?
If so do that each time you drive it if it stops happening then you're golden!
Bad sensor/wiring/computer...
You said mainly happens when turning, so wiring would be first to inspect, Maybe damaged when discs skimmed....


Can you just pull the fuse for TC to permanently disable it??







Good luck

Dave

[Lance]

How is it possible for the left and right brakes to operate independantly ?
What relay, solenoid, valve or other device or system could/would need to be bypassed or faulty to allow that to happen ?

Yep, I'm not a mechanic or expert at any level........

[spot01]

Has to be TC. It's the only thing that could operate the brakes autonomously.
Can you turn off the TC on this model?
If so do that each time you drive it if it stops happening then you're golden!
Bad sensor/wiring/computer...
You said mainly happens when turning, so wiring would be first to inspect, Maybe damaged when discs skimmed....


Can you just pull the fuse for TC to permanently disable it??







Good luck

Dave

Do you mean ASC, not TC?
Unsure whether these were fitted to this model?
Usually ASC can be switched off, but not TC.


To OP, do any ASC or TC warning lights come on when you turn the key to ignition before starting?


As the ABS light is coming on, this is somehow implicated - not recommended, but you can remove the ABS fuse to disable the ABS, but then remember the wheels may lock in heavy braking (like pre ABS cars), so drive accordingly.

[spot01]

How is it possible for the left and right brakes to operate independantly ?
What relay, solenoid, valve or other device or system could/would need to be bypassed or faulty to allow that to happen ?

Yep, I'm not a mechanic or expert at any level........

The ABS (and ASC/TC if fitted) can operate any individual brake that it needs to - that is what they are designed to do.

[nj swb]

I'm guessing the ASC system is out of whack some how, possibly related to the front end work. Was anything done to the steering / wheel alignment at the time?

If the Gen 3 is like the Gen 4, the clock spring assembly includes a steering angle sensor that feeds into the ASC system. If that is incorrectly aligned then it may think you're turning when you're really driving straight, and driving straight when you're really turning - so steering sensor and yaw sensor won't agree, which might trigger a yaw sensor error? Can you turn off the ASC? Does the problem go away if you do?

Do the suspension checks suggested by OJ, and the steering and yaw sensor calibrations.

First steering check, see if you get equal number of turns in both directions from straight ahead. If you can get more turns in one direction than the other that suggests something isn't truly centred when you're driving straight.

[spot01]

With these cars, the front wheels should be left "straight ahead" when disconnecting & reconnecting the battery.


I wonder if they had them at an angle when doing the work & had the battery off?.


With wheels straight ahead, try taking the battery lead off for 5 minutes, then reconnect.

[Roofchop]

ASC became a mandatory safety feature on all new cars years ago. So I'm surprised you are able to switch it off.


Traction control however isn't really a safety feature and can be switched off on most modern cars/4x4s I've driven.


Anyway I forgot about ASC, could be that playing up and grabbing a brake at random.....


Pull both fuses! TC and ASC!


Cheers
Dave

[Roofchop]

The ABS (and ASC/TC if fitted) can operate any individual brake that it needs to - that is what they are designed to do.

ABS can't apply a brake, it releases it when it detects lock up....

[spot01]

ABS can't apply a brake, it releases it when it detects lock up....

To be specific, the EBD & EBA functions of the system can increase pressure to a brake and the ABS can re-apply the brake after the locking ceases.

[spot01]

ASC became a mandatory safety feature on all new cars years ago. So I'm surprised you are able to switch it off.


Traction control however isn't really a safety feature and can be switched off on most modern cars/4x4s I've driven.


Anyway I forgot about ASC, could be that playing up and grabbing a brake at random.....


Pull both fuses! TC and ASC!


Cheers
Dave

The Pajero from NP (with ASC/TC) onwards is different to other cars.

[Roofchop]

How and why?


ABS on all cars only function when your hoof is on the brake pedal.


The stability control and traction control use the brakes and sensors to do their thing.


Probably talk to each other but separate units.


Cheers
Dave

[SONICMASD]

As far as I know, the only surefire way to disable both ASC and TC is to disconnect a wheel speed sensor, even pulling the abs relay under the hood won’t fully stop the system. The front wheel sensors plug in at the front of the wheel arch, just follow the cable up from the abs tone ring to the harness.

This will totally kill the asc and tc system, 3 dash lights will come on, and they will only turn off / restore the system after shutting off the engine, reconnecting the harness, and restarting.

[Scuzz]

Luv the community input.

Hi everyone. Thank you. A lot to digest there. I'm going through it one step at a time.
I'll keep you all posted