Really strange and dangerous problem

I've obviously seen and worked on 100's of Freelanders but have never come across this horrible problem before:-

Whilst driving on normal dry roads the brakes suddenly and with no warning slam themselves on and perform an emergency stop!! This happens without you even touching the brakes!! The car stops in a straight line so it not just one brake coming on, its definitely all 4 wheels. We disconnected the ABS fuses and it seems to have stopped it happening. The only conclusion we can come up with is a faulty ABS ECU or its getting a false signal from somewhere. The plan is to change the ABS ECU, but just wondering if anyone has ever seen this before and/or cured it.

Never heard of it, but has the fluid been changed regular?

Could be the ABS/TC pump being triggered by an HDC function call in the software/wiring

Mark2 said:

Never heard of it, but has the fluid been changed regular?

Could be the ABS/TC pump being triggered by an HDC function call in the software/wiring

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No idea on the history of the car, was a cheap buy due to transmission only consisting of jelly. Will be having fluid change along with ecu and maybe pump (depending on what parts we get from the breaker). My concern is its a faulty trigger caused by wiring rather than ABS ECU, hence why i asked if anyone has seen it before.

Possible, but don't rule out transmission lock up in those circumstances

Mark2 said:

Possible, but don't rule out transmission lock up in those circumstances

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its not the transmission locking up, its 100% the brakes being applied

Good luck,

Would be interested to hear how this works out

My appologies Austin,

I just read another thread and realised who you are
(wouldn't have guessed from the opening post, and wondered what you meant then)
Makes my transmission statement look naive

Mark2 said:

My appologies Austin,

I just read another thread and realised who you are
(wouldn't have guessed from the opening post, and wondered what you meant then)
Makes my transmission statement look naive

Click to expand...

no worries, i don't post blatant self promotion . Infact this post has the potential to make us look clueless But its such a strange one and something i've not come across on any car ever!!

I have a Disco 2 TD5 and today it did something like this. It was make a whinning noise and then suddenly it juddered to a holt as if brakes where on while driving. It came a stalled stop and the ABS light was on. Got a tow home with engine running and out of gear, whinning noise still there and doesn't change if clutch is in or out but didn't judder to holt. Frightened to drive it now

Mikegrebo said:

I have a Disco 2 TD5 and today it did something like this. It was make a whinning noise and then suddenly it juddered to a holt as if brakes where on while driving. It came a stalled stop and the ABS light was on. Got a tow home with engine running and out of gear, whinning noise still there and doesn't change if clutch is in or out but didn't judder to holt. Frightened to drive it now

Click to expand...

ive had odd sensor issues cause brakes to come on with d2s,not commonly but a few times

I've seen a similar thing on a non LR vehicle. I believe that in very rare circumstances the ABS ECU can activate EBD (electronic brakeforce distribution) without warning, maybe triggered by a sensor fault? This effectively bangs the brakes on as hard as is possible, like the ECU doing an emergency stop.

Does it do it in any gear?

I guess it could be either the HDC or TCS but if its doing it in any gear it may well be the TCS. The only thing that would cause it in normal programming would be if it suddenly lost signal from both back wheel sensors. Would assume the front wheels were spinning and pull a "lol nope"

This will translate to 4 wheel braking through the VCU so would come to a violent stop. I'd be checking the rear sensors to the plug on the ecu, but also the power feed to the ecu as well - a 1 second power drop out can cause all sorts of insanity. Friend of mine used to have a 205 with a loose power terminal on the ecu and it'd occasionally freak out... intermittent is such a nightmare to diagnose!

Edit: this a manual or an auto given your jelly comment?

My sons Imprezza WRX had a faulty ECU which caused it to send a jolt through the car. Thankfully it didn't cause the brakes to lock up but the reason I mention it was he was able to replicate the fault as it seemed to be temperature related. On a very cold day it might not happen at all but over the summer it happened every day at around the same distance from home. He took the car to a Subaru specialist who said it was only the fourth time he'd seen an ECU fault like it in 30 years.
Has your customer been able to spot any pattern to when it happens?