Technical Strange behaviour when brake pushed hard

[500sportitalia]

Mornin all,
I’ll get Straight into the problem.
Been a very well behaved car for a long time, no major problems, and looked after quite well, my wife’s had the Sport for some 12 years and doesn’t want to sell it either.
So, the other day, “fuel cut off not available” and the hill hold and esp messages, strange, power cycle, all off for a while, touched the brake, back on?
Ok, check the obvious, boot loom, I repaired in the past, couple more cracks but nowt major, make good, same fault.
Earth strap to gearbox, crusty, made anew one, not that, now I’ve noticed engine running, not moving, push brake pedal have all lights etc, push hard, ie to the floor, rev counter drops off, speedo goes to the bottom, have the red steering light on, ABS, asr the lot, foot off the brake, rev counter/speedo pop back up, steering light goes off?
Checked battery health, 87%SOH 99%SOC,
Engine running, headlights on, rear heater on, blower on full speed battery getting 13.8v (loaded) 14.1v no load,
Oh, new brake switch too so that’s out.
It’s got me puzzled I’ve got to say,
Some wise words from the collective would be greatly appreciated now.

 

[steveras57]

I was thinking brake switch as well! might be worth disconnecting the new one(how old?) and seeing if that changes the effects! puzzling just wondering if it might be a faulty new switch?.

 

[A3jeroen]

You calibrated the new switch when installing it?

gr J

 

[Jo500]

just a copy from another thread here around describing the same symptoms

Check the wiring loom where it enters the rear hatch; this is a common failure point...

Airbag lights, fuel cut off, flashing odometer | FIAT 500 (2007+)

Afternoon, I have read previous threads on this, on this forum, but cannot seem to find the thread now I’ve joined the forum. I just wanted some direction as to where I should be putting my money first with this, 1.2 Pop 500 64 plate, 33k. Had trouble starting a couple of weeks back, seemed...

www.fiatforum.com

I also have this problems since a few weeks

regards Jo

 

[500sportitalia]

Solved!!! I THINK………

Right, so, to help anyone that might (and most likely will), in future, get similar symptoms.
4 weeks on and Luigi was getting bad!, drive ok for 5~10mins, then the trouble started.
FUEL CUT OFF UNAVAILABLE, HILL HOLD UNAVAILABLE, ASR UNAVAILABLE, EPS (power steering) UNAVAILABLE, CHECK ENGINE,
AND THE CROWNING TURD…….
IMMOBILISED, NON START, CRANKS BUT WONT START AND THE LITTLE PADLOCK BOTTOM RIGHT OF THE DASH

Basically, I’ve been scratching my head for several weeks now, initially started off as the fuel cut off unavailable and hill hold…….
Been through everything, earth strap, boot loom, brake pedal switch, (NB it doesn’t need calibration, it’s a basic OC/NC switch),
Checking continuity on the CAN line between engine (ECM), ABS, EPS, OBD connector, YAW sensor and the BCM, all good, perfectly clean, main faults on MES were no cons to ECM, ABS, EPS, YAW, and strangely FIS? angle sensor (NOT! YAW sensor under handbrake)).
Swapped out the YAW from my 500c, calibrated the sensor etc etc, er-indoors took it out in the afternoon, and the damn thing immobilised itself!!!!
But, strangely enough I found you could stick it in 1st, release the clutch and crank it over, lo and behold, it started, VERY VERY STRANGE.
put the original YAW sensor back, re-calibrated, yadda yadda yadda, I took it for a drive, oh my god, 5 mins in, dash like a Christmas tree, no steering assistance, pulled into a layby, turned it off, padlock, non start, ARRRRGGGGGHHHH!!!!!!
Literally roll it back a couple of feet to try the bump it in gear trick, padlock off, fired straight away.

At this point I’m not rambling, I’m hoping other owners can say, yes, this is exactly what’s happening!

Eventually got back to my workshop, very sluggish, no power steering, rev counter on and off like mad, Speedo up and down like a brides nighty, no temp gauge, and stuff on and off like you wouldn’t believe.
And as for the fault list, endless..

going through the data line drawings again this morning I noticed (didn’t see it before), the Blue and Me does have a high speed data connection via BCM, guess it should be EOL too, so first thing this morning, get in to the telematics convergence module (passenger side, behind the speaker trim panel and low down) and disconnected it, ran PROXI ALIGNMENT, all seems ok, took for a very long run, a good hour or so, in sport mode and putput mode, rough road, small estates to work the steering at max and brakes etc,

PERFECT, NEVER MISSED A BEAT!!!!

YET,,,,,

WE’LL SEE SHALL WE


HOPE THIS HELPS EVEN JUST ONE OWNER,

LET ME KNOW