ABS Problem

[Fizzy]

Hi,

I had a problem in the past where very occasionally the ABS light would stay on after starting the car. Next time I started it it would be fine, and then stay that way for a good while....

....unfortunately the light is now back on. However, this time its coming on while driving. Its not been when braking etc, just when cruising on the motorway etc.

I can vaquely recall somewhere a way of getting codes out of the ABS controller in the same was as the ECU, and what they mean. Anybody have any info on this?

I'll check the obvious (low tyre pressure, break fluid, connectors etc) but would like to know what the car thinks is wrong.. :idea:

Thanks.

[Garbe]

what about the sensors? could be mucky

[Fizzy]

Where do the sensors hide - on the hub somewhere I guess?

[Fizzy]

Strange - did a search yet again and this came up top of the list this time...

http://stephenmason.com/cars/mr2abscode.html

[Garbe]

Have you done the check?
Or is it not working because of the V6 swap?

[Fizzy]

Well, I bridged TC and E1 on the test connector in the engine bay...

.....and zip. Nada. Nothing. :(

Tried it with abs test connector connected as normal (i.e. just doing a basic ecu code check)..

...and again zip, nada, nothing. No flashes of the ecu/engine light at all in the dash, so looks like its not in test mode.

I'm bridging TC and E1 on the diagnostic connector - is this any different on the V6?

[Fizzy]

Did a quick check, and realised that for the engine codes TE1 and E1 are bridged - which was also pointed out on the thread I started in the 3vz area.

Looks like the issue is either the TC connection for the abs control unit is not wired in, or the unit has actually failed. Or possibly a fuse has blown somewhere. Gonna be fun trying to trace the wire, so may just check everything over and see if theres anything obvious.

[Fizzy]

Arrggghh! Looks like things are getting worse.

Driving into work this morning, abs light stayed off.... :thumbsup:

...on the way home, almost made it back. Light braking in a slow rolling queue of traffic, and I felt an odd, pretty soft judder (thought I might have run over something in the road, but was probably ABS kicking in?), thought I heard a bit off a hissing too......? ABS light then came on, and brake pedal bites a lot lower down...?

Does this sound like a sensor problem or something more drastic? What about the servo assist side if things - how is that driven? Could this be symptoms of a dodgy master cylinder?

Can't get any codes out of it when I jumper the TC and E1 pins in the diagnostic connector, with the ABS test connector bridged - which means either the TC line from the acu is not connected, or the acu is duff...

[Fizzy]

Thats great, thanks! :thumbsup:

I'll give it a go this weekend. I've only got a basic digital multimeter but it will be sufficient to check output/resistance levels.

Just found a web page giving details on how to change the sensors if need be. Looks like getting them out of the hub is quite a challange, especially if you want to keep them intact. [:(

[Fizzy]

Great! Thanks. I'll let you know how things go this weekend.

[Fizzy]

Right - tried the ACU code readout thing again today in case I missed something - still no joy there. :confused:

Confirmed that the ecu code checking thing works though - got error 42 logged. Believe thats due to the speed sensor wiring to get around the auto ecu.

Checked the sensors on the front. Both read as 1k ohms resistance.

The ones in the back are a real pain to get to. The off side one was below my alarm speaker, so had to get that unhooked to be able to get there. Managed it and did a reading....

165K ohms? Oh dear...

The near side one is below the fuse box, various piping and just be the coolant filler bottle. Just could not get my hand down there. Looks like I may have to move the fuse box if I can figure out which bolts to remove. So not checked that on yet.

So - looks like either to two fronts ones have had it, or the rear off side one. I'll hazard a guess that its the rear one - but would be able to confirm when I manage to test the near side rear.

In fact, just found out in the bgb that they should in fact be 0.9 - 1.5 k, so looks like rear one is definately caput....

Anybody know a good place to get replacement sensors? Should I replace both rears just in case - no idea if they should be replaced per axle... and any adjustment involved?

[Fizzy]

At least you now know where your problems at Ian. :) :thumbsup:
No adjustments needed, plug n play matey.
Did you try the wheel spin test on it?

Nope, did the resistance test first. Didn't want to jack the car up on my slopey drive with the handbrake off to allow me to spin the rear wheel if I could help it.. ;)

Considering that the resistance check is not showing an open circuit, but way off spec levels its pretty safe to say that a duff sensor is the culprit. I think. Erm.. lol bgb says to replace it if its above 1.5K anyway.

[Fizzy]

quick question - anybody know if the abs sensors are the same across the range, or are turbo ones different from na, or across the revisions etc?

Mine has turbo rear hubs on a uk na car....

[Marksman]

All I know is that the one I tried to take out sheared off as soon as I looked at it. Looked like it was a tube made out of tinfoil >:( Is this your daily driver? If so I might look at the possibility of swapping the whole hub...

Owen

[Fizzy]

All I know is that the one I tried to take out sheared off as soon as I looked at it. Looked like it was a tube made out of tinfoil >:( Is this your daily driver? If so I might look at the possibility of swapping the whole hub...

Owen

As it happens I bought a runabout when it was getting the V6 fitted, and I still have it.

Just got a quote for a new sensor - £103+vat! :eek2:

I can get 10% discount on that though...woohoo!!

Looks like 2nd hand hub may be a better option. Probably worth getting the wheel bearings checked/changed while I'm at it as well?

These little jobs tend to escalate into major overhauls. lol Still got a poly bush kit to fit as well.

[Fizzy]

Right - given the price of a new sensor, thought I would double check my readings.

Moved the fusebox out if the way a bit and got to check the rear near side sensor. I then realised that the rear sensors have male plugs on, while the front have female plugs - so I was actually checking loom resistance on the rear off side before. :blush:

So, checked them again -

Front Near side - 998 ohm.
Front Off side - 998 ohm.
Rear Near side - 996 ohm.
Rear off side - 1012 ohm.

...so still a fraction off compared to the others, but well within spec. Looks like back to testing again.

ABS light stayed off when I started it up afterwards, so took it for a test. Brake pedal is definately biting lower down than before and feel a lot spongier. Does brake though, and peddle doesn't go down anymore when you push it reasonably hard. Brake fluid level hasn't gone down at all either, so I don't think theres a leak or anything... just feels like brake assist is off?

A steady drive down the motorway, and after about 10 mins of cruising, the abs light comes on. :(

Got home, switched off. Switched ignition back on and ABS light stays on. Switched off and let it immobolise etc. Switched on again, I hear ABS click a couple of times, ABS light goes off.....

.....and about two seconds later I hear the ABS click again and the light comes back on. So looks like its failing all the time now.

Still can't get the test mode to work either. Thought I would try a long wire from the TC pin on the ecu to the E1 connector on the diagnostic plug (or does it simply need to be earthed?) - and found that in my BGB the abs ecu has 2 plugs, whereas the one on my car has 1. So guess the pinouts are probably different.

I think its because the manuals I have are the rev1/2 ones, and not rev 3?

Anybody have a pinout diagram of the rev3+/'95 abs ecu plug?

Also spotted a couple of wires spliced into the cable to the ecu plug which I believe lead off to the alarm box. The wires they splice into are both black with a silver stripe from what I can tell. Need the diagram to help identify what they are...

...and anybody know if the ABS ecu will complain if it comes on and the main engine ecu is not there? (i.e. abs ecu on, engine ecu immobolised)? Just wondering what this wiring may be doing, as ABS light does not go off until the immoboliser is switched off.

I just want to get the diag codes out of it so I can at least get some clues as to what is wrong.