ScoobyDoo555

Hi there,

Got a strange ABS/PSM light issue. Car is a manual MY00 3.4 C4 with 102K (miles).

The problem can be almost forced at will - when driving, if I maintain a speed (for example, 35 mph) for about 2 to 3 mins, the lights will come on.
A turn off and back on, and the lights go.

I've an OBD reader on it and the only thing I could find at the time was error code 4460.
What I've done to remedy the problem:-

1. Changed the brake light switch (not calibrated though - didn't think it necessarily the problem due to the lights only coming on whilst the vehicle was in motion)
2. Checked all the rings in the hubs (whilst changing my brake discs)
3. Checked and reseated the ABS sensors.

My problem is that I live NOWHERE near a dealership (or Indy) with a Durametric.

I'll try the brake switch calibration in the meantime, but what else should I check?

Thanks in advance,

Dan

5CHN3LL

How's your battery? When my battery is undercharged, I see this issue fairly frequently (a couple of times a week). When the battery is fully charged, no issue.

If you have a maintainer/trickle charger, charge your battery overnight and see if the issue presents again.

Do you have stock tail lights, or are you running aftermarket LED lights?

ScoobyDoo555

New battery tbh.
No LEDs - all stock fittings.

Dan

5CHN3LL

Note the voltage next time you're driving and the lights come on. When you're cruising along, voltage should be a tick under 14. If you're seeing 12.5-13V, might be time to check the alternator wiring and/or voltage regulator.

I'd be a dollar (not a pound) that your voltage will be a bit low when you see the lights.

ScoobyDoo555

Thanks out of interest, is there a method to see the voltage whilst the car's running?
Don't really want to put a multimeter out the window

I seem to recall there being a method of using the ac display to show additional info (such as voltage)

DAn

ScoobyDoo555

I also realise that there's a volts meter in the binnacle But I don't think that's as accurate

ScoobyDoo555

Out of interest, why would the voltage drop occur regardless of time in the car (ie having time to heat up etc).... especially if I can get the issue to occur on command (when I drive at a constant speed?)

Genuine query - going for a quick drive now anyway

DAn

5CHN3LL

The voltmeter on the dash is sufficient for determining if you're getting the correct output from the alternator.

ScoobyDoo555

thanks

ScoobyDoo555

Just got back from a drive. Voltage stayed ROCK solid at just below 14v all the way (and the lights came on after about 500m of constant 50mph driving.

Am I looking at Durametric?



Dan

bcrdukes

I'm thinking brake light switch.

ScoobyDoo555

I'd thought this initially, so I changed it. However, I didn't know you had to calibrate it? Don't even know how to do it

ScoobyDoo555

Out of interest, reading around the net, there seems to a link to a faulty MAF.
Although there are NO performance issues. (I recall that a failing/faulty MAF can result in seeing the car hunting for revs at idle.)

Am I barking up the wrong tree here?

DAn

5CHN3LL

It CAN be the MAF - but since the MAF is an expensive part, I look for other causes first.

Since your voltage is constant, my alternator/voltage regulator theory is out the window - and since your taillights are not aftermarket/LED, that avenue is a non-starter as well.

If you know anyone else who has a 996, see if they'll let you switch MAFs for a day. Even if yours is going out, it won't hurt his car any to run with yours for a day - and if the issue remains unresolved, you won't have spent $200 to replace a perfectly good part...

ScoobyDoo555

I've also asked a "local" Indy how much for a go on their diagnostic computer.....
Will see about a MAF

Thanks

Any other suggestions?

Dan