Random Airbag, Traction Control, Engine, Oil light warning lights

[JohnW]

After chasing this problem for the past couple years, believe I have finally nailed the problem. Given the invaluable information I've gleaned from the forum on various other issues, though I document the 'fix' for the record as it may assist someone else.

Problem would generally follow the following sequence. Airbag light comes on together with warning buzzer, then traction control light, sometimes engine error light, occasionally oil pressure light (and air conditioner stops working when this occurs). Problem would just occur then disappear, returning constantly at a seemingly random basis. Sometime could be near constant (buzzer going off all the time would drive me crazy)

ABS module showed 'date fault'. SRS module showed no error codes. Engine error codes were generally a low speed relay fan fault, a security code fault, and the data fault (what a unhelpful code, means there is a problem in the circuit somewhere). And as everything works off a single bus, it can be in any module, connection, or wire.

All the usual suggestion to fix this type of problem were tried .....
ABS module replaced, twice
Low speed fan relay replaced
Thermo fans replaced
SRS module replaced
Connections to BCM and ECU/PCM checked and cleaned

All to no avail. FINALLY (should have been the very first thing I did) was replace the Airbag and ABS fuses. Problem seems to be fixed. It's now gone the longest without the problem returning so I'm pretty confident this was it.

I didn't check the fuses previously on the assumption they are either working, or blown. The apparent problem is corrosion on the fuse 'blades' creating a poor/intermittent electrical connection in their holder. On the assumption this is the problem, I replaced every fuse in the drivers compartment panel with new ones to avoid possible problems with other circuits in the future.

Hope this may be helpful to someone else. In researching this problem I noticed quite a few people with a similar type of persistent problem despite the usual 'fixes'. I'll update this thread if the problem does reoccur.

 

[JohnW]

Nope, problem returned.

Subsequently did the Injectronics service bulletin to the BCM, checking the connections haven't gone loose using the specified tiny drill (exact same size as the pins in the BCM). Found a few slack ones, pulled them out of the plug, re-tensioned and refitted as per the instructions (no special tool required to pull each connector form the holder, just a tiny screwdriver from one of those cheap jeweler's sets. Went ok for a while, then problem returned.

If I've figured out any definite pattern, its disconnecting the battery (which obviously clears and resets the BCM) makes the car run perfectly fine for a few weeks. Then the problem gradually returns, getting progressively worse. Disconnect the battery, and the cycle starts again.

So my take on this is somehow it seems the BCM slowly fills up with corrupted crap, and then starts throwing error codes. What the source of the corruption is ?????

Latest attempts at a fix have been to clean (again) all the alternator and related earth connections, someone suggested voltage surges are the reason the BCM gets upset. And replaced the clock-spring. I had a replacement steering wheel to fit (old one was weather affected, and had been re-glued several times), so thought might as well chuck in a new clock spring in the process. As the replacement steering wheel came with air bag, fitted this different drivers airbag.

Running fine at the moment, but that may just be because of the battery disconnect. Will update if it continues to throw error lights. I'm hoping, but not confident.

 

[lout]

have you checked alternator voltage
usually causes gauges to malfunction as well as warning lights
you could also unplug your abs and drive like that for a few weeks (warning you will not have abs function)
also check the 3 plugs in corner under windscreen for corosion

 

[JohnW]

have you checked alternator voltage
usually causes gauges to malfunction as well as warning lights
you could also unplug your abs and drive like that for a few weeks (warning you will not have abs function)
also check the 3 plugs in corner under windscreen for corosion

Alternator voltage is 14.5 which is in spec according to the Gregories manual.

It's now on its 3rd ABS module (2 supposedly recondition ones) with the same problems, so unless Injectronics are just repacking faulty units I'm thinking the ABS module itself isn't likely to be the problem.

Just checked the "3 plugs in corner under windscreen". Looked ok, but regardless hit them with some contact cleaner. What turds of things to get at and unplug. Who designs this stuff.

Thanks,
John

 

[JohnW]

Problem still occurring, really bad yesterday....

BUT, driving last nigh just on dusk with the dash light up like a Christmas tree (Engine light, oil light, Airbag, traction control) and no air-con (it stops working whenever the oil light comes on). Because the light was fading, I turned on the headlights.

INSTANTLY, all the warning lights disappeared. I've left the lights turned on to test my theory, and so far while not yet long enough to be conclusive, the problem hasn't reoccurred which it would normally in this time.

So ...... what effect/change does turning on the lights make. I'm aware the BCM must talk to the headlight relay somehow, as turning off the ignition turns the lights off. But my main train of thought is are the lights being on sucking up some voltage spike problem coming from the alternator? The alternator tested 14.5 volts with the lights off using a $20 multi meter, but this cheap test wouldn't show up other more complex problems. Maybe time for a trip to the auto-electrician.

Thoughts on this, or any other possibilities, greatly appreciated?

Thanks,
John

 

[ltdslip]

Might sound weird, check the brake lights.

 

[lout]

headlights would pull the voltage down
14.3 is about maximum limit, 14.5 is too high

 

[JohnW]

Might sound weird, check the brake lights.

Might not be so weird. Checked the brake lights and found the center brake light in the wagon tailgate had a blown bulb. It's a large capless bulb, so I'll have to go to Repco tomorrow to get a replacement.

How could there possible be a connection? Well, discovered the Calais etc have a 'blown taillight warning light'. Could only be by the BCM monitoring the total amp draw of the tail light circuit. My Acclaim Wagon doesn't have this warning light. BUT.... it uses the same high BCM (I think because of the rear tailgate lock) so the internal functionality may still be operating. So it is possible.

 

[JohnW]

Went to Repco this morning fitted the new center stop light bulb onsite, now with the headlights off so far the car has run without a single error code being thrown.

What a joke (but still a good one) if this turns out to be the true fix which will take a couple weeks of running around to properly confirm.

Hundreds of dollars of parts, computer scans (auto-electrician plugged in his outrageously expensive Snap-On scanner yesterday to no result), I've been using computer software and sometimes just bridging the relevant connectors, hours and hours of cleaning terminals, wheel sensors, etc. etc ........ and all possibly for a $2 tail light bulb.

 

[ltdslip]

Let us all know how it goes...