12-06-2012, 10:37 AM
My SRS system has been completely on the fritz for the past 6 weeks or so, but I've been too preoccupied with seeping headgaskets and oil geisers to deal with it.
I have swapped the steering wheel and airbag, and swapped out the seats, seat belt switches, and passenger occupancy sensor, and none of those things caused any issue with the SRS light at the time of installation. Except one day on my way to work the light popped on for no reason whatsoever.
I had my shop pull the codes, and it said both seat belt switches were bad. I found a fix online to wire a resistor in place of the switch and trick the sensor into thinking they are always buckled, so I bought a $40 SRS reader and attempted that. It worked, for about 5 minutes, then the light would come back on. Go to pull the code again, and there's no code. I can clear it but it comes back after 5 minutes of driving.
I broke out the multimeter and started testing. With the car off, the seat belt circuits have ~93ohms of resistance, they are supposed to have 100 when closed. If I turn the car on, the resistance values go CRAZY. Shorting out to 0, spiking to 250ohms, and everything inbetween. The ground on the module is fine, so I couldn't think of anything other than a toasted module. Its under the seat sort of over the diff, so I wonder if it just got toasted over time.
I bought a "tested good" module from another 1995 for $50, and forked over $150 at the shop to have it recoded to the car.
There's still a light.
The shop said it was the Driver's Airbag Firing Circuit reading too much resistance. Tonight, tomorrow, probably this weekend, I'm going to rewire the seat belt switches properly, even though they shouldn't be related, then clear the codes again. If that doesn't do it, hopefully I can pick apart the wiring behind the wheel and find the issue, or maybe one of the crash sensors has failed in the front or something.
Gotta love old cars.
I have swapped the steering wheel and airbag, and swapped out the seats, seat belt switches, and passenger occupancy sensor, and none of those things caused any issue with the SRS light at the time of installation. Except one day on my way to work the light popped on for no reason whatsoever.
I had my shop pull the codes, and it said both seat belt switches were bad. I found a fix online to wire a resistor in place of the switch and trick the sensor into thinking they are always buckled, so I bought a $40 SRS reader and attempted that. It worked, for about 5 minutes, then the light would come back on. Go to pull the code again, and there's no code. I can clear it but it comes back after 5 minutes of driving.
I broke out the multimeter and started testing. With the car off, the seat belt circuits have ~93ohms of resistance, they are supposed to have 100 when closed. If I turn the car on, the resistance values go CRAZY. Shorting out to 0, spiking to 250ohms, and everything inbetween. The ground on the module is fine, so I couldn't think of anything other than a toasted module. Its under the seat sort of over the diff, so I wonder if it just got toasted over time.
I bought a "tested good" module from another 1995 for $50, and forked over $150 at the shop to have it recoded to the car.
There's still a light.
The shop said it was the Driver's Airbag Firing Circuit reading too much resistance. Tonight, tomorrow, probably this weekend, I'm going to rewire the seat belt switches properly, even though they shouldn't be related, then clear the codes again. If that doesn't do it, hopefully I can pick apart the wiring behind the wheel and find the issue, or maybe one of the crash sensors has failed in the front or something.
Gotta love old cars.
Now: 07 Porsche Cayman S | 18 VW Tiguan
Then: 18 VW GTI Autobahn | 95 BMW M3 | 15 VW GTI SE | 12 Kia Optima SX | 2009 VW GTI | 00 BMW 540i Sport | 90 Mazda Miata | 94 Yamaha FZR600R | 1993 Suzuki GS500E | 2003 BMW 325i | 95 Saab 900S