Good evening all -

Tackling the last MIL on my instrument panel..... my SRS light. Spent this afternoon and evening going through the steps on Brendan's diagnostic DIY (thank you sir - if you're still around here!). Everything seemed to be in reasonable spec until got to the Safing Sensor voltage supply and return tests. No measurable voltage noted on the supply test, and unsurprisingly, no measurable voltage on the return test. I removed the kick panel and ECU and pulled the whole thing out to inspect it and the wiring. No obvious visual defects to it or the wiring. I attempted some additional continuity tests to rule out any hidden damaged wires and came up empty as well.

At this point, I'm wagering it's either an internal fault in the sensor itself (which is epoxy sealed) or something's up with the control unit internally causing it to not feed voltage. Anyone have any experience with one of these things? Are there any other wiring points I should check out that weren't listed in the airbag diagram on the DIY? A used safing sensor is cheap enough on eBay... I may consider taking that gamble but figured I'd ask here first.
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Also - I did pull the control unit out and popped the blue cover off - circuit board and thermal fuse appear fine, visually.


Thanks!

 

The thermo fuse would probably and best need to be removed and tested with a meter

Easier said then done but you can get a false meter reading if remained in circuit ( sneek sircuit )

A conductive path if seen through a sneek sircuit would falsely say things are OK

When you want the airbags to work .....................................

I ' ll read Brandens Doc tomorrow and discern your findings

" No measurable voltage noted on the supply test, and unsurprisingly, no measurable voltage on the return test "

Brendan is certainly more up to speed than I am

 

Well lookie there

 

Thanks. Yep, I've already gotten to the airbag control unit and everything. I did also check fuse 17 in the RH rear seat fuse box. It was not blown, but I did not do a continuity test of anything back there either.

I've started cross-referencing compatible Ford control units on ebay.

EDIT: I pulled the control module out of the car a second time and popped the blue cover off. After looking at pics in another thread, I did not realize the thermal fuse has a plastic cover over it. I popped that off and did a continuity test and there was no continuity on the fuse.

 

Got you a link from N Bath with a V - 12 in New Zealand with that fuse

Airbag light on after battery drain - Jaguar Forums - Jaguar Enthusiasts Forum

see post # 32

 

these are able to store dtcs in the cluster with some crude way of counting the flash/pause output. the dtcs never go away you have to manually clear them

i’m 99% sure if you use a test light on pin 4 you can get the normal flash codes these things are supposed to have.

 

Double checked the harness that goes to the safing sensor in the footwell again and no visible damage noted. Performed a continuity test as well, even manipulating the harness around by hand to see if there was any sort of intermittent issue. Nothing happening there.

Received the Ford airbag ecm from eBay Friday - looks like that’s a dud as well as there is no continuity on the thermal fuse on that one either. Plugged it in and ran the safing sensor test in the airbag DIY with same results as before.

was looking at the original ecm board out of the plastic case this morning. Found a Ford truck forum where it looks like several fellas have gone and replaced the thermal fuse by itself with successful results. Also found what appeared to be a leaking 100uf capacitor on the board. Wonder if that’s what caused the fuse to go and not the safing sensor? We’re gonna find out. Ordered some replacement caps and 167°C thermal fuses on Amazon for about $10. Figure I have a better shot at this than gambling with 25+ year old eBay ecms.

 

Good find on the Ford area

Was there a part # on the 167°C thermal fuse ?

I still have to go through mine as my bags were blown as a actual accident in it's previous life and I have replacement airbags installed , just not hooked up

 

Just wanted to update here - I replaced the leaking capacitor on the airbag ECM, along with the thermal fuse. I performed the entire diagnostic procedure from Brendan's DIY again and this time I was successful with the safing sensor voltage tests. I started the car up with the load resistors still in place and the airbag light performed its initial check on start up and then remained off, which is the first time it has done that since i've had the car! I disconnected the battery and let the car sit overnight. Re-installed/connected the driver and passenger airbag modules and have been driving the car for several days with no airbag light.

I'm calling it a win.

Per one of the Ford truck forums, the part # for a comparable thermal fuse is NTE8167 from Digikey's website. I wound up buying a generic version on Amazon which appears to be working. The biggest difference is that the "legs" on the replacement fuse are thicker than the original - I am still unclear if the fuse on the ECM board is a 10A or 15A. I wound up with using a 15A and just had to get a bit creative with the soldering. I left the "legs" from the old thermal fuse in place and was able to sort of use them to help anchor the replacement fuse to solder in. The plastic covers will not fit over the fuse/resistor assembly so I wrapped it in electrical tape similar to what the Ford truck guys did.

 

Thanks ,

I'm ordering one to be ahead as I do the final operational check when I get there

Axial Lead Thermal Cutoffs (TCO) | Semiconductors | NTE Electronics, Inc. (nteinc.com)

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