Airbag deployment - advice on next steps & SRS light please

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AndyF07

Active Member
Posts
134
Location
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Firstly hello as I am new to the forum and this is my first post. I have a p38 2002 4.0L which I just love. Generally in good nick but I have a problem with the SRS system.

Recently the prop shaft failed and broke. It caused damage to the gearbox but I was lucky and it could have been a lot worse / expensive to fix. Everything is running great again now mechanically. But the impact caused the passenger seat side airbag to go off. So I now have a perfectly working car but a permanent SRS light. I have tried to research my options short term and longer term and wold appreciate any advice.

Firstly in the short term can I put a resistor across the airbag connector under the seat to turn off the SRS light. If so does anyone know the correct resistance and would I need to replace the SRS airbag control module too?

To fix the issue properly how easy is it to install a replacement airbag. I can find virtually nothing online to help with the diy which leads me to think it isn't simple? I am pretty competent around engines but have never dealt with airbags systems.

My other thought was if I could find a replacement front seat(s) with airbags included would it be plug and play? I am hoping the impact sensors, belt tensioners are ok as there was no crash and nobody in the passenger seat.

Any advice really appreciated as I love the car and that engine so desperately want to get her through the MOT !!
 
AndyF07 said:
Firstly hello as I am new to the forum and this is my first post. I have a p38 2002 4.0L which I just love. Generally in good nick but I have a problem with the SRS system.

Recently the prop shaft failed and broke. It caused damage to the gearbox but I was lucky and it could have been a lot worse / expensive to fix. Everything is running great again now mechanically. But the impact caused the passenger seat side airbag to go off. So I now have a perfectly working car but a permanent SRS light. I have tried to research my options short term and longer term and wold appreciate any advice.

Firstly in the short term can I put a resistor across the airbag connector under the seat to turn off the SRS light. If so does anyone know the correct resistance and would I need to replace the SRS airbag control module too?

To fix the issue properly how easy is it to install a replacement airbag. I can find virtually nothing online to help with the diy which leads me to think it isn't simple? I am pretty competent around engines but have never dealt with airbags systems.

My other thought was if I could find a replacement front seat(s) with airbags included would it be plug and play? I am hoping the impact sensors, belt tensioners are ok as there was no crash and nobody in the passenger seat.

Any advice really appreciated as I love the car and that engine so desperately want to get her through the MOT !!
Click to expand...
Welcome to the loony zone.
@Datatek can probably help you with which resistors to use. Have tagged him for you
 
AndyF07 said:
Firstly hello as I am new to the forum and this is my first post. I have a p38 2002 4.0L which I just love. Generally in good nick but I have a problem with the SRS system.

Recently the prop shaft failed and broke. It caused damage to the gearbox but I was lucky and it could have been a lot worse / expensive to fix. Everything is running great again now mechanically. But the impact caused the passenger seat side airbag to go off. So I now have a perfectly working car but a permanent SRS light. I have tried to research my options short term and longer term and wold appreciate any advice.

Firstly in the short term can I put a resistor across the airbag connector under the seat to turn off the SRS light. If so does anyone know the correct resistance and would I need to replace the SRS airbag control module too?

To fix the issue properly how easy is it to install a replacement airbag. I can find virtually nothing online to help with the diy which leads me to think it isn't simple? I am pretty competent around engines but have never dealt with airbags systems.

My other thought was if I could find a replacement front seat(s) with airbags included would it be plug and play? I am hoping the impact sensors, belt tensioners are ok as there was no crash and nobody in the passenger seat.

Any advice really appreciated as I love the car and that engine so desperately want to get her through the MOT !!
Click to expand...
Don't waste your time replacing the airbag, the side airbags are pretty useless. I can give you details of th resistor this evening when I fire up my computer. The side airbags are all past their replacement date, I have disabled them on both my P38's.
 
Datatek said:
Don't waste your time replacing the airbag, the side airbags are pretty useless. I can give you details of th resistor this evening when I fire up my computer. The side airbags are all past their replacement date, I have disabled them on both my P38's.
Click to expand...

Thank you that would be great. Much appreciated!
 
Airbags on most cars (and seatbelt tensioners) are about 2.2ohms, although many Ford & VAG cars require 3.3 or 3.9 ohms. Plenty of plugin "bypass resistors" on eBay & elsewhere.
 
AndyF07 said:
Thank you that would be great. Much appreciated!
Click to expand...
@ AndyF07 I never found an off the shelf by pass resistor. The value that worked for my P38 was 1.5 Ohms.
1.5 ohm 2 watt resistors can be bought from the likes of CPC or Conrad but they will not sell you one. I'm lucky as I had suitable resistors in stock.
 
AndyF07 said:
@Datatek @DanClarke Thanks for the replies gents. Would this one be suitable (1.5 ohm, 2 watt ) in your opinion -https://www.cricklewoodelectronics.com/2W1R5.html?gclid=CjwKCAiAvK2bBhB8EiwAZUbP1HheRuCCWxLdEyvVhKwzWqmsug5MEWdHeoyBBG5FvfdFjy8zWgocZxoC6qUQAvD_BwE

Thanks
Click to expand...
Our man Keith ( @Datatek ) is the guru, if he says its a 1.5 Ohm 2Watt then that's what it is.
I have heard of people using a variable resistor/potentiometer to "dial in" a desired result, but that may be heresay.
 
DanClarke said:
Our man Keith ( @Datatek ) is the guru, if he says its a 1.5 Ohm 2Watt then that's what it is.
I have heard of people using a variable resistor/potentiometer to "dial in" a desired result, but that may be heresay.
Click to expand...

Cheers Dan. Sorry what I meant was just whether it is as simple as the ohm / wattage of the resistor or whether there are any other specifications which are relevant. As you can probably tell I don't know very much about resistors !
 
AndyF07 said:
Cheers Dan. Sorry what I meant was just whether it is as simple as the ohm / wattage of the resistor or whether there are any other specifications which are relevant. As you can probably tell I don't know very much about resistors !
Click to expand...
I will defer to Keith (datatek) but essentially you are trying to "fool" the SRS ecu that there is a valid and working airbag there ready to be fired if necessary, and it is looking for a specific resistance range and applying a current that required the dissipation of 2 Watts without it just melting. :)
 
Srs nightmare it don’t make sense it’s a mot fail but I’ve the lights aren’t on the 20 year old out of date air bags are fine ????
 
Hi Guys,

Thanks for all the great advice so far. An absolute goldmine of knowledge!

I've ordered the resistor as adivsed by @Datatek which will hopefully do the trick. As my airbag actually went off I believe it has logged a fault. With the fault present will the SRS light stay on even with the correct resistor in place, or will inserting the resistor turn the light off (but not clear the code)? I assumed I could clear the code like any other but a mechanic has told me I need a new ECU - is that correct ?

Thanks again for the help:)
 
AndyF07 said:
Hi Guys,

Thanks for all the great advice so far. An absolute goldmine of knowledge!

I've ordered the resistor as adivsed by @Datatek which will hopefully do the trick. As my airbag actually went off I believe it has logged a fault. With the fault present will the SRS light stay on even with the correct resistor in place, or will inserting the resistor turn the light off (but not clear the code)? I assumed I could clear the code like any other but a mechanic has told me I need a new ECU - is that correct ?

Thanks again for the help:)
Click to expand...
You need to replace the ECU, the airbag trigger is a one shot device that cannot be reset with diagnostics.
You could try taking the ECU apart and opening up the appropriate trigger unit to see if you can reset it.
 
Datatek said:
You need to replace the ECU, the airbag trigger is a one shot device that cannot be reset with diagnostics.
You could try taking the ECU apart and opening up the appropriate trigger unit to see if you can reset it.
Click to expand...

Thanks @Datatek. Just to check is it the SRS airbag ECU or the main ECU you mean? Cheers
 
It's the SRS ecu/module that stores permanent crash codes, they can't be cleared using standard diagnostic/test equipment, not even a dealer can do this. I don't know if you can do anything if you take it apart, there are companies out there who can allegedly repair
 
kermit_rr said:
It's the SRS ecu/module that stores permanent crash codes, they can't be cleared using standard diagnostic/test equipment, not even a dealer can do this. I don't know if you can do anything if you take it apart, there are companies out there who can allegedly repair
Click to expand...

Thank you Kermit. I will probably just get a second hand one. Can you just replace or would I need to code to the car ? Cheers
 
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