Hi there, 

last Tuesday my fiesta failed the mot with the airbag warning light not going off, I’ve tried the 2.2 ohm resistor across the disconnected airbag and tensioner leads to the control module with no effect. At one time the fault was intermittent. 
is there a connector with a resistor in where the passenger airbag would be if one was fitted?

Also someone mentioned a weight sensor under the drivers seat which I can’t find.

And finally does  the control module need resetting

I forgot, 3 different diagnostic units have been tried to check fault codes but can’t communicate with the electronics.

thanks for reading this and any suggestions you can offer.

regards 

A. Hambidge

Is the light on constantly or flashing? If flashing that will help narrow down the fault to airbag, seatbelt pretensioners, sensors etc.

Hello Amanda, there are a number of things that can cause the airbag warning light to illuminate, and most of them are not the airbag !!

Normally I recommend the use of a laptop computer and the software FORScan (it is free). It is almost as good as the real Ford dealership programme and seems to get nearly every DTC fault. I'm just not 100% sure it will work fully with a 1998 Ford vehicle, it most probably will and certainly worth trying.

You need to get FORScan from here: https://forscan.org/download.html

You will also need a GOOD connector ELM327 lead, for example: https://tunnelrat-electronics.fwscart.com/USB_Modified_with_switch_ELM327/p4541936_17045457.aspx

This should then help you find the fault, which on cars of your age could well be the 'Crash Sensor' which is located at the front near the bonnet latch.

Hi MarksST,

Its  constantly on.

Unofix, thanks for that info, will look into the testing option.

Amanda

Hi Unofix,

i don’t think there’s a crash sensor near my bonnet latch, but I will check, I’ve ordered the test adaptor for my laptop and downloaded the software ready for when it comes.

Amanda

It's been so long since I've had anything to do with that version of the Fiesta.

The crash sensor may be in a module mounted under the centre consul next to the handbrake. I will see if I can find the information on it.

The site is slow ........ but it has your Airbag and sensor details

https://ford.7zap.com/en/car/81/code.wu,1.28356,2.44091,4.15198,6.7815,7.29708,10.19958/0/2018/17264/

The Fiesta MK4 is pre OBD2 (EOBD for the European market). Ford introduced OBD2 on the Fiesta MK5 in 2000.

The Fiesta MK4 has a Ford specific implementation of the OB1 PWM protocol. For diagnostics you need Ford specific OBD1 compatible software and hardware (ForScan does not support OBD1).

Since OBD1 only includes engine diagnostics it would not be helpful in this particular case anyway.

On 12/26/2021 at 2:51 PM, A Hambidge said:

Hi MarksST,

Its  constantly on.

 

A constant light on indicates a control module failure, see here for diagnostic check.
The module is behind the access panel in the glovebox. See here

Hi Dan, 

thanks for that, the light was intermittent at one point, sometimes it would go off, almost like a bad earth or supply.

i have a friend with a scrap fiesta mk4 he’s going to let me have the airbag control module off it.

regards

amanda

 

Hi again, 

well I thought I’d found it, ran through the tests from the online manual,  Part a5 of the tests measure a resistance between 2 points mine was below the 10k ohm they specify around about 7k, they suggest replacing the wiring harness.

anyway I decided to come in and look at a wiring diagram to see where the wires off these points go.

reconnected the battery to move the car back to its normal parking place and the light came on and went out, dived into the house to get my house keys to take it to the test station and when I got back in the car the light was back on, lower brightness and with a slight flicker.

so it’s back to the drawing board

 

A bit more to add the colours on the wiring diagram that correspond to the test which measured 7 k instead of 10 according to the wiring diagram go to the passenger airbag which my car doesn’t have, would there still be a lead in the wiring harness going to a connector for this?

It  was common on cars of that era to use the same wiring harness even if the passenger airbag was not fitted. I don't know for sure about your model but again on some there was a dummy end of line resistor plug fitted when there was no airbag.

 

On 12/29/2021 at 12:27 PM, A Hambidge said:

A bit more to add the colours on the wiring diagram that correspond to the test which measured 7 k instead of 10 according to the wiring diagram go to the passenger airbag which my car doesn’t have, would there still be a lead in the wiring harness going to a connector for this?

Don't trust Haynes!

airbag wiring.pdf connector.pdf

Hi Dan62,

I decided to remove the panel covering where the airbag would be fitted on the passenger side if there was one and there is no wiring or connector there. Thanks for the diagrams, there’s not one in the Haynes book for cars earlier than 2000. The wiring colours in that later diagram show those two wires which go to the passenger airbag when it’s fitted also go to the passenger seat belt tensioner which, of course you would want to activate at the same time as the airbag. I’ve been using that online official manual which you sent the link to, I notice that there’s no wiring on that diagram to the tensioners.

Anyway thanks for the info, it’s much appreciated.

Regards

2 hours ago, A Hambidge said:

I notice that there’s no wiring on that diagram to the tensioners.

The tensioners are on a separate page.

SB Tensioners.pdf

Hi Dan62,

thanks for that, much appreciated.