1996 P38 4.6 SRS crash sensor test

Jazbar · Jun 5, 2020

Morning all.
Wonder if you good people can help me trace an SRS problem.
Symptom:
SRS light flashes. Airbag fault in display- this can be cancelled by stalk button.
So far:
Checked connectors in footwell. Replaced airbags. Checked rotary connector.
I'm wanting to test the continuity of the crash sensors (connectors are clean) but I cant find info on what I should be getting at the pins.
Any ideas?

Thanks all

kermit_rr · Jun 5, 2020

when you say flash, do you mean it comes on with the ignition, goes off then comes back on and stays on? or is it a regular blinking?

Jazbar · Jun 5, 2020

kermit_rr said:
when you say flash, do you mean it comes on with the ignition, goes off then comes back on and stays on? or is it a regular blinking?

The SRS indicator has 2 bulbs. One stays on, the other flashes continuously while ignition on and engine running.

Datatek · Jun 5, 2020

Jazbar said:
The SRS indicator has 2 bulbs. One stays on, the other flashes continuously while ignition on and engine running.

So both lamps are working? I thought the lamp only flashed when one bulb had failed. Has the wrong wattage bulb been fitted by any chance? Otherwise it needs diagnostics.

kermit_rr · Jun 5, 2020

mines a 2000 so the newer SRS system, but when I had a bulb out, the other remained lit solidly, it didnt flash

wammers · Jun 5, 2020

Jazbar said:
Morning all.
Wonder if you good people can help me trace an SRS problem.
Symptom:
SRS light flashes. Airbag fault in display- this can be cancelled by stalk button.
So far:
Checked connectors in footwell. Replaced airbags. Checked rotary connector.
I'm wanting to test the continuity of the crash sensors (connectors are clean) but I cant find info on what I should be getting at the pins.
Any ideas?

Thanks all

Crash sensors are make switches once they have been activated they must be replaced. There should be no continuity through a unmade one. If you have continuity replace the sensor.

Jazbar · Jun 5, 2020

wammers said:
Crash sensors are make switches once they have been activated they must be replaced. There should be no continuity through a unmade one. If you have continuity replace the sensor.

There are 3 wires on each front crash sensor so I presume I'm looking for an open circuit between any combination of the 3 terminals?

wammers · Jun 5, 2020

Jazbar said:
There are 3 wires on each front crash sensor so I presume I'm looking for an open circuit between any combination of the 3 terminals?

If you have early RAVE it gives diagrams for sensors. DO NOT be playing with sensors with battery connected. Disconnect battery and wait twenty minutes before touching anything SRS.

Datatek · Jun 5, 2020

Jazbar said:
There are 3 wires on each front crash sensor so I presume I'm looking for an open circuit between any combination of the 3 terminals?

The 3 wires are positive feed, negative and the third wire is for when the sensor is activated.
Once activated, in theory they cannot be reset.

Grrrrrr · Jun 5, 2020

I had a similar issue and it was the connection to the bulbs in the instrument binnacle. You can trace the connector from where the yellow wires connect to the binnacle through to the bulbs themselves. Just bend the tangs on the cap for the bulb and make sure it is clean where it contacts the printed circuit. Might get lucky.

Jazbar · Jun 6, 2020

Grrrrrr said:
I had a similar issue and it was the connection to the bulbs in the instrument binnacle. You can trace the connector from where the yellow wires connect to the binnacle through to the bulbs themselves. Just bend the tangs on the cap for the bulb and make sure it is clean where it contacts the printed circuit. Might get lucky.

Thanks grrrrr. Already done that.

wammers · Jun 6, 2020

You had better hope it's not a crash sensor they are ridiculous money.

kermit_rr · Jun 6, 2020

Needs diag. Flashing doesn't sound like a normal error to me, especially as it's only one of the bulbs

wammers · Jun 6, 2020

kermit_rr said:
Needs diag. Flashing doesn't sound like a normal error to me, especially as it's only one of the bulbs

The fact that the flashing lamp and error message can be cancelled with stalk button is very strange. Has wiring been tampered with to fit accessories i wonder.

kermit_rr · Jun 6, 2020

wammers said:
The fact that the flashing lamp and error message can be cancelled with stalk button is very strange. Has wiring been tampered with to fit accessories i wonder.

When my light has been solid on, I've always been able to clear the dash message until the next ignition cycle

wammers · Jun 6, 2020

kermit_rr said:
When my light has been solid on, I've always been able to clear the dash message until the next ignition cycle

Ok never come across that.

RangeRoller dt · Jun 6, 2020

Can’t turn mine off Airbag fault appears over everything, only thing that seems to override it is 35pmh max and it still shows up before the later message.

kermit_rr · Jun 6, 2020

RangeRoller dt said:
Can’t turn mine off Airbag fault appears over everything, only thing that seems to override it is 35pmh max and it still shows up before the later message.

Good to know there's consistency across similar models

Grrrrrr · Jun 6, 2020

Jazbar said:
Thanks grrrrr. Already done that.

Come to think on it, when I did mine the error required diag to get rid of it, even after I fixed it. I think someone said the later cars are different but you never know.

kermit_rr · Jun 6, 2020

Mines a 2000 model so later SRS it does a self check and clears the light on its own once the fault has gone

1996 P38 4.6 SRS crash sensor test

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