Seatbelt and airbag warning light NOT illuminating

[C5Steve]

Bit of an odd one and unfortunately the opposite of the issues most have so no luck searching for an answer!

Both my seatbelt warning light and airbag light DON'T illuminate on start up, the belt light also doesn't illuminate when I unbuckle the drivers belt. The warning chime still works for the seat belt though.

Any suggestions on where I should be looking? I did have the centre console apart so think I might have pulled something out there perhaps....

 

[Oneball]

I reckon you’ve got a loose wire or bulbs. I did it once on a Maserati after having the dash out, forgot to connect the wire to the light, actually showed as a fault on a code reader too.

I think the ecu fit the airbag is under the heater controls. Airbag stuff usually has yellow plugs.

 

[Oneball]

PS I’d disconnect the battery for 30mins before playing with the airbag system.

 

[C5Steve]

I reckon you’ve got a loose wire or bulbs. I did it once on a Maserati after having the dash out, forgot to connect the wire to the light, actually showed as a fault on a code reader too.

I think the ecu fit the airbag is under the heater controls. Airbag stuff usually has yellow plugs.

Cheers for that, didn't have that part out though just the armrest section...will have a look tomorrow.

 

[C5Steve]

PS I’d disconnect the battery for 30mins before playing with the airbag system.

Yeah don't worry won't be going near with the battery hooked up just seems strange the seat belt light has stopped coming on as well, thinking there's a sensor somewhere I've unplugged but would have thought if an error it would have just stayed on not off?

 

[Oneball]

Yeah don't worry won't be going near with the battery hooked up just seems strange the seat belt light has stopped coming on as well, thinking there's a sensor somewhere I've unplugged but would have thought if an error it would have just stayed on not off?

Speculation here: If the C5 has seatbelt tensioners they’ll probably be controlled by the airbag ecu. The dash light is also controlled by the ecu so if you’ve maybe disconnected the ecu itself or the cable from the ecu to the light then theres nothing to switch it on.

 

[Oneball]

Cheers for that, didn't have that part out though just the armrest section...will have a look tomorrow.

Can you turn the passenger airbag off on yours? If so does the off light come on?

 

[C5Steve]

Speculation here: If the C5 has seatbelt tensioners they’ll probably be controlled by the airbag ecu. The dash light is also controlled by the ecu so if you’ve maybe disconnected the ecu itself or the cable from the ecu to the light then theres nothing to switch it on.

Yeah wasn't near the ECU so shouldn't be that. The fact th car knows the seat belt is unbuckled with the chime suggested whatever sensor is there is working though which is odd.

 

[C5Steve]

Can you turn the passenger airbag off on yours? If so does the off light come on?

No mines not got th button for the passenger airbag so can't check that

 

[Oneball]

Can’t see it being a sensor it doesn’t fit the symptoms.

 

[teamzr1]

If the problem began after you worked on the center console area it may have under stress partly disconnected a wiring harness for SIR (safety controller) and as been mentioned, normally have yellow connectors like :

(Always check fuses first)



Refer to these. Found in book 3 of the C5 service manual, section 9

SIR is mounted below the HVAC head

Follow the left seatbelt wiring below

Also, possible a ground issue, check ground splice pack S301 shown below

 

[C5Steve]

If the problem began after you worked on the center console area it may have under stress partly disconnected a wiring harness for SIR (safety controller) and as been mentioned, normally have yellow connectors like :

(Always check fuses first)

View attachment 14577

Refer to these. Found in book 3 of the C5 service manual, section 9

SIR is mounted below the HVAC head

Follow the left seatbelt wiring below

Also, possible a ground issue, check ground splice pack S301 shown below
View attachment 14578View attachment 14579

Thanks for this, I'll have a look tomorrow. Have checked all fuses in th passenger footwell and all good so hoping it's something come loose.

 

[teamzr1]

Thanks for this, I'll have a look tomorrow. Have checked all fuses in th passenger footwell and all good so hoping it's something come loose.

If access to a OBD-II diag scanner that will connect to SIR see if it shows when latching and unlatching if the controller shows
that being done
I would check the 2 wire harness from the driver side seatbelt latch that runs along the center console that then plugs into the SIR

 

[C5Steve]

Ok so quick update, after thinking about it I couldn't honestly remember if these lights ever did come on! Found some old videos of my cluster and can confirm the seatbelt light has never come on so that's obviously an issue from before I owned the car. The airbag light also appears to have never come on at start up, I've looked at what I can find online and it doesn't appear the one in the tach does light up at start up? Anyone without the passenger airbag switch able to confirm this?

 

[C5Steve]

If access to a OBD-II diag scanner that will connect to SIR see if it shows when latching and unlatching if the controller shows
that being done
I would check the 2 wire harness from the driver side seatbelt latch that runs along the center console that then plugs into the SIR

View attachment 14580

Thank you, I'll have a look at the wiring there and chase it back to the connection in the centre of the dash. There's a lot of extra wiring around there with a line lock and ICE stuff so something could have been disturbed a while ago and not put back.

 

[Oneball]

98 here. Airbag light flashes at start up.

 

[C5Steve]

98 here. Airbag light flashes at start up.

Ah thanks for that! Yeah I'm pretty sure there's a LOT more that lights up on start up than mine. My traction control and abs don't light up........ however I know they both do when in use...,.hmmmmmm

 

[teamzr1]

Might be worth a test to see how well the bulbs in IPC, dash function by turning the small knob on left of driver to change the light level dimmer
Maybe you just have bad bulbs or bad ground
If you go via the DIC to diag mode and see if and what DTCs (error codes are tripped)
If no DTCs could simply mean the bulbs are bad or something wrong with the IPC which is the dash controller

If using a OBD-II scanner and look at the parameters for IPC and see how many functions react and what the IPC reports

 

[C5Steve]

Might be worth a test to see how well the bulbs in IPC, dash function by turning the small knob on left of driver to change the light level dimmer
Maybe you just have bad bulbs or bad ground
If you go via the DIC to diag mode and see if and what DTCs (error codes are tripped)
If no DTCs could simply mean the bulbs are bad or something wrong with the IPC which is the dash controller

If using a OBD-II scanner and look at the parameters for IPC and see how many functions react and what the IPC reports

View attachment 14588

Cheers, no DIC codes so I think it's likely something that needs a dig into the above. On the plus side the handbrake light issue was just crap in the switch stopping it make contact. Cleaned it out and all back to normal so just the airbag and seat belt warnings to track down now.