Intermittent SRS warning

[PobodY]

Sorry if this is the wrong section, please feel free to move it if it is.

I suppose I'm just looking for a little reassurance that this isn't anything to be particularly concerned about, and that I haven't bought a lemon.

I took the car through a car wash today (I know I should wash it by hand, but I've got no hose and there was a huge queue for the hand car wash), and as I stopped to let it do its thing the SRS warning light came on with the message about visiting a workshop.

I sat there for a while starting to get a bit worried about it, then the message went away (there was only the one about needed to reset the tyre pressure monitor, which I was going to do with the air hose after washing the car).

As I drove home it came on again, then went off again.

Having done a search, I suspect this is going to be the passenger seat sensor. - My cheap and cheerful code reader probably can't help me with this one.

There's a local garage that has a Mercedes logo on one of their signs, but they claim to be Mini and BMW specialists. - Should I be paying them to read (and clear) the SRS codes, or will this go away with a little jiggling of the wiring?

 

[Codger49]

Could be worth checking the wires and connections under the front passenger seat first.

I recall posts mentioning chafing of the wires where they emerged from the seat base and also loose connectors in the connection block (think SRS has yellow connector).

Probably best to do your checking with the ignition off, seem to recall disconnecting SRS seat connections when live requires a Star reset of the resulting fault. (Although this doesn't match your experience of SRS warning coming on and going off whilst driving.)

If nothing obvious, then best to get Star reading, may be something else and you don't want to guess at SRS issues.

 

[PobodY]

Thanks. - I got the impression that you can't clear an SRS fault once it's logged, but the display on my dash had one message (check tyre pressure and reset monitor), then two (tyre pressure, plus SRS fault), then back to one.

I'm clinging to the hope that this is just an intermittent error caused by a loose connection. - Thinking about it, I did fish out a bottle cap my wife had dropped down the side of the seat so could have upset some wires.

It's only if I can't clear the error that I will need to find someone with Star to tell me what the real problem is, - Ultimately I bought it from a dealership (although not an MB main dealer) so if there is a problem I'll be trying to make them sort it out.

I'd just rather not have a problem that requires me making them sort it out. - I certainly don't want a problem with the SRS as the extra safety was one of the reasons we bought it.

 

[PobodY]

Almost a week later and it hasn't done it again. - I don't drive the car every day; so it's really only a couple of trips to the shops and back, but no sign of any SRS warnings again.

I'm now wondering if it was something as simple as low battery voltage.

 

[markjay]

You should have the fault codes read, really - it will show stored codes and will point you in the right direction.

 

[Marku]

Every time the Viano was started we got an SRS fault warning. Time before last had it serviced by an independent who queried all the fault codes and could only suggest it might be the seat sensor and cleared the fault codes but did nothing else, also apparently did not notice a faulty exhaust. Fault warnings continued up until we had it serviced by a dealer who did not comment but we have not had a fault since.

 

[PobodY]

I'm almost certain it's seat related. - Today we went for a drive to Lyme Park, and as we neared I started to get an intermittent seatbelt warning ping. It would stop, then we'd go over some bumpy road and it would start chiming again, then stop for a bit.
I assumed it's just a loose connection somewhere.

When we were ready to leave I thought I'd have a poke around under the seats, but I couldn't easily find any wires to jiggle or reconnect.
As soon as I turned the ignition on I saw the SRS fault warning was back, so tried turning the ignition off and on again; it went away and didn't come back the entire drive home... unlike the seatbelt chime, which came and went for a while before settling down and remaining off.

I might buy myself something like the iCarsoft i980 for Christmas and give them all the stored codes next time it's serviced.

 

[markjay]

One common cause is the front Passenger Seat Occupancy Sensor.

It is a thin 'mat' with a multitude of tiny pressure-sensitive switches, fitted inside the front passenger seat.

It's purpose is to stop the front passenger airbag from deploying in the event of a crash if the front seat is not occupied (thus avoiding necessary repair bill for replacing the air bag).

It can be replaced, the part costs around £100- £150, then there is the labour cost for removing/refitting and disassembling/reassembling of the front seat.

There are also Chinese-made devices that can had off eBay for a tenner or so, and that will 'trick' your SRS ECU into thinking that the front seat is occupied at all times, but this is NOT a good idea (in my opinion, anyway).

But of course it could simply be an issue with the electrical connector at the base of the seat - might be worth disconnecting and cleaning the connector - but make sure the ignition if OFF until the connector is reconnected or you will end up with a permanent SRS fault light....

Said that... this is all theoretical until such time that you actually connect the CAR to STAR and find out what exactly the SRS ECU is complaining about.

 

[PobodY]

I thought it might be worth posting the resolution to this one, just in case it's helpful to someone else.

The problem was not the passenger occupancy sensor, it was the passenger seat-belt sensor (according to my i980). - I gave the connectors under the seat a bit of a wiggle and cleared the codes.

No more SRS errors in the last month; with or without a passenger.