Airbag light not coming on - 04 Octavia

kkelly77

Have a 04 Octavia MK I that failed the NCT for the airbag light coming on when key turned to the 'ON' position.

There are no codes for an airbag problem.

Can anyone offer some advice where to start troubleshooting?

There is a wiring loom under the driver's seat which looks to be in good condition. Thanks.

visual

If it is not coming on i would look to see if ABS bulb is blown, been removed or covered up.

A standard OBDII reader will read basic engine codes but not ABS codes. For that you'll need specific code readers or ask dealer to read codes.

kkelly77

visual wrote: »

If it is not coming on i would look to see if ABS bulb is blown, been removed or covered up.

A standard OBDII reader will read basic engine codes but not ABS codes. For that you'll need specific code readers or ask dealer to read codes.

ABS light is coming on, as well as other warning lights. Airbag appears to be the only one not lighting up.

visual

kkelly77 wrote: »

ABS light is coming on, as well as other warning lights. Airbag appears to be the only one not lighting up.

Sorry my mistake but same advice check the airbag light first it might be blown

The wires going to seat are to detect passenger occupancy if faulty I would expect the airbag light to remain on.

Basic code readers don't read airbag codes either.

The normal operation of airbag light is on when ignition turn on (engine not running) and off once engine starts running.

If the bulb is OK you could be looking at airbag module and would need the codes read by dealer or a specific reader for your car to confirm before replacing anything.

punisher5112

Do you have the car long?

Did you put through nct previously?

John T Carroll

visual wrote: »

Sorry my mistake but same advice check the airbag light first it might be blown

The wires going to seat are to detect passenger occupancy if faulty I would expect the airbag light to remain on.

Basic code readers don't read airbag codes either.

The normal operation of airbag light is on when ignition turn on (engine not running) and off once engine starts running.

If the bulb is OK you could be looking at airbag module and would need the codes read by dealer or a specific reader for your car to confirm before replacing anything.

If the ignition is turned on but the engine not started then the airbag light will stay illuminated for 4 to 5 secs and then go out.

John T Carroll

kkelly77 wrote: »

Have a 04 Octavia MK I that failed the NCT for the airbag light coming on when key turned to the 'ON' position.

There are no codes for an airbag problem.

Can anyone offer some advice where to start troubleshooting?

There is a wiring loom under the driver's seat which looks to be in good condition. Thanks.

Looked up the schematics for a VW Golf/Bora, when you turn on the ignition, it sends 12V from the ignition switch to the Airbag Control Unit which is located in the passenger footwell, this is a black wire towards one end of the Control Unit, if you can locate this you could just see if the wiring harness is pushed in properly, if handy with a multimeter you could test for 12V at this connection with the ignition on. A VCDS (or dealer) scan is probably the best/safest way to go as I wouldnt mess around too much with this system. I cant send you a scanned schematic as this system will not accept a file with a .tif extension.

kkelly77

Hello all.

Sorry for the late reply, I didn't get any notifications that there were more posts to the thread.

I took the dash cluster apart and found that the airbag LED was missing. Don't know if this was taking out purposely or somehow broke off. I assume it was the former. I've also attached a photo.

The airbag LED should be on the left in the photo but as you can see it is missing. I used a "spare" LED seen on right, which has no purpose, as there is no symbol to illuminate in that particular position.

I soldered it into position and refitted the cluster back into the car. When the key is turned to the 'On' position, the usual lights come on, including the airbag light. The airbag light goes out for a second or two but comes back on and stays on.

I'm assuming this means there is an issue with the airbag system and will need a VAG-COM tool to find out.

George Dalton

kkelly77 wrote: »

The airbag light goes out for a second or two but comes back on and stays on.

I'm assuming this means there is an issue with the airbag system and will need a VAG-COM tool to find out.

Exactly. VCDS or any other decent scan tool will tell you what the issue is.

kkelly77

punisher5112 wrote: »

Do you have the car long?

Did you put through nct previously?

It went through the NCT a little over a month ago but only failed for CO2. I was over the 28 day period for a retest, so it went in for a full test again. This time the airbag light failed. TBH, I'm not sure if it was like that for the previous test and the tester didn't spot it. I didn't even cop it

John T Carroll wrote: »

Looked up the schematics for a VW Golf/Bora, when you turn on the ignition, it sends 12V from the ignition switch to the Airbag Control Unit which is located in the passenger footwell, this is a black wire towards one end of the Control Unit, if you can locate this you could just see if the wiring harness is pushed in properly, if handy with a multimeter you could test for 12V at this connection with the ignition on. A VCDS (or dealer) scan is probably the best/safest way to go as I wouldnt mess around too much with this system. I cant send you a scanned schematic as this system will not accept a file with a .tif extension.

Can you convert to PDF online?

John T Carroll

kkelly77 wrote: »

It went through the NCT a little over a month ago but only failed for CO2. I was over the 28 day period for a retest, so it went in for a full test again. This time the airbag light failed. TBH, I'm not sure if it was like that for the previous test and the tester didn't spot it. I didn't even cop it



Can you convert to PDF online?

If you are watching; is is the last self-test LED to extinguish but I suppose the NCT testers are looking for this now and dont start the engine until confirming it.

Converted to PDF but the file grew from < 2.0MB to > 11.0MB so still cant download it, if you google "Briskoda" you should be able to get a drawing for the Octavia.
I was able to read and subsequently reset a Passat airbag fault code with a Autel Maxscan hand held scanner a few years ago for some one and cant remember if it pointed to the exact side but it just needed breaking/reconnecting the connection block. Even if the fault itself is gone now you will still need to reset it with a VCDS (or the Maxscan) or whatever, my own Maxscan which works on all VAG models up to and including 2008 is out on loan to someone at the moment but I can get my hands on a VCDS at short notice, if you are up the country someone might assist you there otherwise you will have to go to the "dealer".

visual

I would guess that the LED was removed by previous owner to hide faulty airbag issue.

The fault you have now with ABS is similar to fault I had with my BMW. My standard OBDII reader couldn't read the airbag module. I bought a BMW OBDII lead to USB and ran BMW software on laptop and it was sensor in passenger seat intermittent going faulty.

Unfortunately it's not uncommon for a previous owner to hide faults by taking bulbs out or covering up warning lights and pass on car. NCT are supposed to check these but sometimes they miss and it can be a few years into ownership before its noticed.

Cordell

I would guess that the LED was removed by previous owner to hide faulty airbag issue

Airbags faulty and LED missing - nothing to guess here, this is exactly what had happen.
It can be a problem with the wiring or airbag computer or it can be something worse, like the car was crashed and the damage hidden.

kkelly77

Update - Had the car in with the local mechanic. Issue was code needed to be cleared which was a surprise considering the LED was "missing".

John T Carroll

Thats interesting, I wonder would it flag a fault code if the LED was "blown"/removed deliberately, if there was no fault on the airbag system itself then its hard to believe that anyone would remove it.

dodzy

kkelly77 wrote: »

Update - Had the car in with the local mechanic. Issue was code needed to be cleared which was a surprise considering the LED was "missing".

So, has a new LED been fitted to the cluster and error-free? It was definitely removed to conceal a problem. Whoever took it out (I'd say it's safe to assume the last owner did this, and following on from this...) would know at least enough about cars to have the original fault diagnosed on software. Had this been a cheap fix, my guess is he would have done it to avoid the purchaser spotting the absence of the light on the IGN sequence, which you did unfortunately.

Eitherway, I hope it works out for ya

John T Carroll

A rather dirty trick if done by the previous owner as its safety related and could result in fatalities for the occupants if the bags didn't deploy, I would be quite happy if the NCT spotted this in my car, I would say that 99% of prospective buyers wouldn't look for this, another warning LED to look out for is the front brake pad wear indicator which should illuminate as well when the ignition is switched on, this has often been frig-ed as well by removing the terminal block and shorting out the contacts.

kkelly77

I agree with everyone that a previous owner purposely removed the LED. How would it ever break of the PCB in fairness? :rolleyes:

Now that we've solved that problem, can I hijack my own thread and ask for advice on the CO2 emissions fail part of the NCT?

Originally failed for both Lambda and CO2 (0.28 IIRC). Lambda was sorted by fixing a pin hole leak in the exhaust and a helpful dashing of Dipetane for the CO2 prior to retest. Passed on Lambda but failed even worse on CO2 (0.48).

Mechanic said it was the cat (connects to manifold). I sourced an original second hand one & got it fitted. The original one looks pretty clean though. Car tested again and still failed CO2 (0.42). Tried some Cataclean and an Italian tune up. Failed a fourth time for CO2 (and airbag light first spotted).

Back to mechanic, who suspected that the replacement cat may not have been in good enough condition and is possibly not working. However, did notice a very small shudder from the engine while running and suspected an ignition issue. All coil packs were tested for resistance across pins 1 + 4 and all came back with the same value 0.386 kohms. All connectors to coil packs had 12V DC. Also, spark plugs were replaced a few months ago. There are no codes when connected to scan tool.

He suggested buying a new cat but I'm sceptical this will fix the problem, as the CO2 measurements are varying quite a bit. Any thoughts? Thanks.

P.S. Can anyone identify the black part in the photo attached with the power cable going to it? There is a snapping sound coming from it intermittently.

Special Circumstances

Charcoal canister for evaporative emissions control.
Noise is probably just the solenoid tapping away - I have no idea what sounds normal or not normal for these.

Cordell

I guess you fail on CO, not CO2. That can be that the engine is running rich or indeed the cat has failed. Are you sure that the second one was good? Is the fuel consumption higher than normal? Is the HC also up? You should get your car to a garage that has an emissions tester and enough knowledge to do some advanced diagnostics.
Or you can do what I did after spending 600E+ on a full exhaust replacement just to have the CO go up a bit instead of down, go to a garage that will install a second universal cat

kkelly77

Cordell wrote: »

I guess you fail on CO, not CO2. That can be that the engine is running rich or indeed the cat has failed. Are you sure that the second one was good? Is the fuel consumption higher than normal? Is the HC also up? You should get your car to a garage that has an emissions tester and enough knowledge to do some advanced diagnostics.
Or you can do what I did after spending 600E+ on a full exhaust replacement just to have the CO go up a bit instead of down, go to a garage that will install a second universal cat

My mistake. Failed for CO.

I have no way of knowing for certain if the replacement cat was good, other than confirming it looked clean. It was from a breaker. I will need to check the report to confirm HC readings.

What happened with you car that the CO went up after replacing exhaust and cat I assume?

Cordell

No, I did not replace the original cat, too expensive relative to the car value, but I replaced everything after it, the flexi tube, the pipes and mufflers. After all that and after pouring some Dipetane and some motorway high rev driving the CO reading was a bit higher than the first one. So I went to a different garage that said that the cat is gone and either a new cat for 1 grand or an additional cat welded in for 170E.

John T Carroll

kkelly77 wrote: »

Originally failed for both Lambda and CO2 (0.28 IIRC). Lambda was sorted by fixing a pin hole leak in the exhaust and a helpful dashing of Dipetane for the CO2 prior to retest. Passed on Lambda but failed even worse on CO2 (0.48).

P.S. Can anyone identify the black part in the photo attached with the power cable going to it? There is a snapping sound coming from it intermittently.

The reason for the higher CO is that you were inducing dilution air via the holed exhaust which resulted in low CO and a high Lambda, with "no hole" there was no dilution so you got a normal Lambda but unfortunately high CO.

Re the charcoal canister solenoid: If you are hearing the solenoid operating at idling speed then it shouldnt in my opinion and just could be the cause of the high CO reading, the ECU pulses the solenoid valve only when the engine is at normal operating temperature and is under load...thats how it is supposed to work on my VW models at ant rate. The reason for only pulsing it when the engine is under load is to avoid having a overrich mixture (at idling). I dont know how it operates under extended idling conditions.

kkelly77

Cordell wrote: »

No, I did not replace the original cat, too expensive relative to the car value, but I replaced everything after it, the flexi tube, the pipes and mufflers. After all that and after pouring some Dipetane and some motorway high rev driving the CO reading was a bit higher than the first one. So I went to a different garage that said that the cat is gone and either a new cat for 1 grand or an additional cat welded in for 170E.

The Octavia has 2 cats. 1 is part of the manifold assembly and the other runs straight under the car.

I'm half tempted to replace the one under the car for a new unit as they are relatively cheap (€60) compared to the other cat.

kkelly77

Update - Got the 2nd cat, located under the car, replaced today. Passed emissions with flying colours.