Sorry, but I am looking at the circuit diagram for the SRS system in a 99 Civic and there is NO input from the seat belt warning light. They are not connected. It's a coincidence.


Don't you think it's kind of obvious whether or not there's someone in the driver's seat? [8D]
Newer cars have a sensor that determines if there's an adult sitting in the PASSENGER seat as part of the airbag system, but not the car in question here.

 

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Cool - then based on the information he provided in the original post, you got any better ideas where to start? I'm all ears (eyes, in this case).

That's the problem with trying to help people troubleshoot their problems on a forum - people who have problems, never quite relay ALL of the information, and those to try to help are going based on what they know about the problem based on information provided and their own experience.

My input thus far has been based on common-sense and general experience troubleshooting automotive issues. I'm not a SME on '99 Honda Civic electronics or SRS systems, but I have successfully worked on my '95 (without setting it off) by reading and following simple instructions. One things that's really disappointing is when it seems easier for people to crap on other people trying to help, than it is to offer up any actual help in the first place.

My recommendation still is: plug the thing back in and see if the light goes back out. Wired or not (according toyour diagram, which I can't see from here), if the light goes out, it's connected - SRS probably receiving a 'Go/No Go' signal from the BCU. If it doesn't, what's the harm? Worse case scenario, you've plugged the seat belt warningback in and the light stays on.

If the light goes out though... I suppose you could just call it 'F00kin' Magic' and move on, rather than concede that I might've been right. Which even though it would make me feel better, it's not really important to me anyway - like I say, I know exactly why my SRS light's on.

Ever started your car and gotten out?

I'vehad friends with a fewcars that would not even start unless the seatbelts for the occupied seats were fastened ('74 Saab 99, '88 Saab 900S, '78 Porsche 928S, '79 VW Scirocco...), but once the car was started - it continued to run even if the seats became unoccupied after it was running.

I watched the guy with the '74 Saab have fits because his car wouldn't start - because ofa 50lb bag of dog food sitting in the passenger seat. Fastened the seat belt, car fired right up. Did the car know there was a passenger? Not really... it just knew there was something heavy in the front seat.

A friend was scraping his windows while the car was running ('88 Saab 900S in SLC, Utah during winter - had to get in, fasten the belt, start the car, unfasten, and get out), a neighbor slid down the hill in his Ford Truck and slammed into the front bumper of the car - airbag deployed - my pal was smart enough to step back from the car before the truck hit it. Did the car think there was a passenger in the driver's seat - Yes: because the car was running, and all of the conditions it required to run andarm the airbags had been met prior to my friend getting out of the car.

So to answer your question: No - it is most definitely Not Obvious to the car whether the seat is occupied or not. Cars only work the way they do based on conditions being met. If the seat's occupied, but the belt's not fastened, the warning buzzercomes on for a period of time - when the belt's fastened, it shuts off... push in the clutch, the engine can start -if not, no go, Etc. Simple binary math is all the car knows for sure. Once a condition has been met, it moves on. If it's at a certain point in the runstream, it assumes that all of the previous conditions have been met, otherwise it wouldn't be there.

Shut the car off - start all over from the beginning... just like Dragon's Lair.


But Hey - I've said my piece... sorry for the novel. And apparently, unless someone comes up with an actual answer for the problem, mine's the only recommended action that's been provided so far. Do what you will...all I ask isdon't crap on my advice when ya got nuthin' else better to try.

 

Yeah, but the SRS troubleshooting section of the shop manual is 41 pages long. The SRS system is not really user-serviceable. The OP is probably going to have to just go to the dealer. There is a way to check the SRS trouble codes, but I wouldn't recommend trying to repair the system on your own, even with the manual -- if you mess it up, the parts are very very expensive to replace.

I'm not "crapping" on your advice, I'm saying that there's nothing in the manual that implies there is ANY sort of connection between the seat belt light and the SRS system... common sense or not. Here's the circuit diagram if you want to see for yourself.

[IMG]local://upfiles/4155/A8A2AC6DEC594C9C8ED2A219858C49A2.jpg[/IMG]

 

Maybe 'crapping on' was a bad choice of words. My apologies.

The thing is (and here's an explanation why I went off on such a tangent), when I would volunteer at the base Auto Hobby Shop (it's currently closed for renovation), we'd always get people coming in asking what's wrong with their car because it's doing this or that. When myself or the certified mechanic on-duty would offer up the most likely possibilities (him more often than I, honestly), some of them would inform usthat we're wrong and that couldn't possibly be the problem. After fighting with their issues for several hours to a few days, more often than not they'd try what we suggested and it would usually solve at least part of their problem. That's what I see in some of the threads here, and other places too (it's not a localized problem in the least) -some folkscan sometimes be quick to discount someone's advice, often without having anything to offer up to actually solve the problem.

I'm not asking for an ego stroke or anything, that's not why I joined or choose to participate in these threads either. I'm just offering up what experience and knowledgeI do have. If it helps someone, bonus. If I'm wrong on a detail, or off base altogether,I don't mind people pointing it out withthe right information and abasic level of diplomacy...I can learn from others as well, and usually do - especially when I'm the n00b, and have done so countless times in these very forums. This is a great place to share information.


What my 'common sense' tells me is that if you unplug something, and a light comes on, you might eliminate the possibility that you caused the problem by plugging that something back in. It also tells me (based on my 22+ years as a computer technician) that with a connection to the ECM/PCM (based on your illustration - pin 9), there's a very good chance that the SRS unit receives some kind of a signal telling it that all's well (or something's wrong) with the systems the ECM/PCM monitors - which most likely includes the seat belt warning circuit.

Basically, ltkenbo - just plug the damn thing back in and tell me I'm wrong when the light doesn't go out after a reasonable amount of time, and I'll shut up about it.

Sorry for the drama, people - my Sudafed's been upgraded to Allegra Rx, DayQuil, and cough drops - so no, I am not a happy camper right now, coughing up what's left of my lungs (thanks be to West Texas and it's crappy air) along with everything my sinuses can produce.

 

I'm telling you, I looked through multiple sections of the manual, searching for some indication that there is a connection between the two, and I cannot find ANYTHING.

The circuit diagram for the seat belt warning (that's what it's called) shows no connection to the SRS system
The description of the seat belt warning says only that it activates a light and beeper
The SRS circuit diagram shows no connection to the seat belt switch
The SRS system description does not mention the seat belt switch
The 41-page-long SRS troubleshooting section does not say "check the connection for the seat belt switch"
Honda would not accidentally leave a critical part of the safety of the car out of (at least) five sections of the service manual.

If you can find some evidence to the contrary, I'd love to see it!

 

OK - I'm good with what you're saying. I don't have a Honda repair manual in my possession, so I won't dispute your research. And if you read my words, I'm not arguing the issue with you, either.

Ya know, the more I think about it, the more likely it is that ltkenbo probably did something else that possibly popped a minorfuse, orjittered one of the SRS cablesor something andforgot tomention it. So, whatever. He'll either fix it or not.

But- here's what I mean by 'possibly receiving a signal from the ECM/PCM.' According to your schematics in the repair manual and what you're saying, there isn't a direct 'cabled' connection between the seat belt harness and the SRS system - cool. Is the SRS system connected to the ECM/PCM? Yes - pin #9, remember (according to your schematic).

Do you know anything about data transfer and binary code bits and bytesas a computer language?

What I'm trying to say is that the SRS and the ECM/PCM communicate status codes to each other, and make decisions based on the data they share. It's the same way the ECM communicates with scan tools - that data transfer constantly updates the scan tool, so it can provide you information about what's going on with your car. For instance, if a particular sensor voltage is reading too low, it'll transmit the binary representation of the sensor voltage to the scan tool telling you what its readingis. As it goes up and comes down, that binary code bit changes. That's a complex data transfer because it's dynamic, changing constantly. A light being left on (or a seat belt sensor being unplugged) will be a simple 'On' or 'Off' bit, but is updated constantly as the computer 'clocks'.

Lookin your repair manual and tell me if the seat belt warning system (whether it be the sensor, buzzer, or any part of it) is connected to the ECM, or any of the other Control Modules (BCM, PCM, et. al.). If it is, then there's data being shared between the Control Modules, and a seat belt warning condition (for instance) is data that should be shared with the SRS system. Whether it is or not, I don't know the particulars... it just makes sense to me that the airbag system would want to know if it's functioning or not. A 'smarter' airbag system might even compensate (and go off either quicker or under lesser impact conditions) if it 'thinks' the driver isn't wearing their seat belt (or the sensor's unplugged, or something) - based on the information it's given.

I'm sorry if I went too far in the weeds for you, or insulted your knowledge by explaining something you may already know - I don't know you or your knowledge. But this is how I think of things when it comes to why the indicator lightscome on, or why the car idles higher when it's cold in the morning (theIAT sensor tells the ECU tohave the IACV open a little further to richen the mix when it's too cold). Doesn't make me think I'm a genius or anything, that's just the way all of the computer controlled systems on cars make sense to me - everything's a conditional process... just like with all electronics.

Do you at least see why I'm thinking the way I'm thinking? That's all I'm trying to accomplish here since we don't know if he plugged the seat belt sensor back in again or not - and may never find out, to be honest (especially if the SRS light went back out after he did ). Again, I don't have the manual in front of me, and yes, I find it peculiar that Honda would leave out that little nugget of information if it was the way things really worked - so I'm good with what you're saying.

BTW - did the 41-page step of the manual offer up any insight as to what he should check out instead? I'm sure ltkenbo would rather read about that than my antibiotic-induced blathering - you might want to consider sharing that with him,instead of talking to me.

Tell ya what - I'm done here. Again, sorry for the drama.

 

If you are interested, the pictures detail how to determine the fault that caused the SRS light to turn ON.

You can look up the SRS code in the service manual (http://hondatech.info/downloads/Auto/Manuals/Civic/) or post the code in this thread to get more feedback.

 

it's not connected! I know it makes sense to you that it SHOULD be, but there is not a connection.

There is nothing worth sharing because like I said before it is not really user-serviceable. RonJ just posted the very beginning of the troubleshooting section. The many pages of trouble codes all have possible causes such as "faulty SRS unit" "short to power in airbag inflator" "short to ground in airbag inflator" "increased resistance in airbag inflator" etc. etc. There's very little he could even fix at home and that's why I told him to take it to the dealer.

 

I uploaded the troubleshooting section because I thought Itkenbo might want to know why the SRS light turned ON, even if he ultimately decides to take his car to the dealer for servicing. This important information might keep the Honda dealer honest by allowing Itkenbo to question potentially unnecessary work or parts replacement. Knowledge is power.

In addition, what work Itkenbo can do at home seems largely defined by his level of expertise and his desire. Whether he tackles the job himself would likely depend on what the outcome of troubleshooting revealed. For example, in certain situations, the service manual indicates that a blown fuse could cause the SRS light to turn ON. I must assume that Itkenbo can replace a blown fuse. He may even have the expertise to replace a bad wire harness, SRS unit, or airbag, if he had proper instructions and replacement parts, and observed necessary cautions. Note that I am not telling him that he should do the work, only providing him with information that allows him to make the decision.

 

Funny - I missed that part. Whatever.

No worries.