88 S4 N/A...Where is the "Heat Hazard Sensor" as stated in the FSM....

In the section for Emissions it shows a drawing of the Heat Hazard sensor....I did a search and it did not come up.....also...the dealer does not have it listed but it is in the FSM in 4A-47 .....help if you can.....thanks....

 

Harley, what kind of silly idea are you coming up with now?

You can check the sensor from the ECU. Actually, it's just a switch, IIRC...

You know, all of those times I've crawled around under my car, I've never seen it, lol...Probably because I wasn't looking for it...I would GUESS somewhere around the main cat area, up above the heat shields...

You think this is part of your no-start thing?

 

It's inside the car, under the carpet on the passenger side floor.

 

buttsjim....thanks for that.... no wonder I could not find it....now....what does that sucker do ? would it shut anything down if it were to malfunction, say on an intermittent basis....is it on the angled part of the floor or flat on the floor...thanks

 

It's on the flat part of the floor, just in front of the seat, as I recall. You have to pull the carpet back and then wedge something under the carpet it to hold it up out of the way.

You've exceeded my limited question answering ability with your question about what it does. I think it opens the relief solenoid valve for the cat's secondary air injection, but I'm not sure.

 

You have done a great job thusfar Jim....your best guess....could a malfunction cause the car not to start....theoreticall...by the secondary air injection system not getting the right signal or a short in the curcuit ? just your opinion.....thanks much....

 

OK. This IS a guess, but I don't THINK a malfunctioning heat hazard sensor would have any noticable affect on performance, or your car's ability to start.

I just looked at the FSM and see that the sensor is discussed on pages 4A-34 and 4A-35, so you might check that to see what you think. Or, wait for someone who knows what he's talking about to reply to this question.

 

OOOpps.....there is nothing on the floor, in front of the seat on the passenger side....do you mean the driver side, possibly?

 

Passenger side, its used to detect excessive exhaust temps.

 

No, the passenger side. I almost didn't reply to your original question, because my experience is exclusively with the Turbo II. But, I checked the FSM for the n/a (it shows it) and both models have cats, so I was pretty sure your car was the same as mine in that respect.

The sensor should be about 6" in front of your seat rail, passenger side, and closer to your transmission tunnel than to your door sill. You may need a flashlight to peek under your carpet and see it. If it's not there, I sent you on a wild goose chase, and I' truly sorry for that.

 

I think about the only things it does are 1) put on the warning light, and 2) kill the split air going into the cat by way of activating the ACV's relief valve function...

Notice I said "think", Hailers...Although you can jump in anytime to correct me, I'm used to it by now

 

Ok....maybe it won't affect a start up...but until I find out for sure I have to believe it is at least possible that anything to do with air flow can have repercussions on whatever....
buttsjim....your input is fine...no problem dude....these things are not an exact science and I really do appreciate your help....I'm going in the right direction....thanks again...

 

Reviving an ancient thread...because I search before I post. So does anyone know if this sensor affects in any way the engine's air flow or the air/fuel ratio? My car is S5 turbo.