Sensor light

[Kegomatix]

My buddy (well rather a buddy of a buddy) took the 720 mudding in my back field. It sounded like he had it pinned down at redline the entire time.... 

 

Anyhow, the sensor light kicked on but it doesn't seem to be running any different. I can't imagine there would be too many possibilities on an 86, and the 02 sensor was replaced pretty recently. Could it be anything else or is it pretty much only tied in to the 02 sensor?

[datzenmike]

I didn't know the 720 even had a sensor light in the dash. Could it be the charge light? What does it say?

 

Most EFI  models have a 'check engine' type light to warn that the computer has picked up some kind of sensor/emission type problem. If this was just a brief 'spike' that set it, disconnecting the battery briefly will reset it. If the problem is permanent it will come back.

[izzo]

85 and 86 does have a sensor light, 84 might.

 

usually its the 02 sensor, or something to do with the emissions, carb.

[datzenmike]

Yeah I have an '84 FSM and I don't see it.  Correction I found it to the left of the bat and above the 4x4 on indicator. Can't find anything on how it is turned on.  Disconnect battery and see if it comes back on later.

[Kegomatix]

Thanks for the replies. Yes it's next to the battery light, says sensor. I've disconnected the battery for over 30 minutes and it came back. Is there any way to tell if the 02 sensor is bad other than just replacing it?

[izzo]

Notice it running funny? Any smoked out the exhaust, or smell like its running rich? 

Better question, do you have the stock carb or has it been replaced with a weber?

[Kegomatix]

Nope, it seems to be running exactly as it did before the light came on, which is really well. And it has the stock carb.

[datzenmike]

Well you can unplug the larger 20 pin connector to the ECU under the driver's seat and check the continuity from it to the O2 sensor on the exhaust manifold. Disconnect the O2 sensor and ground the wire to the exhaust manifold. On your ohm meter place the + lead on the #2 wire in the ECU plug and the - lead to ground. If the wire is good you should read o (zero) ohms.

[DREWSDIME]

My sensor light is also coming on but after a few revs of engine it goes away and after light goes off immediately I hear a buzzing/whining noise coming from engine bay cant pin point it I thought it was water pump but I replaced that today and still no luck

FML alt belt came off pulley on way home tonight , luckily it was still there somehow just missing some teeth I was able to get it back on pullies and as I was tightening the top alt bolt I snapped off the head F#@K!  Luckily I was only a few miles from home and was able to drive home and somehow belt stayed on :thumbup:

[MikeRL411]

_{Mechanical Alternator voltage regulator?}

[datzenmike]

Naw, all alts. after '78 were internally regulated.

[wallaccx]

I think the Sensor light has to do with the temperature of the catalytic converter.  I've had a couple of old European cars in my day, and their Sensor light was tied to a thermal switch in the floorboard above the cat.  Driving too hard would overheat the catalyst and cause damage-- ignoring it could cause a fire.  Seems like I read somewhere that the Sensor light in the 720s are supposed to stop reading after 100,000 miles, which is the service life of the cat.

[datzenmike]

Yes there is a floor temp sensor on some trucks. California 620s come to mind but could be wrong.

[datzenmike]

OK

 

Here is what the sensor light means, how it operates and how to 'service' it.

 

 

by Mike Cieply:

 

The sensor light is a maintenance reminder. It is programmed to come on at 50k and 90k, at 60 k you are supposed to check  the 02 sensor and replace if needed, after that, there is a one wire connector (believe the wire is brown) under the cluster (below clock under the dash) you take it apart and swap it to the other one wire connector, it will go off until 90 k, check o2s again and replace if needed, then disconnect the connector entirely and the light will never return ( this is per the Nissan FSM) 

 

 

My 76 710 a counter like an hour meter (so do similar year cars and trucks) on the pass side that sets off a warning lamp to remind you to clean and service your EGR valve.

[85 nissan]

 

I took this pic today, but my questions its for how long needs to be disconnected? and the relay location

 

 

 

[bryant2482]

this is crazy to me. i dont think swapping the wires has ever been done on my truck

[izzo]

^^ I'd be surprised if they were changed in any truck other than some old man buying one new and actually taking care of it. I'd put money on the sensor light is burned out or removed in 99.9%

[Jdm720]

Huh, this is all new info to me. 

 

I have the sensor light in my '84. A week or two ago i was swapping out some of the dim cluster lights and noticed the SENSOR bulb was missing. Installed one and it lit right up. Stayed on, too. 

So I just took it right back out....

[datsunaholic]

I took this pic today, but my questions its for how long needs to be disconnected?

 

After 90,000 miles?  Forever.

[bryant2482]

i was going to work this morning and for the first time my sensor light came on. i just came home and the light is off. what would cause that to happen? because ive been reading on this now, it says it comes on at 50k and 90k. it doesnt make sense since i have just over 124xxx on mine

[720Girl]

Can someone please tell me why I can't see any photos in any thread?!

[Crashtd420]

Can someone please tell me why I can't see any photos in any thread?!

Because photobucket sucks.....

Started charging to host....

If you have a computer there are fixes to view... but I have no idea about it... I use my phone....

[MaxChlan]

Here's the definitive answer to the sensor light from the 86 FSM:

 

[Toxicrain]

My 85 has a sensor light and a couple inches down the wire there is a tag saying i think something about seat sensor and it turns on after 90k and then you reset your battery and then it turns on after another 60k and then your supposed to unplug it which i did when the light came on and havnt had an issue with it since.

[Charlie69]

Easiest fix is to remove the bulb if it bothers you.