jeep wrangler 94

[butch48]

service engine light comes on.
some say just drive it that way, but it will not pass inspection that way.
runs great , 4 cyls. w/ 104,000 miles.
any ideas........help.

[myjeepsux420]

Go to Autozone and have them pull the codes from the pcm. Tell us what they say and we'll be able to tell you how to fix it. It's free @ Autozone to get the codes pulled.

[butch48]

Originally Posted by myjeepsux420

Go to Autozone and have them pull the codes from the pcm. Tell us what they say and we'll be able to tell you how to fix it. It's free @ Autozone to get the codes pulled.

Houston we have a problem!
My code reads 3-6-3-8-1-0
Autozone says it must start w/ one or two letters as a prefix.
fyi, I disconnected the battery, thinking that would reset the computer, no such luck.
Any ideas...............thanks,
butch

[fredjacksonsan]

1st thing I would check would be the gas cap. If it's not sealing, the check engine light will come on.

[butch48]

Originally Posted by fredjacksonsan

1st thing I would check would be the gas cap. If it's not sealing, the check engine light will come on.

Hey Fred, I narrowed it down to the code 36 [from 363810]

It says, the pcm has determined that a malfunction exists in the heater control circuit for oxygen sensor 2 in the bank. [oxygen sensor 1 is the closest to the cylinder head. before the catalytic conveertor, while oxygen sensors 2 and 3 are located further downstream and are typically mounted in or after the catalytic converter] [ bank 1 identifies the location of cylinder #1, while bank 2 identifies the cylinders on the opposite bank].

I can only spot the first one, and not the second and third.

Thanks butch.

[fredjacksonsan]

Sounds like an extended search under the vehicle, in 10 degree temps with the wind howling is in order. (That's when I usually have to crawl around under there searching for something)

Once you find it, should be a pretty easy replacement.

[94 Jimmy]

The O2 Sensors have to be around 600 degrees to operate properly. Most cars now have heaters built into the sensors to get them up to temperature more quickly. Your PCM has detected that the heater circuit is not functioning properly and has set a code, probably because the heater in the sensor has burned open.
Generally O2 sensors should be replaced every 50K Mi, letting them go longer usually affects the engine efficency and mileage.
Sensors infront of the CAT are used to control the mixture and on a 4 banger I would imagine there would only be one of them. The sensors behind the CAT only checks the CAT operation.
If you haven't done so by now, I'd change the offending #2 sensor and the #1 sensor also. If it's a little expensive ($50 each) then move the #1 to the #2 position and put a new one in the upstrean side.
See ya
94

[butch48]

Originally Posted by fredjacksonsan

Sounds like an extended search under the vehicle, in 10 degree temps with the wind howling is in order. (That's when I usually have to crawl around under there searching for something)

Once you find it, should be a pretty easy replacement.

Fred, I'll wait. Fort Worth weather is 80 on sat.
Called Autozone, 42.00 dollars for a sensor, not bad.
Thanks to all for the help..............Butch.

[butch48]

Originally Posted by 94 Jimmy

The O2 Sensors have to be around 600 degrees to operate properly. Most cars now have heaters built into the sensors to get them up to temperature more quickly. Your PCM has detected that the heater circuit is not functioning properly and has set a code, probably because the heater in the sensor has burned open.
Generally O2 sensors should be replaced every 50K Mi, letting them go longer usually affects the engine efficency and mileage.
Sensors infront of the CAT are used to control the mixture and on a 4 banger I would imagine there would only be one of them. The sensors behind the CAT only checks the CAT operation.
If you haven't done so by now, I'd change the offending #2 sensor and the #1 sensor also. If it's a little expensive ($50 each) then move the #1 to the #2 position and put a new one in the upstrean side.
See ya
94

Jimmy, i'm still getting good mileage. and it runs well.
My troubles started when I had no heat, I changed the thermostat.
I now have great heat, but a service engine lite.
FYI I disconected the battery, thinking that would reset the system, no luck. Thanks for the great explanation about sensors. Ill do it.,,Butch.

[fredjacksonsan]

Good info, 94 Jimmy.

[butch48]

Originally Posted by fredjacksonsan

Good info, 94 Jimmy.

Fred, I found a fountain of info on jedi.com
Thanks to all Butch.