O2 sensor

I have been having trouble with my 92 in the morning. Yeah I think that my O2 needs replaced or maybe the cat. How good I tell and how would I check my engine read out?? If the check engine light comes on how do I tell what is wrong??

This works on most Chrysler Vehicles, but the Jeeps vary from year to year, because they had a mix of technology from different companies over the years.

Turn the ignition key ON-OFF-ON-OFF-ON within 5 seconds and watch the Check Engine Light (CEL). By ON, I mean turn the key to the run position, do NOT actually start the engine. The CEL should start to blink, count the blinks between pauses and write them down. Arrange them in 2 digit numbers, and those are your codes. Do a google search for the codes, you should find a guide for you make/model/year.

It works on my '95, NOT sure about the '92, some say this works only a few Jeeps at most. Even the later Jeeps that were almost all Chrysler technology.

Code 21 is usually the O2 sensor, 21 covers several codes that would narrow down the O2 sensor problem that an OBD scanner could read.
Code 12 is "Battery disconnected within the last 50 start cycles, its common, even if that hasn't happened, don't worry about it if you have it.
Code 55 is "END OF CODES", it should be the last code you get, if its the only code you get, then you don't have any stored codes.

Advance Auto has an OBD Scanner behind the counter, if you ask, they will usually take it out to the parking lot and scan the codes for you.

That'll work on a 92 fine.

Skip

skipc said:

That'll work on a 92 fine.

Skip

Click to expand...

Works on 91 to 95, OBD1 jeeps.

There is also a Multi meter test procedure posted here somewhere by 5-90 with details on testing the O2 sensor itself, on the vehicle once it is hot.

the key on key off worked on my 96 but wont on my 00?:dunno:

00 is OBDII - you'll need a reader.

skipc said:

00 is OBDII - you'll need a reader.

Click to expand...

So is the 96 (an OBDII), interesting that they kept it in the first OBDII models in 96!

key cycling works on my 97 also.

I replaced the upstream sensor, still get a 2-1 code, so I guess the downstream one is next...

GreenJeepXJ said:

I have been having trouble with my 92 in the morning. Yeah I think that my O2 needs replaced or maybe the cat. How good I tell and how would I check my engine read out?? If the check engine light comes on how do I tell what is wrong??

Click to expand...

why do you think your having o2 or cat problems? what leads you to this conclusion?

The Key Cycling to get the CEL to flash PCM Fault Codes has been part of Chrysler Vehicles since the 80's. BUT, not 100% of vehicles over every year.

My '88 Sundance (pre-OBD), '91 Caravan(OBD-I), '99 Neon R/T(OBD-II), '02 Grand Caravan(OBD-II) all got/get codes from the Key ON-OFF cycling. So, like mentioned above, being OBD-I or OBD-II (mandated in '96 model year) compliant does NOT make a difference in being able to get the codes.

My '02 Grand Caravan with Digital Odometer doesn't flash the 2 digit codes from the CEL, it actually displays the 4 digit codes in the digital odometer.

The Jeep's sound like they were one of the exceptions for some years, but no one has really stated when they started or stopped this, once they got the Chrysler Engine Controllers. Do the 2nd Gen Cherokee's have the Key Cycling to get codes?

Rick Anderson said:

The Key Cycling to get the CEL to flash PCM Fault Codes has been part of Chrysler Vehicles since the 80's. BUT, not 100% of vehicles over every year.

My '88 Sundance (pre-OBD), '91 Caravan(OBD-I), '99 Neon R/T(OBD-II), '02 Grand Caravan(OBD-II) all got/get codes from the Key ON-OFF cycling. So, like mentioned above, being OBD-I or OBD-II (mandated in '96 model year) compliant does NOT make a difference in being able to get the codes.

My '02 Grand Caravan with Digital Odometer doesn't flash the 2 digit codes from the CEL, it actually displays the 4 digit codes in the digital odometer.

The Jeep's sound like they were one of the exceptions for some years, but no one has really stated when they started or stopped this, once they got the Chrysler Engine Controllers. Do the 2nd Gen Cherokee's have the Key Cycling to get codes?

Click to expand...

Regarding the "Key Cycling to get the CEL to flash PCM Fault Codes" it is the 1987-1990 Renix Jeeps that do not have it. I had assumed they droped it by 96 when the OBD-II came out to save money, but apparently not.