02 sensor code

[LilRedRover]

Here's the lowdown

99 Sport
4.0 approx 112k

Check engine light came on today so I took it to autozone to have the codes read. Guy said something about it's reading like my "board", whatever that is, is sending too high of voltage to my 02 sensor... I know quite a bit about jeeps and I have no idea what this guy is talking about. Anyone else interpret this from idiot language to something useful?

[fdsa487]

Originally Posted by LilRedRover

Here's the lowdown

99 Sport
4.0 approx 112k

Check engine light came on today so I took it to autozone to have the codes read. Guy said something about it's reading like my "board", whatever that is, is sending too high of voltage to my 02 sensor... I know quite a bit about jeeps and I have no idea what this guy is talking about. Anyone else interpret this from idiot language to something useful?

Sorry I can not help much on this subject but my engine light is also on. Took it to autozone and they said 02 sensors were ALL disfuncitional. I had like 3 or 4 different codes read out on the computer unit. BTW 2000 sport. I6

[jeepdude10000]

i would say that your O2 sensor is bad or on the way out, if you get over voltage means there's something wrong.

[RAVC1]

LilRedRover,

You need the number of the code; like P0138 - Sensor Circuit High Voltage. I have replaced both front and rear O2 sensors in the last year (~20k miles) on my '97 XJ Sport. Parts stores like Murray's & AutoZone will let you borrow a generic scan tool so you can see the code or codes yourself. You just have to leave your driver's license with the cashier to take the scan tool out of the store and into the parking lot to use it.

In both situations my engine exhibited a driveability issue called "surge." You feel power, then a loss of power and the cycle repeats itself and the engine may not get out of this operating mode. You vehicle may be setting O2 codes for completely different reasons.

Rick

[LilRedRover]

Originally Posted by RAVC1

LilRedRover,

You need the number of the code; like P0138 - Sensor Circuit High Voltage. I have replaced both front and rear O2 sensors in the last year (~20k miles) on my '97 XJ Sport. Parts stores like Murray's & AutoZone will let you borrow a generic scan tool so you can see the code or codes yourself. You just have to leave your driver's license with the cashier to take the scan tool out of the store and into the parking lot to use it.

In both situations my engine exhibited a driveability issue called "surge." You feel power, then a loss of power and the cycle repeats itself and the engine may not get out of this operating mode. You vehicle may be setting O2 codes for completely different reasons.

Rick

see, that's what is weird... my engine isn't exhibiting any weird behavior. It is driving like it always does, but with the check engine light on. Last night I took the wife to dinner and when we came out of the restuarant, the check engine light wasn't on anymore. I am wondering if it has something to do with the heat.

[RAVC1]

LilRedRover,

It is possible the engine operating condition that set the code has not been observed. The difficutly I'm having with your experience is that codes, or DTCs, are permanent until you "Clear Codes" with a scan tool.

Also, just because my '97 exhibited driveability issues does not mean yours will. Cause and effect are much more complicated than this.

It is a little more abstract than this but not much.

Rick

[LilRedRover]

yeah I understand... I am wondering if when the guy scanned it yesterday afternoon he cleared the codes and it was a "ghost code" if you will and when he cleared it and I went home the engine wasn't off long enough to clear the system and then it was off for 2 hours while at dinner and it had time to clear.

[UNCC_99XJ]

I've been chasing this same problem on my 99 since March. Every damn time that light comes on, everything is running fine. And every time I hook a DRO up to it and pull the voltage readings while the engine is idleing, all the sensors check out just great and react accordingly with throttle input.

The only time it really flipped out was in April while I was at Spring Break at the beach. Was driving down the road and the light came on. Drove it to the nearest autoparts store and pulled the code, and got the same flippin one, P0138. On the way back from the store (happened to be an autozone) it started flippin out on the highway, wouldn't hold a gear, and wouldn't idle worth a damn either. Pulled off and let it sit a couple of hours on the side of the highway, and managed to limp it back to the beach house which was a good 5 miles away still. The next day I took it out and drove it up and down the island a couple of times, and even on the beach, with no problems. The CEL came on and off a couple of times on its own, but everything ran great, and it wasn't running rich at all.

Long story short I got it the 200 miles home and turned the light off (also pulled a code for the TPS which would explain the flippin out on the highway, as well as some tranny code that apparently can only be pulled with a special scanner for the AW4.). The o2 sensor code has come up only once since then, and the others havent come back up at all (still not sure why they did to begin with). Im not replacing the damn thing untill I can catch it acting up, to be absolutely sure its the sensor thats the problem. MPG hasnt suffered, and has actually got better since i put my flowmaster on (went from 14-15 all city to on average or 16-18 all city)

[LilRedRover]

well looks like I won't do a damn thing until it's needed either then... black electrical tape over the check engine light and I'm good to go