Still have check engine light after replacing O2 sensors

[DharmaDog]

So a couple of months ago I posted here about a problem with hesitation and my check engine light being on. The computer was throwing 3 O2 sensor codes (132, 135, 138, IIRC). So I replaced the front sensor because the rear one had been replaced the previous year. I used a Bosch from AZ. Problem did not go away. I took it to the dealer and they said I must have a bad O2 sensor from Bosch and I should use the OEM. Coincidentally, the rear O2 sensor got one of its wire snagged and ripped about this time, so I replaced both with OEM sensors. Also did not solve the problem.

The XJ hesitates only after it has been sitting for as little as 5 minutes. It will only do it once until it is shutdown again and started back up. It always does it within the first couple of blocks of driving and usually before I have a chance to get the RPMs up. When it hesitates it is also "backfiring" for lack of a better word. There are loud pops coming from the exhaust and it feels like they are coming from near the front of the vehicle rather than the back. I can also hear an exhaust leak now. Not sure where it is coming from.

The strange thing is that it passed emissions while it had these problem just a couple of months ago. Could the exhaust leak be the source of my problems? Any other ideas?

 

[DharmaDog]

Forgot to mention that I have also replaced the cap, rotor, wires, plugs and cleaned the TB. I went back to all OEM stuff for the replaced parts.

 

[jneary]

i cant recall when hey had it, but i think yours does. check the fuses under the hood, one should be for the o2 heater circuit. that would explain the check engine light if one of the faults is for o2 sensor heater failure. this usually happens when the rear sensor comes in contact with the driveshaft and rubs or rips out the wiring.

 

[lobsterdmb]

After I changed mine, I had the same problem. I unhooked the battery for 5 or 10 minutes and when I reconnected it and started the jeep, the light was off. I think the computer needs to be reset.

John

 

[DharmaDog]

I've already reset the computer twice. Once by disconnecting the battery and another time with a scanner tool at a local shop.

 

[imma honky]

You dont mention your year (or im skipping it) I know on pre ODBII vehicles there is an emissions timer. Set for 80k miles. You either replace it or have it reset by a DRBII? scanner at the dealer. Mine is/has been on since I bought it in jan and ive replced the 02 sensor. I know its new, so i pay it no attention.

 

[jneary]

You dont mention your year (or im skipping it) I know on pre ODBII vehicles there is an emissions timer. Set for 80k miles. You either replace it or have it reset by a DRBII? scanner at the dealer. Mine is/has been on since I bought it in jan and ive replced the 02 sensor. I know its new, so i pay it no attention.

yours is a 1990, and you have an emissions timer. it is located under the dash attatched to the knee bolster on the driver's side.it is there just so the customer is reminded to have the emissions system checked as routine maintenance. it is a tinted clear box and if you just unplug it the light will go out. the other alternative is to replace the timer, but why bother at this point especially if you replaced the o2 sensor.

 

[imma honky]

yours is a 1990, and you have an emissions timer. it is located under the dash attatched to the knee bolster on the driver's side.it is there just so the customer is reminded to have the emissions system checked as routine maintenance. it is a tinted clear box and if you just unplug it the light will go out. the other alternative is to replace the timer, but why bother at this point especially if you replaced the o2 sensor.

Echo?

 

[jneary]

Echo?

i was just telling you how to turn the light off, you said your light was stil on

 

[DharmaDog]

Sorry. It's a 1998 Classic. I haven't been to this forum for a while. It used to put all the info about my XJ at the bottom. Guess it doesn't do that anymore.

 

[Kejtar]

Sorry. It's a 1998 Classic. I haven't been to this forum for a while. It used to put all the info about my XJ at the bottom. Guess it doesn't do that anymore.

Did you pull the codes? are they the same codes as before? new ones? It is possible that you got a bad sensor and it's still triggering. Also look at your wiring and make sure there are no rips and that the contacts are clean.

 

[DharmaDog]

Yes, the codes are the same according to the dealer. I have a hard time believing that 3 front and 2 rear O2 sensors have been bad. The wires are fine. If my exhaust manifold is cracked (don't know that it is) could this cause the codes? I believe the engine is running rich. The O2 codes are annoying, but the hesitation and exhaust popping is what has me worried. Sometimes it tries to die at lights after being started. It lurches forward as it revs higher to keep itself going. Once I get on the throttle the problem goes away until the next time I shut the engine off and restart it.

What about the TPS? Could this be the problem?

BTW, I looked for the O2 heater fuse, but did not find one labeled as such. I will consult the FSM.

 

[jneary]

are the 132,135,138 current codes. i went on the chrysler tech web site and there are only 132, and 138 for the 1998 xj
the 132 says tps does not agree with map sensor, which basically means the reference voltage isnt reading the same for both sensors. when we see this fault the majority of the times the tps is bad.
the 138 is target idle not reached. possibly from bad tps reading.
this could also explain your problems.the tps should read 0% at idle. if it is higher check your connections, if ok probably bad tps

 

[DharmaDog]

jneary,
I'm not sure what to make of that. I don't remember what exactly I used to determine what the codes meant, but both the dealer and I found the codes to be O2 sensor codes. Definitely got the three codes that I mentioned as well, plus one in the 400 range (461, I think)

 

[jneary]

well you need to know exactly what the codes are and their description or all we can do is speculate.

 

[DharmaDog]

I know the codes are 132, 135, and 138 as far as the O2 codes go. I already said that. There should be no need to speculate on those.

I was guessing on the last one in the 400 range, but it doesn't likely have anything to do with this. I found the notes I took at the time and it is 436, not 461. It pertains to the fuel sensor.

 

[jneary]

what were the descriptions for the faults.

 

[jneary]

ok i found it on alldata sorry for the mix up.
132 is upstream shorted to voltage--- basically the pcm sees 5 volts and nothing is returning from the o2 sensor, like it is unplugged or possibly an open circuit between the o2 and the pcm. if all wiring has continuity, probably a bad pcm.
135 is upstream o2 heater failure. possibly the pcm not seeing the heater. could be related to the 132. or a blown o2 heater fuse.
138 is down stream shorted to voltage. same diagnostics as 132 except for down stream.
if the o2 sendsor shorted to the driveshaft when the wiring came loose. it could have shorted the pcm if no fuses are blown for that circuit.

 

[DharmaDog]

OK, I found the descriptions.

132: Upstream O2S Shorted to Voltage. Oxygen sensor input voltage maintained above the normal operating range.

135: Upstream O2S Heater Failure. Upstream oxygen sensor heating element circuit malfunction.

138: Downstream and Pre-Catalyst O2S Shorted to Voltage. Oxygen sensor input voltage maintained above the normal operating range.

463 (not 436 as above): Fuel Level Sending Unit Volts Too High. Circuit shorted to voltage between PCM and fuel gauge sending unit.

 

[jneary]

as far as the fuel level ..it means that the pcm saw 5 volts on the fuel level circuit , possibly unplugged with key on open it the 5 volt reference wire between the pcm and the fuel level sender. the 98's had problems with the fuel level sensors, some were even recalled. that could be that problem