Check engine light and O2 sensors

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rmckinney

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Nashville, TN, United States
I own a 2005 Jeep Wrangler Unlimited LJ with 100k miles. The jeep runs great, but the check engine light has been on for several years now. The mechanic says that his computer codes are showing that all the o2 sensors are bad. However, he doesn't think that is the case. He thinks it's probably a computer issue instead.

Rather that wasting money on replacing possibly good O2 sensors, he's suggested I go to another mechanic that can fix the computer. The other mechanic says to fix the computer would be around $1200.

I don't want to pay $1200 just to the the light turned off. Any suggestions? Any other possible problems or fixes?

Thanks
Ryan
 
rmckinney said:
I own a 2005 Jeep Wrangler Unlimited LJ with 100k miles. The jeep runs great, but the check engine light has been on for several years now. The mechanic says that his computer codes are showing that all the o2 sensors are bad. However, he doesn't think that is the case. He thinks it's probably a computer issue instead.

Rather that wasting money on replacing possibly good O2 sensors, he's suggested I go to another mechanic that can fix the computer. The other mechanic says to fix the computer would be around $1200.

I don't want to pay $1200 just to the the light turned off. Any suggestions? Any other possible problems or fixes?

Thanks
Ryan
Click to expand...
Put your key in the ignition and turn OFF-ON-OFF-ON-OFF-ON and a code or codes will pop up on your odometer. Then come back with that code.
 
Doubtful all four O2 sensors are bad but it is possible for your two pre-catalytic converters to generate false bad O2 sensor codes. My used TJ came with intermittent O2 sensor codes and occasional misfires which ultimately proved to be bad pre-cats. I'm still running the same O2 sensors that were installed the day I bought the Jeep and no more Check Engine lights since replacing the pre-cats.
 
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Those are all o2 heater circuit codes. Have them check for power and ground at sensors. If power is missing unplug one at a time and see if power comes back, could just have a shorted heater circuit.

Seriously doubt the PCM is at fault and I'm sure all four sensors didn't fail at once.
 
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P0421
A code P0421 may mean that one or more of the following has happened:
  • The catalytic converter is no longer functioning properly
  • An oxygen sensor is not reading (functioning) properly
  • A sparkplug is fouled up

P0031
A P0031 DTC trouble code may be caused by one or more of the following:
  • A short or open in the heater circuit in the sensor
  • A failed O2 sensor heater
  • Wiring/connectors broken/frayed leading to sensor and/or relay
  • Failed PCM/ECM

P0037
Potential causes of a P0037 trouble code may include:
  • Bank 1, sensor #2 oxygen sensor heater element has failed
  • Physical damage to heated oxygen sensor has occurred
  • Control circuit (or voltage feed, depending on system) is shorted to ground
  • PCM Oxygen sensor heater driver has failed

P0051
A P0051 DTC trouble code may be caused by one or more of the following:
  • A short in the heater circuit in the sensor
  • A failed O2 sensor heater
  • Wiring/connectors broken/frayed leading to sensor and/or relay
  • Failed PCM/ECM

P0057
Potential causes of a P0057 trouble code may include:
  • Bank 2,2 oxygen sensor heater element has failed
  • Physical damage to heated oxygen sensor has occurred
  • Control circuit (or voltage feed, depending on system) is shorted to ground
  • PCM Oxygen sensor heater driver has failed


This should be easy to fix. You've got some bad O2 sensors to start. Bank 1, sensor 2 is bad, and Bank 2 sensor 2 is bad as well. It's a good idea in my opinion to replace all 4 O2 sensors while you're in there. They're cheap enough, and might as well since you're already in there.

It's possible your catalytic converters are clogged as well, but the first place to start is the O2 sensors. You can find all the information you need here: The Official Jeep Wrangler TJ Oxygen (O2) Sensor Thread

That thread has a diagram showing where each bank and sensor is located, and has all the part numbers and links for the correct NGK sensors based off what year and engine your Jeep Wrangler TJ has.
 
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rmckinney said:
i'm not a mechanic unfortunately:( Is this something I can do myself or do I need to take to the shop? If so, any idea what this work should cost? Thanks
Click to expand...

If you aren't a mechanic, I wouldn't attempt it yourself. It's going to take at least some mechanical skills, I can guarantee that.

The parts are around $160 or so, and I could do it all in about 1-2 hours in my garage. So a small shop might charge you about $400-$500 I suspect. However, my bet is that most shops are probably going to be more in the ballpark of $700 or more, mostly because they have overhead to pay and employees.

It's not that difficult of a job at all though, it really isn't.
 
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Chris said:
So a small shop might charge you about $400-$500 I suspect. However, my bet is that most shops are probably going to be more in the ballpark of $700 or more, mostly because they have overhead to pay and employees.
Click to expand...

So they are not honest because they have overhead and employees? :BangHead:

The average shop would charge around
$100-150 diagnostics
$350-400 parts
$200 labor
Based on the replace all 4 sensor scenario

That's $650-750

Tech pay =$80
Parts cost =$160
That's 55% gross profit to pay rent,heat, insurance, support staff, owner, tools, equipment etc. Most shops net 8-10% profit after all that.

10% of the hypothetical $750 is $75.00
So glad I r a mekanick. Getting rich quick.
 
My bad... wrong choice of word on my part. I edited the original post. I’ve had very, very bad luck with shady mechanics in the past, as has my family.

I meant to say that I know guys who are mobile mechanics or work out of a tiny space and would charge a lot less because of that. But I guess that makes sense.
 
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Jerry Bransford said:
Doubtful all four O2 sensors are bad but it is possible for your two pre-catalytic converters to generate false bad O2 sensor codes. My used TJ came with intermittent O2 sensor codes and occasional misfires which ultimately proved to be bad pre-cats. I'm still running the same O2 sensors that were installed the day I bought the Jeep and no more Check Engine lights since replacing the pre-cats.
Click to expand...

Jerry - This makes sense but would there be other symptoms of a clogged cat, like loss of power and misfires? The OP did not describe these symptoms so could this be a little build-up in the pre cats? OP, any other symptoms?

OP - I have a 2005 LJ with 95k miles, and have had my four O2 sensors go off every summer when it is excessively hot outside, I get codes 0032/0038/0052/0058.

I changed all four O2 sensors and no luck at all. Everything I have read on the crazy internet points to a faulty PCM, including a post on the other wrangler forum with your four codes and the end result was a faulty PCM.

This past summer I failed emissions and had to go back when it got cooler outside in order to pass. The test center kept the Jeep for a few days as they were now curious, and confirmed the PCM was bad. They recommended going through a dealership since the dealership would warranty the new part.

Problem is they do not make new PCMs. They sell refurbished ones so you might get someone else's problem. If your Jeep is running fine and only throwing those codes once in a while I would let it be and do not throw money at it.

When my local dealership wanted $950 to install a refurbished PCM, and they agreed it was the main problem, I passed.
 
skrelnik said:
Jerry - This makes sense but would there be other symptoms of a clogged cat, like loss of power and misfires? The OP did not describe these symptoms so could this be a little build-up in the pre cats? OP, any other symptoms?
Click to expand...
My cats weren't clogged when I just getting the Check Engine lights and O2 sensor codes. The clogged main cat came much later after one of the two bad precats came apart inside and its insides blew out and down into the main cat clogging it.
 
guys,
I took my jeep to a 3rd mechanic, he read the codes and he's suggested replacing all 4 O2 sensors and the 2 catalytic converters. $950.

The 1st mechanic I took it too, thought the problem would be a bad PCM. He's suggested I take it to a different mechanic shop that was better at diagnosis complex problems. My 1st mechanic didn't feel comfortable replacing the 02 sensors and 2 cats, then the problem be the PCM or vise versa.

The 2nd mechanic wants $150 to diagnosis the problem. (I've passed on that for now).

Suggestions?
 
rmckinney said:
guys,
I took my jeep to a 3rd mechanic, he read the codes and he's suggested replacing all 4 O2 sensors and the 2 catalytic converters. $950.

The 1st mechanic I took it too, thought the problem would be a bad PCM. He's suggested I take it to a different mechanic shop that was better at diagnosis complex problems. My 1st mechanic didn't feel comfortable replacing the 02 sensors and 2 cats, then the problem be the PCM or vise versa.

The 2nd mechanic wants $150 to diagnosis the problem. (I've passed on that for now).

Suggestions?
Click to expand...

I would recommend resetting your PCM and see if the codes come back.



1. Disconnect the battery by removing the Negativebattery cable (This will ensure that any possibility of grounding the power side to the vehicle [or yourself - think wedding ring] does not happen.)

2. Disconnect the Positive battery cable

3. Allow a few moments to pass before reconnecting the cables

4. Reconnect the positive cable to the battery

5. Reconnect the negative cable to the battery

6. Turn the Vehicle on
 
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