Where to start???
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Where to start???
Hi everyone. I have a 94 Explorer 4.0 4x4 from which I pulled the following codes:
176 & 177 (HEGO indicates lean/rich on bank 2). Do you think it's a bad o2 sensor or something else. Which side is bank 2 (one list said "front side.")
MY CEL comes on after about 80 miles of highway driving and stays on for about 20 secs, goes out for 20 seconds, over and over until I shut it down.
Start it up the next day and it's fine. CEL never comes on just driving around town. Another thing, when CEL has been going on/off and I let it idle, it idles rough and I think I even smelled something burning from around the driver's side frame rail back near the gas tank. Thanks for any and all suggestions about where to start.
176 & 177 (HEGO indicates lean/rich on bank 2). Do you think it's a bad o2 sensor or something else. Which side is bank 2 (one list said "front side.")
MY CEL comes on after about 80 miles of highway driving and stays on for about 20 secs, goes out for 20 seconds, over and over until I shut it down.
Start it up the next day and it's fine. CEL never comes on just driving around town. Another thing, when CEL has been going on/off and I let it idle, it idles rough and I think I even smelled something burning from around the driver's side frame rail back near the gas tank. Thanks for any and all suggestions about where to start.
Postmaster
Joined: Dec 2001
Posts: 3,742
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From: UT
I think 176/177 refer to the left/drivers side O2 sensor (the one in the driver's side exhaust manifold). From my code list, 176 is a lean code, 177 is a rich code (an interesting contradiction).
1st question for you: Can assume these are memory codes? Did it pass the KOEO test (111 for the first set of codes during the KOEO test)? Did you try the kOER test? If so, did it pass, or did you get a 136/137 from the KOER test?
A couple of ways to approach O2 sensor codes. You could simply replace the O2 sensor (especially if it's been in there a while), and if that doesn't fix the problem, diagnose more thoroughly. I think I would at least make sure there are no obvious wiring faults or fuel pressure issues before simply replacing the sensor.
1st question for you: Can assume these are memory codes? Did it pass the KOEO test (111 for the first set of codes during the KOEO test)? Did you try the kOER test? If so, did it pass, or did you get a 136/137 from the KOER test?
A couple of ways to approach O2 sensor codes. You could simply replace the O2 sensor (especially if it's been in there a while), and if that doesn't fix the problem, diagnose more thoroughly. I think I would at least make sure there are no obvious wiring faults or fuel pressure issues before simply replacing the sensor.
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Thanks for the reply. It did pass 1-1-1 KOEO, then gave the 2 codes. KOEO test only showed 536 (I think) or BOO test was not performed. I did the WOT test and I guess it was fine. Cylinder balance test was 9 (pass) and also 9 when repeated so It's not a bad injector or plug as I had thought. As far as I know, all the o2s are original, so they could be going bad after 115k miles. Dealer told me it was a bad module and they could replace it for $800. I almost died. They also said my ABS light and the CEL were both caused by the same bad module (I didn't see how that could be!) I replaced the ABS electronic control relay for about 5 bucks and it has worked ever since. I have had trouble with just about every relay in the box going bad over the past 6 months, but replacing them has worked fine... except for the ecm maybe?? Anyway, thanks for the reply.
Posting Guru
Joined: May 2002
Posts: 1,574
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From: Phoenix
First - never go to a dealer.
Second - come here and ask us. Those that own these vehicles and work on them and have had the problems you do now have. Those of us that give a Shi t about helping our neighbors and not just taking their money.
So let me **** off the obstinate ones and say - " go buy 2 new O2 sensors" Replace both sides and also clean the MAF sensor. Find out how here http://draco.acs.uci.edu/explorer/
Do this. Disconnect the battery for 5 minutes to clear codes and the learned correction factors out of the PCM/computer.
You might have addition issues like bad wires/plugs...
Before you do any of what I have suggested, you may want to pull the plugs too and see what they say. A black one is too rich, a white one is too lean. This will help you understand what is going on inside the motor - forget the computer. What are the hard facts?
Second - come here and ask us. Those that own these vehicles and work on them and have had the problems you do now have. Those of us that give a Shi t about helping our neighbors and not just taking their money.
So let me **** off the obstinate ones and say - " go buy 2 new O2 sensors" Replace both sides and also clean the MAF sensor. Find out how here http://draco.acs.uci.edu/explorer/
Do this. Disconnect the battery for 5 minutes to clear codes and the learned correction factors out of the PCM/computer.
You might have addition issues like bad wires/plugs...
Before you do any of what I have suggested, you may want to pull the plugs too and see what they say. A black one is too rich, a white one is too lean. This will help you understand what is going on inside the motor - forget the computer. What are the hard facts?
Posting Guru
Joined: May 2002
Posts: 1,574
Likes: 1
From: Phoenix
Backin is riding this PCM failure thing which I do also believe is now becomming an issue. I now have a back up PCM in my garage just in case. But before we go off buying a new one, we need to make sure the inputs and outputs and all the components are working correctly. A PCM replacement would be a last resort.
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