P0138 Code Problem

[aafxsniper]

I have a problem with my 01 SL sedan. About a month and a half ago, I broke the rear O2 sensor while doing exhaust work. Of course the light came on. I changed it last week and cleared the code, and it came back half a day later. I figured I'd gotten a bum sensor so picked up another. Cleared codes again, guess what? Code came back. Grrrrrr. I've never had any problems with the car except that the mileage seemed a little, well, not as good. It's the only code the car has ever thrown out. I'm confused to why I get this now and can't get rid of it. I have noticed that the oil has fuel in it, not dangerous amount, but you can smell it from the dipstick. I'm doing an oil change but would like to find the source of the problem first. What could cause it and not give a code??

[OldNuc]

Exactly what brand and type/part number did you replace the sensor with?

Did you try and clean or grease the rear O2 sensor connector?

If it is responding correctly then it is confirming a rich condition downstream of the CAT.

[aafxsniper]

It's a Bosch.. OE not a universal. Second one so it isn't the problem. The car is running rich but I don't know why. It's only giving the downstream code..

[fdryer]

Coolant sensor may be at fault causing the rich running condition. As a newbie you'll need to read about it if yours has the original resin tipped sensor. Replacing it with the brass one fixes the issue permanently. Use the Forum Jump below to find the How-to library about it. Buy it from any auto store.

[OldNuc]

The rich operation is why you are getting the code. If you have not replaced the ECTS that is the first thing to do. Then the spark plugs must be NGK BKR4ESA-11 for the SOHC or BKR5ESA-11 for the DOHC. Also, get a new set of plug wires. Mid priced direct fit set will be fine. If your present wires are less than 6 months old they should still be good and do not need replacement.

The how to info is located in the How-To Forum. Take the forum jump at the bottom of this page and select the How-To Library. The first 3 sticky posts contain the video index and links to the richpin videos and the other 2 describe the ECTS replacement in detail. Be sure to carefully inspect the ECTS connector for any sign of corrosion or moisture.

The new ECTS may be purchased from any auto parts store. The NGK plugs may be located at Advance Auto

[aafxsniper]

Hmmm, funny thing. I replaced the plugs and wires in June. Both NGK from Saturn. It was all fine til I broke that damn O2 sensor. I ordered an ECTS the other day, but a new problem developed...not really new, but.....Back in May my car would "shut down" randomly while slowing down. Everytime this happened the stereo would reset. Memory would disappear. I thought I had solved this by getting rid of the amplifier wires that were put in the car. Today it happened again. Shut down twice today for no apparent reason. No codes are showing for this. I've checked all wires under the hood and it all looks fine. Nothing is grounding out or bare. It doesn't matter if I'm on a bumpy road or turning sharply, there is no rhyme or reason to this problem. I'm starting to get a little pissed at this point....

[OldNuc]

That shutdown problem is most likely a overheated connection at the back of the interior I/P Panel caused by the continual overload caused by the departed amplifier. Its on the black connector at the front end of the panel on the back.

Local parts store sells the ECTS. As soon as you change it out you will know if the problem is fixed. Be sure that you very carefully inspect the ECTS connector for any signs of moisture or corrosion when you are changing it out.

Your temperature gauge should read 3/8 when the engine is warm and you are driving at 35-45mph with the A/C off. If it does not then there are more problems.

[aafxsniper]

I/P panel??? What and where? The amp was hooked up professionally, I disconnected the wires at their sources, one to the battery, one to the column and a body ground. I'm not sure if it's the Instrument Panel you're referring to, but there was nothing hooked into it. I may sound a bit stunned, but could you be a little more specific on this I/P please...

[fdryer]

Originally Posted by aafxsniper

.....Back in May my car would "shut down" randomly while slowing down. Everytime this happened the stereo would reset. Memory would disappear. Today it happened again. Shut down twice today for no apparent reason. No codes are showing for this..... It doesn't matter if I'm on a bumpy road or turning sharply, there is no rhyme or reason to this problem....

Radio memory and engine shutting down randomly all points to main power - battery and battery cables. Looking isn't everything if there's a hint of corrosion on the battery connections, starter, main ground and alternator fusible link connection. If you have to, remove the battery cables for an up close visual to see if corrosion from a leaking side terminal from the battery RED positive post damaged the battery cable; peel back the heavy insulation if you need to reveal the extent of acid eating away copper wires and leaving a loosely crimped terminal that makes poor connections. You're either on the original or second battery and most likely on the original battery cables. Check by pushing/pulling/tugging all main power wires to the starter, alternator, and ground to be sure none are loosely connected especially main ground (for corrosion). Remove connections for cleaning if necessary.

[OldNuc]

Originally Posted by aafxsniper

I/P panel??? What and where? The amp was hooked up professionally, I disconnected the wires at their sources, one to the battery, one to the column and a body ground. I'm not sure if it's the Instrument Panel you're referring to, but there was nothing hooked into it. I may sound a bit stunned, but could you be a little more specific on this I/P please...

The I/P panel is the interior fuse panel, right lower side of center console.

You need to elaborate a bit more on exactly what goes dead. Everything or just most of it. The problem can be just the battery cables or further down the electrical chain.

When the car dies will it crank and restart immediately? Do all of the warning lights on the dash die when it dies? The oil pressure light should come on when the engine dies as that is powered almost directly from the battery. The next time it happens, look at the oil pressure light before turning the key off.

In the mean time an inspection of the battery cable is a good investment of your time.

[ruley73]

Make sure your battery terminals are tight. Loose terminals alone can cause a lot of weird problems that seem unrelated.

A bad upstream O2 sensor may be to blame for the P0138 code. The upstream sensor may be sending the PCM an inaccurate lean signal that varies just enough to not trigger another code. The PCM thinks the engine is running lean (and also thinks the upstream sensor is working properly), so it feeds the engine more fuel to compensate. Since the upstream sensor never sends a rich signal to the PCM, the engine basically runs as rich as it can . This would explain the high voltage produced by the downstream sensor. It should be noted that the signal from the downstream O2 sensor is NOT used to help the PCM correct the fuel/air mixture like the upstream sensor. It is only used to determine if the catalytic converter is functioning at an acceptable level.

Definitely change the ECTS if it happens to be the old resin tip design. Your 2001 might have the newer brass design already installed though.

Another possiblilty is that the PCM might be fried. It sounds like you drove the car for a while with the broken O2 sensor. If the signal lead shorted to either the heater circuit's +12v supply or one of the ground leads that would certainly cause the P0138 code. If that happened for a long period of time it may have damaged the PCM.

[aafxsniper]

Ok just to clarify. When the car dies, it's as if I turned the key off. Everything goes dead. I don't turn the key back, I just put it in neutral and restart it. When it starts it's as if I'd had the battery out, I mean, the stereo is reset. No stations, time, etc. The engine code stays so it isn't a main power fault.
Here are the things I've done to date:
Replaced both battery cables...
New battery...
Plugs and wires...
O2 sensors...
Ignition module and coils...

This problem had been gone for a couple months, and then just re-appeared. Nothing had been done to cause it. I've checked all wiring under hood, altenator, starter, even all grounds and connectors...I've started the car and been underneath trying to get it to cut out by pushing and pulling wires and connectors..Nothing ever happens.. It's a mystery. I checked the interior fuse panel this afternoon and took the stereo out to check wiring around it.(just in case it was something stupid like a grounding power wire or something)
I just can't figure it out. I was hoping someone had had a similar problem..

[OldNuc]

Originally Posted by aafxsniper

Ok just to clarify. When the car dies, it's as if I turned the key off. Everything goes dead. I don't turn the key back, I just put it in neutral and restart it. When it starts it's as if I'd had the battery out, I mean, the stereo is reset. No stations, time, etc. The engine code stays so it isn't a main power fault.
Here are the things I've done to date:
Replaced both battery cables...
New battery...
Plugs and wires...
O2 sensors...
Ignition module and coils...

This problem had been gone for a couple months, and then just re-appeared. Nothing had been done to cause it. I've checked all wiring under hood, altenator, starter, even all grounds and connectors...I've started the car and been underneath trying to get it to cut out by pushing and pulling wires and connectors..Nothing ever happens.. It's a mystery. I checked the interior fuse panel this afternoon and took the stereo out to check wiring around it.(just in case it was something stupid like a grounding power wire or something)
I just can't figure it out. I was hoping someone had had a similar problem..

Exactly what engine code are you referring to, A SES light? When the car dies do all of the instrument panel warning lights go out or do any of them come on?

[fdryer]

Originally Posted by aafxsniper

Ok just to clarify. When the car dies..Everything goes dead... the stereo is reset. No stations, time, etc. . to date:
Replaced both battery cables...
New battery...

Its very clear and yet at the same time puzzling with repeatable symptoms - the radio memory and engine dying at the same time. A major power interrupt.

[OldNuc]

The Gen 3 has a different electrical distribution system than the Gen 2 but a defective ignition switch is not out of the question.

[ruley73]

I suspect a bad alternator. Go to Advance Auto, AutoZone, etc. and get it load tested. Make sure they get the ammeter probe around all of your grounds coming from the battery.

I also wonder if maybe your new battery has an internally failing positive terminal. Your chance of this is much higher if your battery is made by Exide. The terminal basically breaks off internally, but appears to be in good working order from the outside and the cable will still tighten down. Sometimes acid leaks out, but not always. Similar to the infamous AC Delco battery terminal failure in which the positive terminal just pretty much breaks clean off.

[OldNuc]

If I read his post correctly teh SES is not resetting, ther is a persistent P0138 code. If it is a battery problem the code will reset. The Gen 3 also monitors voltage and will set a code for that.

What I can not find identified on my drawing is the power source for teh BODY fuse in the I/P panel.

May not have to find it though.

To, aafxsniper. How did you test the Dome light function?

[OldNuc]

I do not think its the ignition switch......

[Leafy]

hmm gas in the oil we lend me to believe that the car is running obnoxiously rich (like 9:1 rich) I'm guessing that the front O2 sensor is funked but the computer thinks its still good. and the random shut down its just weird, hmm, is the computer on a different circuit than the ignition and injectors?

[aafxsniper]

Ummm, test the dome light??? It works..that's all I know.. Let me try to address some of these things.. First the battery, it is the second one cause an earlier post suggested the battery so I replaced my new one with a new one..weird, anyway, the altenator has been tested and comes up perfect... when the car dies the dash lights all stay lit. Let me try to clarify, when you first begin to start your car you get your lights come on. That's what it looks like when the car dies. The only thing I've noticed is the radio resetting. I am obviously losing power but not at the battery to computer side otherwise the ses light would be off. As I said, this happened a couple months ago and I thought it was solved.