P0137 Code

[Lanos01]

Greetings, all. I'm new to this board and this is my first question. Many thanks to Trey05woo for his excellent help in checking and cleaning the EGR valve on my '01 Lanos with 174k mi on the clock and was showing a P1404 code. (I'd give him rep if this board had it -Thanks, Trey.) Following his procedures I was able to determine that the circuitry was OK and gave the valve a thorough cleaning. While the valve was soaking in TB cleaner, I replaced the spark plugs and cables. The plugs that came out looked OK; white-ish tan with no erosion of the electrodes. I also sprayed TB cleaner into the throttle body and propped the throttle plate open so the cleaner could run out and evaporate. The inside wall of the TB was coated with residue from the crankcase gases. Idle was a bit rough when I first started the engine, but smoothed out after a few minutes. I figured some of the cleaner had found its way into the intake system. The CEL came on after I had driven about 12 mi. I read the codes when I got back home and it showed P0137 twice - one freeze frame and one pending (P1404 was gone). I cleared the codes and left the car parked for the night. That was yesterday. This morning, about 17 mi into my 45 mi drive to work, CEL came on again with the same codes as the previous evening.



Any ideas greatly appreciated.

[Trey05Woo]

Hey there glad to be of service. 0137 is a rear 02 low voltage code. Low voltage is essentially lean condition detected. While it's a possibilty that the cleaner you used contaminated the sensor, due to the fault location (rear after catalyst) I would not think it likely. Did the EGR code return? Because if it did, then that is your most likely problem: EGR flow in the engine is affecting 02 sensor performance. If not you can very well have a lazy sensor, or a clogged catalyst. Both are very probable at 174k miles. I have also seen many many rear o2 lean codes due to a weak fuel pump.

What were the freezeframe MV reading for the rear o2 sensor?
Compare them to the front sensor, this will tell you if there really is a lack of fuel condition present.
On a healthy running engine the front should fluctuate between 600-900mv and the rear should be a more steady 500-700mv
If the front reads normal and the rear reads 400 or lower the sensor could be lazy, or the catalyst can be clogged now allowing exhaust flow, therefore nothing for the sensor to read
if both read low, the engine is running lean
Using a scan tool and some propane you can instantly gauge the condition of the sensor as it will react instantanously to the propane in the exhaust mv will jump to 800, 1000 and above when you spray.
Keep in mind the rear will always read less than the front due to the catalyst
There should be 12v present at the sensor connector with ignition on, and a good ground.
You can also check your values directly at the pcm connector for both sensors under the seat. This will check the entire circuit.
You still want to chk the sensor connector for 12v and ground however

[Lanos01]

Thanks for the response, Trey. I've been out of town for the last week and not able to get on the forum.

The 1404 code still has not returned and although the CEL went out on its own, the P0137 code still shows on my code reader as 'pending.'
Driving at a steady speed at small throttle opening (60-65mph in 5th gear), the engine has a stumble/surge - almost lurching - until the car has been driven aprox 15-18 miles and reaches full operating temp, then smooths out. Could this trigger the 0137 code?

It'll be a few days before I have the time, but I will make the checks you suggest. Would starter fluid work in lieu of propane?
I'll post my results here when I get the numbers. Thanks again for your help. (I need all the help I can get!!)

[Lanos01]

Update: Still have not had time to get the readings on the sensors as Trey suggested, but the CEL came back on with more codes - five total. 1) P0172, 2) P0137, 3) P0405, 4) P0172, 5) P0405. Since some of the codes indicate lean and others are saying rich, I'm guessing not all of these sensors are bad.

What the car is doing now is surging/bucking at small throttle openings; 40-45 mph in 4th gear and 60-65 mph in 5th. If I take my foot completely off the gas peddle or push it to 1/2 or more, the engine smooths out and all stumble goes away. Running at 70mph or higher it stays smooth. Idle is also without any stumble.

Vacuum leaks? Bad EGR? Could it still be the O2 sensors?

Any thoughts appreciated.

[Puddle31]

I'm not a mechanic but always look for the easiest fix first..... did you change the fuel filter? have the fuel pressure checked? I was having similar problems and went through all the electrical stuff first (plugs, wires, etc) and it turned out to be fuel. I did the filter and it got better as i got good gas and ran a few tanks. If it was real bad it may take a few filters? just an idea.

[Trey05Woo]

3 codes there actually as they are repeated. the most important to note is p0405 which is egr pintle position low voltage. this translates to position. replace the egr valve, it is malfunctioning and driving the 02 sensors out of whack.

[Lanos01]

I'm not a mechanic but always look for the easiest fix first..... did you change the fuel filter? have the fuel pressure checked? I was having similar problems and went through all the electrical stuff first (plugs, wires, etc) and it turned out to be fuel. I did the filter and it got better as i got good gas and ran a few tanks. If it was real bad it may take a few filters? just an idea.

Thanks for the idea, Puddle. The fuel filter was replaced about two months ago. The main symptom was stumble at part-throttle operation; 30-40mph in 4th gear and 50-60mph in 5th. Pressing the peddle past about 1/2 took the stumble and jerkiness out, so fuel delivery was not an issue.

Thanks for your input. See next post.

[Lanos01]

3 codes there actually as they are repeated. the most important to note is p0405 which is egr pintle position low voltage. this translates to position. replace the egr valve, it is malfunctioning and driving the 02 sensors out of whack.

Thanks, Trey. Replacing the EGR did the trick. I had planned on testing the O2 sensors as you had suggested, but with my crazy work schedule recently, that hasn't happened yet. I was ready to just replace both sensors when I read your last post. I'll wait on doing anything with the sensors until I can put a few miles on the new EGR valve.

Rep to you, sir. Oh, wait... this board doesn't have rep Thanks a bunch!!

[Trey05Woo]

Good to hear, the EGR system on these cars is overkill. Its the same system designed for GM big liter engines. Any malfunction will cause massive side effects to engine performance. Thats what happens when cost savings come into effect and a 1.6l is passed down emisson components from 2.xl v6 and up engines lol.