1995, 850, GLT, PO133 code

[Rbaratt]

I'm looking for some feedback on the PO133 code that I can not get rid of on my 1995 GLT. Here is a short list of things that I have done to try and eliminate this recurring code:

1. R/R both front and rear original O2 Sensors (replaced with Bosch). At 138,000 miles I figured it might be good idea just to do both and get it over with.
2. New Magnaflow Cat. I discovered the cat and the pipe between the cat and the muffler were corroded enough to warrant replacement.
3. Used propane to search for vacuum leaks. None found.
4. Re-set ECU, disconnected battery for 30 minutes.

The vehicle runs as well as it has always run, but the code returns after being cleared. It takes approximately 40-50 miles of driving before the CEL light comes back on with the same code.

Things I have noticed with the Autel scan tool.
1. LTFT is 6 or 7 and STFT if I think was around -3 to +3
2. O2 sensor seems to be switching normally
3. Under light load (10-14% TPS) the fuel system will read CL, but under heavier loads the system will read CL-Fault and when decelerating (no load) conditions I see OL-Drive.
4. ECT is reading 205 to 215 F, not sure about this, as my S70 reads much lower

Things I am thinking of checking include:
1. MAF sensor, I may try to clean the sensor with some MAF spray
2. Clean the O2 sensor connections and maybe apply some dielectric grease in each pin socket
3. I may order an ECT since this is the original

The bad news is that my 96 850 turbo is doing the same thing. I am going to try to work out this issue on the 95 before I move on t the 96. Whatever the problem is, it keeps the vehicle from staying in Close Loop. Any advice would be greatly appreciated.

[mecheng]

I have the same code I thought the sensor would have fixed things. Maybe it's the wiring or connector

[erikv11]

Any progress on this?

Only comment I can offer is that as I understand it, LTFT should be much closer to 0. Is it still 6 or 7?

So the O2 sensor thinks the car is running lean and is dumping in more fuel; vacuum leak (I know you checked ...)? O2 wiring/connectors all good? What kind of mpg are you getting?

[1998v70xcbill]

I had this same code. 1998 v70xc 191K, replaced front o2 no change. Cleaned grounds and reset ECU, went away for 2 months. Then it came back slow after reset, then much faster. Had poor city mileage and then started to have starting problems. I had a extra crankcase vent with catch, and noticed gas in vent catch tank. Checked fuel rail pressure and eveything pointed to a leaking injector. Replaced injectors with rebuilt from ebay $127. When replaced injectors, I could see which one was leaking, because the injector port on manifold was clean, compared to others. Engine runs (idles) smoother, mileage better, and code is gone for now. Sure is nice to have it running right. I'm getting 22+ city, where before it was 17-18mpg. Never thought a leakly injector would throw a P0133.
Bill

[Rbaratt]

On the advice of another member I performed an additional hard reset to the ECU, only this time I tied the two battery cables together for the entire time (overnight). The code has not returned and I have driven several hundred miles since the reset. The vehicle will run in CL but only under light loads...still displays the CL-Fault when decelerating and also under heavier acceleration. Occasionally I will see Open Loop Drive with a long deceleration such as when I exit from the highway. I drove the car 25 miles today and the LTFT started out 4.7, then 3.9, 5.5, 6.3, 5.5, 4.7, 5.5, and ended up at 3.9. This vehicle does not have a trip computer so I will have to check the mpg at the next fill-up.

I moved on to my 96 Turbo that also was getting the same code. This vehicle would start out by exhibiting CL-Fault status and quickly move and stay in the Open Loop status. I cleaned the MAF sensor and replaced both the front and rear O2 sensors...and performed the hard reset to the ECU. The code has not returned and this vehicle now runs in CL but it is very similar to the 95 in that it exhibits the CL-Fault when decelerating and under heavier acceleration. Occasionally I will see OL-Drive when decelerating but that quickly changes to CL as soon as I lightly press the accelerator. This 96 turbo shows a LTFT of 0 with the STFT running about -3 to +3 but seems to spend more time in the negative range. Fuel mpg is about 20-22, (city).

From what I have read, certain parameters need to be met before the vehicle enters closed loop, and with my limited understanding of this, I think that functioning O2 sensors and coolant temperature are important factors. I have also read that Open loop is defaulted to when O2 sensors do not function or there is a fault that prevents the ECU from determining conditions for closed loop. I have read that other faults that can do this besides O2 sensor failure, are failures of: MAF, ECT, MAP, TPS, and fuel pressure sensors. All sensors appear to be functioning normally on both of my vehicles.

For comparison I checked my 2000 S70, and found that once it enters closed loop it displays CL under all load conditions.

At this point I am a bit perplexed as to how to proceed. I would like to understand more about the CL-Fault, Open Loop Drive and OL flags that appear on my scanner but for now I am going to double check that I do not have any vacuum leaks.

[erikv11]

Hey thanks for posting. I am working to adjust LTFT so this is helpful to me.

It's too bad the ECT on your S70 won't swap to the 850's, that might be informative in your case. FWIW my Autel scanner reports ECT temp values that hover between 89 and 94 C (192 to 201 F) once the car is warmed up. That's on a handful of turbo and NA cars, all 95-98.

[mecheng]

I had a code for the ECT, replaced the ECT and thermostat and code disappeared

It had no effect on the P0133 code

[Rbaratt]

Erikv11,
Thanks for the information on the ECT.
- I think that you are correct that I should be looking for something causing a lean condition. If the goal of the LTFT is to keep the STFT at 0% then my '95 may still have a vacuum leak that I missed.

- On the other hand I just drove my '96 which has a LTFT of 0% and the PO133 code just came back with the CEL. I am going to tie the battery cables together and let it sit over night for another hard re-set. I previously only tied them together for about 30 minutes when I changed the rear O2.

Bill,
Thanks for the information on the injectors, and I saw your older post as well. I found this information in another post and I am going to take a closer look this as well.

"TSB number 824 dealing with a pulsation damper to damp shock waves in the fuel injection system. It's job is to reduce the shock waves in the fuel rail when the injectors open and close. These can produce the incorrect fuel flow at certain engine speeds. It goes on to say that it can affect the heated oxygen sensors (HO2S), thus our P0133 code, which points to a slow response in the O2 sensor before the cat."

MechEng,
I see that you have replaced the ECT and T'stat but have you tried anything else to get rid of the PO133 code?

-Rick

[mecheng]

The code came with the car, I reset it and then did a full tune-up. The code then came back after a couple months of driving. I just reset it again to see if it comes back. In the meantime I have purchased a proper O2 sensor socket, the sensor would not budge with a wrench and it started to slip.


If it re-appears, I will definetly change the sensor, it is a good idea to.

[Rbaratt]

I used a hand held propane torch to heat the bung on the front sensor and it came off fairly easily. The sensor on the rear was so corroded that I had to have a muffler shop cut out the pipe and weld in a new pipe with a new bung.