Freeze frame data

[FeetDry]

I'm looking at this freeze frame data, but I'm not sure how to read it.
DTC p0134 is Unsufficiant O2 sensor activity

[PCM Freeze Frame 2]
<0002>=0x0134
FUELSYS.FUELSYS1=OL-Fault
FUELSYS.FUELSYS2=OL-Fault
LOAD_PCT=23.9%
ECT=90°C
SHRTFT1=0.0%
LONGFT1=9.4%
SHRTFT2=0.0%
LONGFT2=9.4%
MAP=74kPa
RPM=2377rpm
VSS=120kmh
MAF=41.6g/s
TP=22.4%
<1235>=0x001F
<1236>=0x00C5
<1237>=0x03
<1238>=0x0A
<1239>=0x0A
<0002>=0x0134

All was running well at hiway speeds for about 5 hours, then it turned into a dog. Then, within 10-20 seconds, I got the SES light. It was running rich, (ran like crap). I figure the O2 activity caused it to go to OL mode. This is a stock tune. I don't have much tuning experiance, but I do know this stock tune is pretty crappy. (From a battery disconnect, it runs like crap until the LTFT's come inline.) I don't doubt the OL tables are what caused the rich (crappy) condition.
After shutting down and reading and clearing the Diag data, the problem went away.
I got the same rich (crappy) behavior about 5 hours into the return trip. I read and cleared the DTC's. This turned off the SES light, but it continued to run rich. I didn't pull-over to read it this time. I did it while driving. The problem didn't go away until I pulled over and shut down for a few minutes.

General Q's:
Do you always have to power down the PCM before the caused DTC behavior will go away? (Obviously clearing the DTC wasn't enough.)

What does 9.4% on the LTFT mean? 9.4% more than the closed-loop VE table, or the open-loop table? It say's it was running OL, but what table does the 9.4% apply to? Is it only the VE table that the % applies toward, or does the MAF have an effect as well?

Can anyone suggest why the narrow band O2 stopped switching, and after a pwr-down and restart, all is well again? I've never heard of an O2 going bad this way.

[DrkPhx]

You're exactly right about switching to OL. When triggered that code will cause the PCM to go into OL because there simply is not enough activity or feedback (indicated by a flat line on the scan tool) from that O2 in CL. The code will set when the voltage of the O2 is between .350-.550mv for 60 seconds or longer which is apt to happen in a steady state mode like hwy driving. Do you have a data log?


Do you always have to power down the PCM before the caused DTC behavior will go away? (Obviously clearing the DTC wasn't enough.)
- Disconnecting the battery will force the PCM to relearn some of the adaptive strategies like fuel trims and idle trims which will cause certain DTC's to come on later, rather than sooner. In you’re case you’re simply delaying the inevitable. :)


What does 9.4% on the LTFT mean? 9.4% more than the closed-loop VE table, or the open-loop table? It say's it was running OL, but what table does the 9.4% apply to? Is it only the VE table that the % applies toward, or does the MAF have an effect as well? - LTFT= Long Term Fuel Trim 1 for bank 1 driver side, 2 for bank 2 or passenger side. + trims indicates a lean condition, so the PCM is adding fuel by that much % to compensate. LTFT is a CL operation.


Can anyone suggest why the narrow band O2 stopped switching, and after a pwr-down and restart, all is well again? I've never heard of an O2 going bad this way.
- See above answer. It also sounds like a lazy or bad sensor with very little switching. The freeze frame data shows it happened at a steady cruise. You need to monitor the O2 with a scan tool. Expect to replace that sensor, but also check for exhaust leaks on that side to make sure.