George,

Thank you for excellent instructions. On a cold engine, I put a back probe pin into each green wire and connected incandescent light probe ground clip to one and the tip to the other. Light came on with key in on position.

No change to O2 data from pumping brakes or pinching booster vacuum line. I haven't noticed any drop in RPM when braking but will double-check.

Freeze frame data did not update. The light had gone off but the code remained. I can clear code and drive it tomorrow to get updated data. The log data from 8:28 is about when the light came on so combined Bank 1 ST/LT was ~3% and Bank 2 ~74%. Range is all over the place for both banks.

I previously had an unmetered air DTC (P0171/P0174) and did a smoke test. I had a big hole in dipstick tube and replacing it cleared code. There could be a smaller leak I missed.

Kevin

 

Back probing is a valuable technique but not here because you were significantly increasing the load on the heater circuit when it now has to drive the sensor heater and the incandescent light in parallel. That's why the instructions were to remove the connector and test at the harness wires so that the test light was the only load. If you got a bright light then the driver is working.

Before going any further you should complete the test suggested by swatlkk:

"As far as non-electrical sources for this behavior, have you tried capping off the vacuum lines that attach to the brake booster, HVAC/4wd system, & PCV hose and seeing if that has any affect on the idle speed? A drop in idle speed when capped off that is below that of the accessory being connected normally would indicate that it is possibly flowing air that may not be accounted for by the PCM."

The fuel trims you are getting would not likely be a small leak.


George

 

George,

Thank you for patience.

I capped off PCV valve and pinched brake booster and HVAC vacuum lines - RPM dropped and then recovered. Car idled very poorly entire time vacuum was isolated but RPM were steady at ~1500. ST fuel trim on bank 1 and bank 2 were both 51%. LT fuel trim was 0% on both banks. Once I removed PVC cap, reconnected hose, and removed pliers from vacuum lines the car almost stalled but then recovered and idled fine. ST fuel trim on bank 1 dropped to -13% and bank 2 -14%. LT remained 0% on both banks. System A was closed loop and System B was open loop.

With cold engine, I removed B2S1 sensor and put pins in green wire terminal connectors and connected probe and alligator clip. No light with key on put as soon as I started engine the light came on.

I took for a test drive and ~5 minutes System A went into open loop. After 15 minutes combined ST/LT fuel trims for bank 1 were 2.3% and bank 2 22.7%.

I never got CEL but there are pending codes for P0151 and a new code of P1153 (too few O2S R/L and L/R switches B2S1).

Thanks again. Kevin

 

Did you capture the O2 sensor graphs to see if bank 2 pegged low (lean condition) before the pinched off vacuum hoses, during or after release?

Which vacuum hose caused the rpm change when closed off?

So fuel trims were positive with the vacuum lines pinched off and negative with the vacuum line opened back up? What were the fuel trims before you touched the hoses?




George

 

Tried to re-create today but couldn't.

+30 sec: System A went closed loop
+ 4 min: Bank 1 ST 0% LT 2.3% & Bank 2 ST 0% and LT 22.7%
Blocked off HVAC, Booster, and PCV in that order
+ 5:30 min: Bank 1 ST -18% LT -4.7% and Bank 2 ST -29.7% and LT 13.3%
+ 20 min: DTC P0151 with pending P0102

There wasn't a large RPM drop for any of the vacuum lines being blocked but biggest was for PCV. Engine lowered a bit but recovered after ~30 seconds.

 

I see two different things happening here which may or may not be related. First, it looks like Kyle was right (and I learned something) and you have a significant vacuum leak that needs to be addressed. Using bank 2 as an example, before the test your ST trim is zero and your long term trim is 23%. That means the a stable condition exists where fuel has been getting added at a pretty high rate to offset a lean condition. The fact that your ST trims go negative when you clamp of the vacuum lines says that a confirmed vacuum leak was adding significant unmetered air (after the MAF sensor) and its source was one of those vacuum lines or downstream systems. This also affected bank 1 in a similar way just to a lesser extent. You can watch the trims and O2 graphs in live data in real time as you clamp of the hoses to figure out which one it is and then you need to repair that leak.

That leak is normally pretty stable but intermittently bank two goes so lean that the O2 sensors lose fuel control, the sensor pegs low and the fuel trims go sky high, and a code is set. This can be a real or improperly reported massive lean condition caused by a vacuum leak (possibly the same one getting worse) , restricted injector(s), PCM/sensor/injector wiring or control, power, grounds, etc

Since the P0151 fault may just be a variation on the known steady vacuum leak, that should be addressed first. You also have a pending MAF code so we will need to diagnose the MAF circuit as well.


George

 

Changed out PCV and tube.

From start to 10+ minutes LTFT for both banks are ~ -7% and STFT are both ~ 0%. No change if I crimp HVAC, Brake Booster, or PCV hose.

Once engine gets running bank2 starts creeping up until I get about +20-25% LT and +50-55% ST. B2S1 O2 sensor pegs at .8mv and doesn't move. B1S1 operates correctly.

I did a smoke test on intake and found a couple of small leaks which I was able to fix but a rather large leak coming from distributer.

I did a smoke test on exhaust through bank2 O2S port and found a small leak between exhaust manifold and pipe at connection. I also found a rather large leak where muffler and pipe connect - one of the bolts rusted clean off and now there is only one holding it together.

B2S1 sensor which is only 4-6 months old is totally black with carbon build up similar to spark plugs on bank 2 which are only ~1 year old.

Still have the P0151 but P0102 is no longer pending.

 

You need to fix those leaks, I think the exhaust leaks might be the key hers, the extra unmetered air is causing the sensor pegged lean and the rich condition.


George

 

Thanks. I'm on travel next two weeks but will get back at it as soon as I return. Best orders of repairs 1) distributer, 2) muffler union, 3) exhaust union? Or does it not matter....

 

I would fix those exhaust leaks first


George