O2 sensor code problems

[Jzer1720]

Hi, I'm new, and hope to get some advice from your experienced forum folks. My ladie's 2003 Ford Explorer Eddie Bauer 4.6L was throwing P0135, PP0053, and P0155, so I did the amateur thing and changed both upstream O2 sensors. I cleared the codes with my OBD2 scanner, and after a few cold/hot cycles of the engine, it throws the codes again right away after it starts up, I think the third time.
I've doublechecked and I put in the correct Bosch 15664 sensors from RockAuto. When I put them in, the connectors snapped in with ease. I believe they are all clean and straight. No wires are melted or touching anything hot.
Some online advice says it could also be a bad CHT, as this year does not have coolant temperature sensers. So, next, I changed the CHT also, although I had to fashion a special tool to reach in there without removing the intake manifold. What a pain! I also sprayed carb cleaner all over to see if there are any vacuum leaks. Didn't find any. It seems to run good, but the fuel economy is about 15.7mpg on the freeway -- I'm not sure if that is normal or not, but it sounds fine.
Still same codes. I can't imagine that both O2 sensors are bad from RockAuto? Any advice to fix those codes?
Here are the readings captured with the P0135 code:
Fuel Sys 1 CL
Fuel Sys 2 NA
Calc Load % 22.7
ECT 159.8
STFT B1 % 0.8
LTFT B1 % 0.0
STFT B2 % -0.8
LTFT B2 % -3.1
Engine RPM 946
Veh Speed 8mph
Spark Advance 32
IAT degF 59 deg
MAF (lb/min) 0.9
TPS % 18
O2S B1 S1 (V) 0.125
STFT B1 S1 (%) 0.8
O2S B1 S2 (V) 0.850
STFT B1 S2 (%) 99.2
O2S B2 S1 (V) 0.610
STFT B2 S1 (%) 1.6
O2S B2 S2 (V) .850
STFT B2 S2 (%) 99.2

The O2S readings of 0.125, and 0.610 are quite different. Everything else seems consistent, but I'm a complete amateur. Can you tell me if you can see any problems with these readings?

Someone said it could be a slight leak somewhere in the vacuum. I'm also wondering if this could be a poorly functioning fuel injector?

I really appreciate help you guys can give me. If i don't get this fixed soon I'm going to have to take it to the dealer. I hope it's not the PCM.
Thanks, Jim

 

[TechGuru]

 

[Jzer1720]

Thank You TECHGURU for all the great data and explanations of what the codes mean. Appears that I definitely have something wrong in the upstream O2 heater circuits for both banks. It just seems odd to me that they would both go bad at the same time, unless there is a commonality between them, but I see your 'possible causes' may cover this. I already replaced the actual upstream O2 sensors, and doublechecked the connectors for contamination or bent pins. So, I am left with shorts in harness, open/damaged circuit, or open ground. (the battery is new). I'm hoping PCM as last case.
As you know, it is very difficult to get up there to do any sort of troubleshooting through the connector. They give you about 2 finger's worth of space on one hand fully extended for Bank 1, and I have to balance a screwdriver on the connector to disengage it on the Bank 2 side. There must be a secret to squeezing in there, but to suffice for now, can you tell me the likely places I could look for damages in the wiring and also loose/open grounds? Would that be under the dash?

Appreciate all of your help,
Jim

 

[Jzer1720]

So far, in the past many hours and week, I have not found any damaged wiring or open grounds. No shorts. No water in connectors. New O2 sensors upstream. new, good battery. The car was kept well and is in great condition throughout. This is very strange to throw these codes now. I can't believe it's the PCM, as most posts say that is very rare and very last resort. Any other ideas of where I could look before going through the effort of a new PCM and having to have it flashed at the dealer? Thanks, Jim

 

[Jzer1720]

Well, it was burnt wires! But they weren't easy to find -- they were inside the heat sheathing above the EGR exhaust piping. As it turns out, that is the most likely location for this to happen. I wish someone could have told me without me spending many amateur hours looking for it. Anyhow, fixed without going to the dealer .

 

[Drewmcg]

Congrats. Good info.