02 sensor problem (bank 2 sensor 1)
 

Hello everyone

I had the guy at AutoZone scan my car and this is what the printout said:

Fuel trim bank two condition
The ECM has detected a rich or lean air/fuel ratio condition on engine bank 2
If bank one and two are set together suspect a fuel pressure condition or MAF sensor fault

- Failed H02S21 (Heated 02 sensor - Bank 2 Sensor 1)
-Ignition misfire condition
-Engine mechanical condition

Definition: Lack of heated oxygen sensor - Bank 2 Sensor 1 H02S21 switch sensor indicates lean

Explanation: ECM tried to correct for a lean condition - ECM made rich correction but was unable to bring within specifications

Probable Cause: Failed H02S21 Bank 2 Sensor 1
Open or Short circuit condition
Failed fuel pump or blocked fuel filter
MAF sensor failure
Vacuum Leak



Anyway can anyone tell me if I am correct in assume all of these problems stem from the Bank 2 Sensor 1 02 sensor? And if so could you tell me if that is passenger side/driver side and upstream/downstream? I really appreciate any advice as I would like to handle this on my own.

2006 Ford Explorer XLS 6 cyl

Does the 06 v6 have dual exhaust? if its dual its on the drivers side, before the cat converter, which is your upstream

It has no bearing on whether the vehicle has single or dual exhaust. Each bank of cylinders has an O2, B2S1 is the 1st sensor after the exhaust manifold (pre CAT) on bank 2. In your case that would be the driver side. The designation of the O2 post CAT would be BxS2.

The S1 O2 are used by the PCM to adjust fuel/air ratio, the S2 are only to monitor the CAT efficiency..

Do not assume that you have an O2 issue, use a proper SCAN tool (computer) and read the live data, MAF, O2 and fuel trim. Philip

I agree with Aquanaut. This probably is not an oxygen sensor issue but rather a vacuum leak.

-Rod

Where is bank 2 sensor 1 on a 02 Ford Explorer xls

Welcome to the forum!

Did you read post number 3 above? I think Aquanaut did a pretty good job of explaining it. Do you have a more specific question?

-Rod

live data!! What am I looking for?
 

I have a 96 explorer awd v8. I'm pulling the same codes and I know enough to know that this is not the o2 sensors. I've got a proper scan tool to read live data but I have no idea what I'm looking for to narrow this down. I've collected a laundry list of possibilities from maf sensor, to vacuum leak, to manifold gasket. What am I looking for to narrow this down?

now that I write it, those are all pressure related and would probably read the same in live data anyway... Mother fu....

any help is greatly appreciated!

Welcome to the forum!

Out of curiosity, what codes are you pulling?

Are you familiar with what the expected O2 sensor voltages should look like for sensor 1 versus sensor 2? You're basically wanting to monitor the switching frequency of sensor 1 and when it reads lean versus rich relative to the readings of the short term fuel trim compared with the MAF flow readings.

-Rod

Codes... 8 of them...
 

All upstream o2 sensors here they are:

p0133 o2 circuit slow response (b1s1)
p0153 o2 circuit slow response (b2s1)
p0155 o2 heater circuit (b2s1)
p1151 lack of ho2s21 switches sensor indicates lean
p0133(repeat don't know why?) b1s1
p0153(again) b2s1
p0155(again) b2s1
p1151(again) ho2s21

the bank 1 sensor is brand new, I'm going to replace the bank 2 sensor now and run the truck around a bit (had to custom make a tool for the angle ended up easier than taking the console apart)... I'll report in the morning.

I want to jump to a computer fault, but after talking to my father and writing to you I'm starting to rethink my angle... It's got a minor exhaust leak I believe, but also a long hold to start (meaning I have to crank it for about 3 seconds). I had a v6 that fired much quicker than this. She runs like a dream when shes going..

The repeat of codes is probably due to one set being "active" and the other being "stored" or "historical", meaning it's been throwing these codes for awhile and the last time you drove the vehicle they were still active.

With the range of codes you list, I'd be focusing my efforts on looking for a vacuum leak and repairing that exhaust leak. The P0133 and P0153 could both either be caused by a vacuum leak or an exhaust leak.

The P0155 would most likely be due to either a bad bank 2 sensor 1 sensor, a wiring issue to the sensor (check the fuses), or possibly a PCM issue. I wouldn't jump to the PCM yet though.

The P1151 has several possible causes, but could again be due to a vacuum leak (among several other things - fuel pressure, oil dipstick not seated, PCV valve issue, plugged air filter, etc) and could also contribute to the P0155 code.

-Rod

Thank you!
 

I seem to want to always go worst case scenario, but I should listen to my dad more too. Thanks Rod, I appreciate the knowledge. I haven't owned fords long (truth be told I never would have bought it except it fell in my lap at too good of a price). I've got other makes funny little problems down I hope it won't take long to get this explorer down.

2013 expedition 5.4
I just got a check engine light on for bank 2 sensor 1 lean. no evidence of a vacuum leak by a visual inspection, no loose hose fittings etc..
Runs and idles absolutely perfect. I bet this gets fun! 80K on the clock, no rust or corrosion on truck. any thoughts?

Confirm the lack of vacuum leak, either with a smoke machine, or monitor the fuel trims along with the O2 DATA.
This code is triggered by many reasons from pirate air, low fuel pressure, bad fuel injector, poor burn in cylinder.

Well that was easy. Too easy?? we'll see. I cleaned the mass air flow sensor and tossed in a new air filter while I was there, took for a nice long drive so it could re learn fuel trims etc.. It runs like new and no light.

If you reset the codes with a scanner or battery disconnect, don't be surprised if the CEL comes back, as the ECU runs its monitor check..

If to light cleared by itself you are probably in the clear..

Good Luck..