Exhaust O2 Sensor Problem 04 Mach 1

theorangemach

New Member
Dec 21, 2020
8
0
1
30
Las Vegas
2004 Ford Mustang Mach 1
Bank 2 Sensor 1 Stuck Rich
Bank 2 Sensor 1 High Voltage


Symptoms: Misfire (but no code of misfire), Loss of power, hesitation in 3rd/4th gear
Past History: Misfire Cylinder 6 (Replaced Fuel Injector and all spark plugs and solved the problem)

Attempted Fixes:
- Replaced O2 Sensor for Bank 2 Sensor 1
- Cleaned MAF Sensor
- Fixed all possible exhaust leaks

My journey still continues as I try to get my car running normal again and I could use anybody's knowledge and help right now. Attempted Fixes stated above is what I've done so far to try and fix the problems that the car has been giving me. After each of these fixes I've pulled the battery and reset the computer and test drive it and the O2 Sensor code keeps coming back and the performance of the car hasn't gotten any better. As I was going to the muffler shop to ensure there are no exhaust leaks, They inspected my cats and said they were shot. I took it to my buddy's place to get his personal opinion as he knows more about my car than I do myself, he says that it may be the cat that's causing that O2 Sensor Code. I have a quarter size hole in the mesh inside the catalytic converter and didn't think it would cause the car to throw up the O2 Sensor code and have it running as it is currently. Is that true? I was thinking about just gutting the cat as my state doesn't do emission testing anyways, what do you guys think? Will it fix this O2 Sensor madness?
 
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Jul 11, 2020
13
1
13
59
Franklin, TN
I had three O2 codes for years. Both downstream sensors were bad, but changing them did not fix the problem. The problem was a broken wire and two stripped wires about a foot from where the wires from both sensors joined in the loom. Easy fix, but hard to find.
 

theorangemach

New Member
Dec 21, 2020
8
0
1
30
Las Vegas
I had three O2 codes for years. Both downstream sensors were bad, but changing them did not fix the problem. The problem was a broken wire and two stripped wires about a foot from where the wires from both sensors joined in the loom. Easy fix, but hard to find.
Thanks for the input. Haven't checked the harness for the O2 Sensors yet, but I don't see anything that could possibly have stripped or damage the harness since it's like way up there in the Chassis. I'll take a good look at it when I go under the car tomorrow and update as I go.
 

theorangemach

New Member
Dec 21, 2020
8
0
1
30
Las Vegas
Did you get your car fixed or have any updates. I have a couple of ideas if needed?
Haven't gotten it fixed. I've been saving some cheese before I take it to the shop just incase it needs a big fix. Shoot your ideas my way!

But an update: I gutted the cats and still having the O2 sensor code. I tried checking the O2 Harness but it's stuck above the transmission so I might have to pull the transmission and inspect the harness of the O2 Sensor. I have a OB2 scanner that gives me live feed and it's getting voltage and is reading stuff so it might not be the harness but I'm trying literally everything I can that I can come up with to tackle the code and so far nothing.
 

McFly2

Member
Nov 21, 2020
57
6
18
63
Cincinnati
OB2 scanner; live data: should give you voltage readings for your O2 sensors. Normal good voltage values should be between
.1 volt - .9 volt with engine running. If it has 0 volt; you have bad sensor or not getting voltage to the 02 sensor. On my 2001 Bullitt: O2 sensors 1 report to PCM to adjust fuel / air mixtures (STFT) and (LTFT). Sensor 2 will send a code; but not used to adjust fuel trims. Not sure if it works that way on your car?
Short Term Fuel Trims (STFT) should be between -5 / +5 % at idle and at 2500rpm. 14 % or more is going to be loss of power running issue [running lean causing PCM to add more fuel].
Since you have air fuel mixture out of whack (Bank 2 Sensor 1 Stuck Rich) you will have to disconnect your battery for hour or more; maybe to reset deep cell memory.

2004 Ford Mustang Mach 1
AN IDEA:
Bank 2 Sensor 1 Stuck Rich)
Bank 2 Sensor 1 High Voltage:
Could indicate an air leak (cracked manifold bank 2) or [most likely] your manifold to exhaust pipe connection is leaking on bank 2 side. That condition would alter the exhaust condition and be sensed by Bank 2 sensor 1. You will have to get it on the lift again; get your hand up to the pipe / manifold connection to feel for air leak. The bolts will be rusted and most likely be unable to be tightened. If the bolts are shoulder bolts; there will not be any threads to tighten any further any way.
It all still does not make sense. Because I would expect to see P0174 bank 2 lean under the condition I'm suggesting. All PCM's are not the same; sooo. That is why you might have to circle back to the fuel trims.
Im calling it a lean condition because your Bank 2 Sensor 1 Stuck Rich) is adding fuel trying to compensate for a lean condition.