O2 Sensor Question

[BroncoJoe19]

michi,

those codes sound more electrical than a problem with the sensor.

bko

now that your cel is out, what kind of mileage are you getting?

If you are still getting under 12 mpg, you should definitely consider changing out your cracked exhaust manifolds.

BTW... HardMaple... great job holding his hand through this!

 

[michibronc]

The code p0141 refers to the oxygen sensor 2 in bank 1. Is that the sensor before the cat on the passenger side of the truck?

 

[bko4x4er]

michi,those codes sound more electrical than a problem with the sensor.

bko

now that your cel is out, what kind of mileage are you getting?

If you are still getting under 12 mpg, you should definitely consider changing out your cracked exhaust manifolds.

BTW... HardMaple... great job holding his hand through this!

well gas last week here was like 4.05

now its aound 3.60

what a change!!!!

and i am getting around 7-8 mpg

after replacing all those parts. it might be the manifolds. i will replace them and install a cold air intake and see what it does.

 

[HardMaple]

bko4x4er, if the manifolds are that bad you can replace them now or the next time you hit a speed bump wrong. I think replacing them soon would be a solid idea.

Michibronc, I just finished chasing P0141 on my own '96. Its pretty simple, except actually reaching the wires on the sensor. Mine was a combination of a new sensor and a crack in the Y-pipe behind the manifolds. This O2 sensor is located between the convertors (or behind the second one in a California vehilce).

For P0141:

1) Visually inspect the circuit. Make sure the wire is not sitting on the exhaust and burnt through. Check fittings for loose pins or corrosion. Make sure you actually check these things, my tailgate motor problem was caused by a corroded connector and I just replace a wire in my IAC circuit today because of a hidden wire break.

2) Key off. Disconnect O2 Sensor wiring harness. Key on, engine off. Measure voltage between VPWR and Sig Ret at the harness. If its greater than 10.5V - move to step 3. If less than 10.5V - make sure battery voltage is greater than 10.5V. Then Key off. Disconnect battery. Disconnect PCM harness. Check resistance between Pin 71 and VPWR at the sensor harness, and between Pin 97 and VPWR at the sensor harness. If the resistance is greater than 4.0 ohms, check fuse and then repair circuit. If resistance is 4.0 ohms or less, move to step 3.

3) If voltage in step 2 is greater than 10.5V or resistance 4.0 ohms or less, Key off - O2 harness disconnected. Measure resistance between HTR GRD and VPWR on the sensor side of the harness. If resistance is between 3 and 30 ohms, go to step 4. If resistance is less than 3 ohms or greater than 30 ohms, replace O2 sensor.

4) Measure resistance between GRD at sensor harness and the sensor case. Measure resistance between GRD terminal at sensor harness and Signal Return terminal. Measure resistance between VPWR terminal and sensor housing. If any of these are below 10K ohms, replace the 02 sensor. If all 3 tests are 10K ohms or more, move to step 5.

5) Key off, PCM disconnected, sensor harness disconnected. Test resistance between Pin 95 at the PCM harness (sensor side of the harness) and the following: Pins 24, 76, 103, 91, and 97. If the resistance is less than 10K ohms, repair the shorted circuit. If all resistances are greater than 10K ohms, move to step 6.

6) Key off, sensor disconnected, PCM disconnected. Check resistance between Pin 95 and GRD pin at the sensor harness. If resistance is less than 4.0 ohms, repeat all tests and then replace PCM if tests confirm this. If resistance is greater than 4.0 ohms, repair the circuit.

((BTW, I take no responsibility for you replacing the PCM as I did not perform the tests myself.))

Reset the codes. If P1131 shows up again, we can tackle it.

 

[michibronc]

Hey Maple,

Thanks for the post - excellent directions. I can look into it further tomorrow.

I've driven the machine about 50 miles and about 5 or 6 run cycles since having the codes cleared last. The only code that remains is the p0141. I think the lean codes were fixed by cleaning the MAF and / or replacing the cracked oil filler cap and pcv valve.

I checked my exhaust and 02 sensor setup. I have two cats, but no sensor in betweeen them. I have one sensor on the pipe leaving each manifold and a third after the second (larger) cat. I've disconnected the plug on each upstream 02 sensor to inspect and the connections don't have the slightest corrosion on them. The wires look pristine leading to the sensor as well. The sensors are Bosch - not sure if they are oem or not. No cracks or leaks in the pipes that I can see. I'm still kind of foggy on which sensor is "bank one - sensor two".

I also can't find a fuse that the heated 02 sensors run through. Is there another fuse box aside from the one in the cab? I looked several times at the schematic on the cabin fuse box cover and saw nothing that looked like it belonged to the 02 sensors at all.

The auto parts store didn't have any clue which sensor it was, but something that meisk5 posted said that p0141 wasn't due to the downstream sensor (which I assume is the one after the cat). It must be one of the upstream sensors but the naming scheme isn't making sense to me. I'd have thought that "bank one - sensor two" meant some sort of a downstream sensor. Too much confusion! Thank God for lots of cold beer to keep me thinking hard.

EDIT: After rechecking, I found that meisk5's post said that a different code wasn't related to the downstream sensor.

bko4x4er, if the manifolds are that bad you can replace them now or the next time you hit a speed bump wrong. I think replacing them soon would be a solid idea.
Michibronc, I just finished chasing P0141 on my own '96. Its pretty simple, except actually reaching the wires on the sensor. Mine was a combination of a new sensor and a crack in the Y-pipe behind the manifolds. This O2 sensor is located between the convertors (or behind the second one in a California vehilce).

For P0141:

1) Visually inspect the circuit. Make sure the wire is not sitting on the exhaust and burnt through. Check fittings for loose pins or corrosion. Make sure you actually check these things, my tailgate motor problem was caused by a corroded connector and I just replace a wire in my IAC circuit today because of a hidden wire break.

2) Key off. Disconnect O2 Sensor wiring harness. Key on, engine off. Measure voltage between VPWR and Sig Ret at the harness. If its greater than 10.5V - move to step 3. If less than 10.5V - make sure battery voltage is greater than 10.5V. Then Key off. Disconnect battery. Disconnect PCM harness. Check resistance between Pin 71 and VPWR at the sensor harness, and between Pin 97 and VPWR at the sensor harness. If the resistance is greater than 4.0 ohms, check fuse and then repair circuit. If resistance is 4.0 ohms or less, move to step 3.

3) If voltage in step 2 is greater than 10.5V or resistance 4.0 ohms or less, Key off - O2 harness disconnected. Measure resistance between HTR GRD and VPWR on the sensor side of the harness. If resistance is between 3 and 30 ohms, go to step 4. If resistance is less than 3 ohms or greater than 30 ohms, replace O2 sensor.

4) Measure resistance between GRD at sensor harness and the sensor case. Measure resistance between GRD terminal at sensor harness and Signal Return terminal. Measure resistance between VPWR terminal and sensor housing. If any of these are below 10K ohms, replace the 02 sensor. If all 3 tests are 10K ohms or more, move to step 5.

5) Key off, PCM disconnected, sensor harness disconnected. Test resistance between Pin 95 at the PCM harness (sensor side of the harness) and the following: Pins 24, 76, 103, 91, and 97. If the resistance is less than 10K ohms, repair the shorted circuit. If all resistances are greater than 10K ohms, move to step 6.

6) Key off, sensor disconnected, PCM disconnected. Check resistance between Pin 95 and GRD pin at the sensor harness. If resistance is less than 4.0 ohms, repeat all tests and then replace PCM if tests confirm this. If resistance is greater than 4.0 ohms, repair the circuit.

((BTW, I take no responsibility for you replacing the PCM as I did not perform the tests myself.))

Reset the codes. If P1131 shows up again, we can tackle it.

 

[BroncoJoe19]

Fords naming convention is that bank one is the same bank as where the number one cylinder is.

sensor one is before the cat sensor two is after the cat.

 

[HardMaple]

There is a fuse box under the hood, on top of the driver's side wheel well. It uses **** Fuses.

On a V8 engine, O2 #11 is near the engine on same side as #1 cylinder, #21 is near the engine on opposite side. On ALL single exhaust systems #12 is near the catalytic converters (behind them on California emissions, between them on all others), #22 does not exist. With dual exhaust #12 is around the cat on the #1 cylinder side, #22 is on the other side near the cat.

P0135 = HO2S HTR-11

P0141 = HO2S HTR-12

P0155 = HO2S HTR-21

P0161 = HO2S HTR-22

If you end up replacing the sensor, don't bother buying the Ford Factory socket. I used an open-end wrench (metric 20 or 22mm I think) because a socket wouldn't fit up there. The only real trick is trying to put the new one in because the wiring harness on the Bosch sensor is very long and when you are trying to thread the sensor back in, the wiring will try to spin it back out. But you may not have too much trouble since yours is in the rear position.

 

[michibronc]

Thanks, guys.

Does anyone know if I am correct in thinking that the #1 cylinder is on the passenger side of the engine on a '96 with the 351W?

 

[HardMaple]

Yes #1 cylinder is the front one the passenger side.

 

[miesk5]

Good Job Hard Maple!

Here is a diagram from the Heated Oxygen Sensor (HEGO), Catalyst, & Fuel Sys Monitor Related Diagnostic Trouble Codes TSB 01-9-7 by Ford for 96 4/10/03 that you can add to your files for future use here;;

http://v8sho.com/SHO/TSB0197HO2SServiceTips.htm#fig1

we have 3 O2 Sensors in our 96 5.0/5.8; One in each exh manifold and one before cat Location, 96 Bronco

Diagram shows the 4th for CALIF SMOG (Calif Emission freaked-out Broncos have 4 O2 sensors)

2 O2 Sensor Location Depiction; the 5.0 looks ok as a depiction, but whoever did the 5.8 one was prob on crack;

5.0

5.8

and the wiring overview diagram in same TSB

keep up da good work here!

 

[michibronc]

OK! Codes all gone!

I changed the downstream 02 sensor and that took care of p0141. The combination of changing fuel filter, cleaning MAF, changing cracked oil filler cap, PCV valve change took care of p1131 and p0174 codes.

Had one **** of a time getting out the downstream 02 sensor. I got it halfway out and it wouldn't budge. Heated it with propane blowtorch - still no budge. Had to take it to muffler man. Acetylene torch gets hotter. He still had to work on it for about a half hour of back and forth to get it out.

Took that opportunity to get a Flowmaster 40 installed too - sounds Niiiiice now.

miesk, maple, joe - thanks for all your posts and help. Much appreciated!

 

[miesk5]

Great stuff!

Glad to help!