How many and where are the oxygen sensors on my 98 F-150 V6?

 

How many and where are the oxygen sensors on my 98 F-150 V6?

 

There are 4 sensors.
One in each head pipe up near the exhaust manifolds.
The other two are in about the middle of the rear cats on the top side at a bit of an angle.
They have two different lead lengths between the fronts and the rears and may be built a little different.
You need a special open sided socket to get them out with their cables attached.
they may be hard to break loose.
A torch to heat the lower body to a dull red color often helps them break lose quite easy.
Be carefull not to contaminate the new ones with lube on the tip that protrude into the pipes and cats.
For a look at the sensors and the total left and right cat assemblies, look at the Rock Auto site and at the info pictures.
Good luck.

 

Thanks for your reply. How do I get to the Rock Auto site? I clicked on the link in your post and it took me to a Dodge Ram place.

 

The 'auto' underlined, was added by this website as a way to sell board advertisement.
Just put Rock Auto into your browser and look at the list it returns.
Once you get there, click on the start button and indicate the make, year, model then what catagory your interested in for parts. Now by my telling you about this parts vendor, it's also a referral but I don't get paid for it. It's only a favor to you.
Good luck.

 

Speaking of O2 sensors, I am having some trouble with mine (I think). I am getting the following codes:

• P0141 - HO25HTR12 Heater Circuit Malfunction
• P0155 - HO25HTR21 Heater Circuit Malfunction
• P0161 - HO25HTR22 Heater Circuit Malfunction
• P1000 - Monitoring incomplete (occasionally)

A Ford Dealer said it was my O2 sensors going bad so I replaced all four for around $300 from AutoZone. Unfortunately, it keeps throwing the same codes. Can anyone recommend my next course of action?

 

Additional information:
I have a 2002 F-150 2WD with the 4.6 Windsor engine. The problem first occurred after pulling my RV to the Shenandoah Valley, VA, but not while pulling the trailer. It also occurs while towing. It has occurred at altitudes of 3500 feet down to sea level. When it throws the codes, the RPM's "hickup" and either steady out or stall the engine. I use an Edge Evolution CS to reprogram my truck for towing. The problem occurs whether it is set for towing or set to stock. It resets my overdrive switch and sometimes freezes my Edge computer. If I clear the codes, the truck will operate normally for a while until it happens again. This is how I made it back to Florida!

 

Well shame on the dealer. You are usually told these things by the service rep not the mechanic.
All the codes except the 1000 are for the same 'common' trouble.
Since all the sensors are in the same trouble, it's a harness or connector issue feeding both sides front and rear.
The cable splits near the front of the transmission to both sides and also has leads to the DTR shift position selector area.
It comes down the passenger side of the motor.
It could be open at the plugup.
Could be burned from hot exhaust, insulation damages by a pest etc and grounding out.
The codes are for detection of open circuit, grounds or cross to another circuit in the harness.
Additionally, a single fuse feeds all the OX sensor but I doubt it has blown because the fuse feeds the transmission and you would have servere shifting problems if it were blown
The 1000 code is not a specific trouble. It is just the result of the other codes not passing their monitor tests.
It will clear when all testing is complete and all test pass.
I would make a physical harness check for damage first then if not seen a voltmeter test to see an open or short on the sensor heater feeds.
Do not try to test the Sensors. You replaced them already and not the problem.
Get back with what you find.

Good luck.

 

Thank you! Your suggestion makes a lot of sense. I'll let you know what I find.

 

Well, the three sensors that threw the codes all hook into a common harness that runs up to the top rear (passenger side) of the engine compartment to a larger connector. The one that did not throw the code (sensor 1, bank 1) goes into another harness. Unfortunately, I cannot see enough of the harness to inspect it for damage. Most of it runs behind the engine and over the trans, and all of it is encased in plastic sleeve and electrical tape.
You mentioned using a voltmeter to check for a short or open circuit. How do I go about that? I have a multimeter, but which points do I put the leads to in order to test it?

 

I think you pretty much got the location of the trouble in the specific harness when you say the one sensor that is not in trouble is in a seperate harness.
This would lead me to believe that the sensors in trouble have open leads to the heaters in the sensors for the other 3. If just may be the plug/socket has corrosion and needs to be pulled apart and reseated.
To replace with the correct harness, get the tag number off the original harness so dealer can order the right one. No use waisting time further testing but just get the issue found for decision on repair.
If you can't fix it be prepared for cost of about $115 +/-. It should be just a un-plug remove /install deal.
For testing, cut one of your original sensor leads off near the sensor body and use it as a test lead plug.
You should see two whites a black and a grey.
Unplug the good one and test for 12 volts per the color code and do the same for one in trouble for compare.
Again, never try to measure the OX sensor element with an ohm meter. The meter in that function has a battery in the circuit that can damage the element. Only ID the heater circuit for color code if testing the heater element.
I have a new computer running on Windows 7 and is not compatable with my service disc unless I hook up my lap top to look at the color code info.
Good luck.

 

Well, I finally had an opportunity to pull the harness out so I can inspect. The first bad news is that Ford no longer makes the harness, so if needed I will have to use aftermarket or salvage. The second bad news is that I doubt the problem is in the harness. It turns out that only two of the three sensors tie into it. It thought the third one did, but it does not. There goes my common thread. I don't know how I will ever get that harness back in the way it was. Then, I still need to find where the problem actually is.

 

My truck stalled again on the way home this evening. I have heard that a leaking valve cover gasket could be leading to the O2 sensor faults and causing my truck to stall. Has anyone ever heard of this, and how can I check it?

 

Ox Sensor circuit failure is not considered the type of fault to disable an engine unless it blows the fuse that powers other functions. Even then it won't prevent the motor from starting and running but would affect 'drivability' to a large degree.
Loss of OX sensor operation causes the computer to sustitute fixed fuel tables so the engine will still run but get poor fuel mileage and run rich.
You have some other issue now.
Good luck.

 

Thanks for all the advice, Bluegrass 7. This is indeed turning out to be a tricky one, so I'll throw it out to anyone else who may have some suggestions.

It's the same issue I had all along. I just can't seem to track down the cause. The codes being thrown are still:

• P0141 - HO25HTR12 Heater Circuit Malfunction
• P0155 - HO25HTR21 Heater Circuit Malfunction
• P0161 - HO25HTR22 Heater Circuit Malfunction

It is not the sensors. It's not the wiring harness. Something is tripping these codes and triggering a response in the computer that is causing the engine to shut down. If I clear these codes, the engine starts again and runs normally until the next time. Is there any kind of vacuum or gasket leak that could be causing this? Could it have something to do with my Edge Evolution computer? Any suggestions would be helpful. Thanks.