2007 4.0L ODB Codes and part replacement

[Delphi Guru]

Hi All,
Great site...I'm glad I found it. I have read many posts before posting.....

I am getting the following codes from my ODB-II
P0135 O2 Sensor Heater Circuit Bank 1 Sensor 1
P0141 O2 Sensor Heater Circuit Bank 1 Sensor 2
P0155 O2 Sensor Heater Circuit Bank 2 Sensor 1
P0161 O2 Sensor Heater Circuit Bank 2 Sensor 2
P0403 Exhaust Gas Recirculation Control Circuit
P0443 Evaporative Emission System Purge Control Valve Circuit

I have replaced all of these parts and cleared the codes, but they keep coming back.
I also replaced the coil pack, all spark plugs and wires.
I have checked the PCV elbow hose and there are no leaks.
I sprayed carb cleaner all around the intake and hoses, no luck.
I also manually inspected all vacuum hoses and can not find any leaks.
I don't hear any hissing sounds.
The PCV seems good (makes noise when I shake it) but I will be replacing it as well as fuel filter and air filter tomorrow.

I've had 3 mechanics look at it and was told it's probably the wiring.
I went through wires on the wiring harness (bottom one on ECM) and did not find any cracks
or issues.
I was also told it could be the catalytic converter, fuel pump and/or fuel control module.

Sometimes I get the MAF code and sometimes I don't, but that has been replaced also.

BTW: It runs good, no idle issues, or hesitation when cold or at operating temp.
I was told there is a reason that I keep getting those codes and not to drive it until I identify why.

Is there a way to definitively identify what the problem is?

Any suggestions would be greatly appreciated.
Thank you!

 

[Todd Z]

Did you check the relays and fuses for the heater circuit for the O2 sensors?

 

[Delphi Guru]

Did you check the relays and fuses for the heater circuit for the O2 sensors?

I did check all the fuses, but not the relays. Thanks for that suggestion. Now I have to research how to test a relay...

 

[Todd Z]

Most of the relays are the same, Just swap it with another one in the fuse box...

 

[Delphi Guru]

I will do that. Thanks again...

 

[Delphi Guru]

I will do that. Thanks again...

I swapped all of the relays and it did not make a difference. Thanks for the advice. Also, just replaced the fuel filter, air filter and pcv....still get the same 6 codes....not right away though. I cleared the codes, then cranked it up and let it idle for about 10 minutes, no error lights, idles good, I go down the road and the wrench light comes on. After I come back, I check codes, there are none, I turn it off, crank it back up and the wrench light is now off, but the check engine light is on and the codes are back....

 

[Todd Z]

Unfortunately it sounds like its time for a diagnostic computer check…. It could be a broken wire, bent pin, corroded pin in a harness, failed insulation and wires are touching ( seen that many times behind the intake from the heat) or even a bad PCM....

I had to have Ford hook their scanners to mine as I was having an Evap code for the purge valve. Bad PCM, it didn't like the resistance it saw in the wiring and was throwing the code.... Replaced it ( 3 grand later) and its fixed...

 

[Delphi Guru]

Unfortunately it sounds like its time for a diagnostic computer check…. It could be a broken wire, bent pin, corroded pin in a harness, failed insulation and wires are touching ( seen that many times behind the intake from the heat) or even a bad PCM....
I had to have Ford hook their scanners to mine as I was having an Evap code for the purge valve. Bad PCM, it didn't like the resistance it saw in the wiring and was throwing the code.... Replaced it ( 3 grand later) and its fixed...

3 grand....Ouch! I think if I put 3 grand into my truck, I could probably sell it for 3 grand...lol.
I agree with potential wiring issue. I towed it to the Ford place a month ago. They reprogrammed the PCM (because the previous mechanic had swapped it out only to find it made no difference, then put my original back in without reprogramming it) and after Ford diagnosed it, they told me they did not get the codes I got, but got codes for right 3 cylinders misfiring, and that I needed plugs, wires, and coil pack, for the low, low price of $700. After thinking about it and reading bad reviews about their service dept, I declined and towed it back home. I purchased those parts for $155 and did it myself. I will try to test the wiring. Do you think the PCM could still be an issue?

 

[Mickey Luis]

My thoughts after reading this is a wiring problem. A lot of parts have been thrown at it including the PCM which is what most mechanics do first because it's easy and not their money. The first thing I would do is to get a wiring diagram for your vehicle to see what feeds the sensor heaters circuit. What should the voltage be at the heaters and where does the it come from in the wiring harness? Try to dissect the circuit and how it operates with simple logic such as what voltage should be at a connector or such as a relay pin.

Intermediate problems are tough to find but doable if taken in a logical approach. My two favorite YouTube wiring problems Guru's are "Scanner Dan" and "South Main Auto". They take this methodical approach of simple logic first and are very educational for those afraid of vehicle wiring. Often a visual inspection of the wiring harness will not reveal anything but it can be misleading without a diagram to see exactly the route of the wiring harness path along with the location of connectors that also must be closely examined for bad pins, corrosion, or a broken or shorted out wire. Getting codes for right 3 cylinders misfiring is very suspect of a wiring problem to me. I have a electrical background and was once a certified technician.

You apparently aren't afraid to do your own work, so please take some time to view the videos that are long but very informative and educational. I don't think your PCM is bad because they already tried replacement at the Ford Dealer with no change. It's common to blame things on the PCM first and try to updating it first, and then just change it if that doesn't work. I have a know it all friend who changed his PCM twice after one cylinder kept on getting a misfire code, but it kept on coming back shortly after replacing PCM. The real culprit was a bad wire not visible inside the wiring harness feeding the PCM on that one cylinder. A lot of time vehicle downtime (over a month) was lost plus money plus and frustration of shipping the PCM back and forth numerous times after arguing they had send him a bad one. He had the cash to throw parts so he took the easiest path he thought after listening to his mechanic friend.
Good luck!

 

[Delphi Guru]

My thoughts after reading this is a wiring problem.
Good luck!

Thank you for your advice and the video links. I will watch them and see if I can locate and fix a wiring issue.

 

[Delphi Guru]

Just wanted to let all know that IT WAS a wiring issue. The harness that runs under the battery and under/to the fuse box had 2 broken wires and over a dozen wires with insulation damage. After going through every wire in this harness and soldering/taping, ALL IS GOOD!
Thank you everyone for your advice!

 

[Mickey Luis]

Glad you found the problem! Nice job! Physically making the repair on the wiring harness is the easy part. It's the symmetrical logical approach that takes time but it's well worth your effort. Thanks for reporting the fix, many do not which is not helpful for this forum community education. Have a great Holiday!

 

[Todd Z]

yeah, the batteries leak, rot the harness..... Stupid design by ford.

 

[JC2008SportTrac]

Just wanted to let all know that IT WAS a wiring issue. The harness that runs under the battery and under/to the fuse box had 2 broken wires and over a dozen wires with insulation damage. After going through every wire in this harness and soldering/taping, ALL IS GOOD!
Thank you everyone for your advice!

It's ALWAYS a wiring issue, lol! Figuring out which wires went bad, and why, is the question.

Thanks for letting us know why those took a nose-dive. It can help others figure out why their's is doing the same crazy stuff yours did. Appreciate you coming back and filling us in on what you figured out!

JC

 

[Scotty86sw]

Thank you for posting a repair update. I am suffering the same issue and have repaired several wires with rotten insulators. But still having this issue. Gonna check where you found your issue and see if I can locate my bad wires. Ive been back and forth between buying a new harness or PCM for a few days and think I will try to investigate and repair first. And if still having issues I'll order a harness.

 

[Todd Z]

This is why I switched to AGM batteries.... No more leaking..