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Explorer 5.0 Trouble Codes

Cooter_76

Sr. Member
Joined
May 18, 2004
Messages
854
I have about 600 miles on my Explorer 5.0/4R70W install. The check engine light came on recently. Code reader came up with P1506 - Idle Air Control Overspeed Error. I did a visual check for vacuum leaks and decided to replace the IAC (assuming it was original.) Now I have a P1151 - Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Lean Bank 2.
Possible Causes:
- Faulty Upstream Oxygen Sensor Bank 2
- Fuel pressure high or low MAF sensor dirty/defective
- Vacuum leak on engine
- Leaking fuel injector or fuel pressure regulator
- Faulty Powertrain Control Module (PCM)

I installed new 02 sensors during the conversion. Wires and connectors leading from the 02 sensors seem to be in good shape. I do have a K&N style oiled air filter. Don't know if it's possible that oil from the filter has gunked-up the MAF. The only vacuum line that's original to the engine is the molded line that runs under the upper intake manifold.
Has anyone dealt with these specific codes? I suspect a vacuum leak somewhere, but I'm not sure how to diagnose. Start spraying throttle body cleaner around the intake while listening for increased RPM? Is there a better method? Any other suggestions?
 

76Broncofromhell

Bronco Totalitarian
Joined
Jul 30, 2001
Messages
4,217
Loc.
Reno, NV
Vacuum leak could be one culprit. Check that you are pulling PCV through the intake tube (not just a vent to the atmosphere).

Check if the heating element is out on a O2 sensor on the passenger side and that you have the correct O2 sensor. Sometimes things get misboxed. I had a hell of a time finding a rich condition based on improperly boxed 4 wire O2 sensors in place of the correct 3 wire.
 
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Cooter_76

Cooter_76

Sr. Member
Joined
May 18, 2004
Messages
854
Vacuum leak could be one culprit. Check that you are pulling PCV through the intake tube (not just a vent to the atmosphere).

Check if the heating element is out on a O2 sensor on the passenger side and that you have the correct O2 sensor. Sometimes things get misboxed. I had a hell of a time finding a rich condition based on improperly boxed 4 wire O2 sensors in place of the correct 3 wire.
Thanks for the reply. PCV is connected to the upper intake manifold. I'll try trouble-shooting the O2 sensor. Are you sure about the passenger side being bank 2?
 
OP
OP
Cooter_76

Cooter_76

Sr. Member
Joined
May 18, 2004
Messages
854
I spent last week downloading and learning how to use FORscan. Did some data logging, sent files to EFI Guy, etc. He suggested I swap the O2 sensors left-to-right to see what would happen. I think I found the problem:



Looks like the front driveshaft pushed the crossover pipe up into the O2/flange fitting, crushing the sensor inside the bung.

 

EPB72

Contributor
Sr. Member
Joined
Jul 13, 2019
Messages
627
Loc.
Pleasant Hill, CA
Thanks for the reply. PCV is connected to the upper intake manifold. I'll try trouble-shooting the O2 sensor. Are you sure about the passenger side being bank 2?
Bank 1 is passenger side bank 2 drivers side...dirty throttle body,contaminated MAF [but may also set lean or rich fuel trim faults ] can you see data ..also air leaks betweem Maf and throttle body...
 
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