Code 172
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Elder User
Joined: Jul 2011
Posts: 793
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From: Vernon, BC
Code 172
Hello all. I tested my truck today with a code reader and obtained code 172. My book says that's code HEGO (HO2S) Sensor fault/lean. I think that means my O2 sensor is sensing a lean condition. Is that correct?
I also think my O2 sensor is VERY old so I'm going to change it when I have the Catalytic Converter changed to a new one. I don't think either one has been changed since the truck was new.
Once I've changed the O2 sensor and the Cat I will test it again. I just want to confirm what the code means.
Thank you.
I also think my O2 sensor is VERY old so I'm going to change it when I have the Catalytic Converter changed to a new one. I don't think either one has been changed since the truck was new.
Once I've changed the O2 sensor and the Cat I will test it again. I just want to confirm what the code means.
Thank you.
Junior User
Joined: Jan 2010
Posts: 61
Likes: 0
From: Woburn, MA
I'm getting the same code on my '95 F150 w/5.0L automatic.
So far I've changed the O2 sensor THREE TIMES, (first time was a Denso, second time was a Bosch, then I went with the Motorcraft one.) The code STILL comes back. I've also changed (ALL NEW PARTS), egr, egr tube, plennum gasket, vacuum canister (coffee can), egr vacuum solenoid, carbon vapor canister, purge valve, cap - rotor - plugs - wires, fuel filter, pcv valve. ALL the plastic vacuum lines have been replaced with rubber ones.
I've taken it to the exhaust shop and had it checked for leaks and NONE were found.
Could it be a dirty MAF?
I'm loosing my mind!!
What are the voltage specs for the O2 so I can check for bad wire harness?
So far I've changed the O2 sensor THREE TIMES, (first time was a Denso, second time was a Bosch, then I went with the Motorcraft one.) The code STILL comes back. I've also changed (ALL NEW PARTS), egr, egr tube, plennum gasket, vacuum canister (coffee can), egr vacuum solenoid, carbon vapor canister, purge valve, cap - rotor - plugs - wires, fuel filter, pcv valve. ALL the plastic vacuum lines have been replaced with rubber ones.
I've taken it to the exhaust shop and had it checked for leaks and NONE were found.
Could it be a dirty MAF?
I'm loosing my mind!!
What are the voltage specs for the O2 so I can check for bad wire harness?
Junior User
Joined: Jan 2010
Posts: 61
Likes: 0
From: Woburn, MA
Forgot to mention, my truck runs great, no stumbling, no hesitation, no miss. Neither at start-up or when warm. Mt mpg isn't great put it's not terrible either.
When I restart the truck the check engine light goes off but comes back after a mile or two.
When I restart the truck the check engine light goes off but comes back after a mile or two.
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Elder User
Joined: Jul 2011
Posts: 793
Likes: 2
From: Vernon, BC
Drivingmad44, I don't know what the voltage specs are for the O2 sensor. However, in my research, I discovered that the wires to/from the O2 sensor have to be continuous. They cannot have any splices as that changes the resistance and thus the voltage being sent to the computer will be off. One can also have the O2 sensor wires routed too close to a heat source so the insulation gets damaged. I hope this information helps you.
My issue was traced to a split spark plug cap. I replaced it and my miss went away along with the codes.
My issue was traced to a split spark plug cap. I replaced it and my miss went away along with the codes.
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