P0155 Will not go away after replacing o2 Sensor (Gen 1 Raptor)

[raptor305]

I have a 2011 Gen 1 Raptor 6.2. Pretty much stock except for the Roush Exhaust and Roush intake.

I got a CEL for P0155. (o2 sensor Bank 2 sensor 1)

I replaced the sensor and reset the light. It came back immediately. I exchanged the sensor at Advanced auto parts and the problem is still there.

I checked all fuses, looks for frayed wiring and nothing.

The only think i noticed is that the PCM is reading from the default fuel map and not using the o2 sensors at all for determining fuel trim. (not sure if that’s what it’s doing on purpose since the code is there)

Has anyone had this problem?

 

[FordTechOne]

P0155 indicates an issue with the O2 sensor heater circuit. It does not automatically mean the O2 sensor is bad, it needs to be diagnosed. When O2 sensor DTCs are set, the PCM defaults to open loop.

Since you’ve already replaced the sensor twice, it’s obviously not a sensor issue. Unless you used an off brand or a universal one that you wire in yourself.

That leaves you with circuitry and PCM. You may want to bring it to a mechanic to pinpoint the root cause of the issue.

 

[raptor305]

that’s the frustrating part. i’ve taken it to two local mechanics and both can’t figure it out. i have an appointment for the dealer but it’s over a month away and they said they would need the truck for a week which kills me

 

[MTF]

The wires going to the O2 sensors are tiny and become brittle from heat after many years.
Unfortunately, the dealer is the best bet to get it fixed, they have the laptop, program and procedures to properly diagnose it.

In the meantime, you can pull all three PCM connections and look for corrosion.
And look for damaged and/or burnt harness wires coming from the O2s to the PCM.

Can't hurt

 

[raptor305]

pcm connectors look good. no corrosion or water/dust infiltration at all. i checked the harness but i could see and damage.

i saw somewhere for the super duty they had a similar issue but the harness was getting damaged/shaffed on the passenger side a/c hose/tubing. but not on mine. fml

 

[TomDirt]

If I was waiting for a service appointment but still driving it I'd check the factory welds on the b u n g for cracks and put a temperature gun on both sides of both exhaust tubes and record any large difference in temperature once its warmed up; the dealer is going to charge you to do both checks anyway. When I was poor(er) we would swap the sensors and recheck that way. My '95 & '96 Broncos had O2 sensor problems too.

 

[Pedro Nevarez]

Did you figure out the cause of the P0155 code?