smc704

Hi I just bought a 2004 lariat with the 5.4. They said they got it in with the CEL on and Im assuming they were getting DTC P2272, the same code I am currently getting. So they told me they replaced the bank 2 after cat sensor. I confirmed they did as the sensor does look brand new.

Driving the truck very shortly off the lot the CEL comes on. DTC P2272. I clear the code, it comes back on. So I check for vacuum leaks, all good. No exhaust leaks. Wire connections don't seem corroded. Truck runs great though.

My theories are:

-Maybe the after cat sensor is hardly switching the voltage at all due the oxygen gas content in the exhaust so the PCM recognizes the sensor as stuck lean?

-http://www.autoserviceprofessional.com/article/93003/advanced-air-fuel-and-oxygen-sensor-diagnosis

http://www.obd-codes.com/p2270

After reading these two articles perhaps I may have a similar situation where even though the sensor is meant for the specific vehicle it doesn't work. My sensor has a part number OZ A659-EE92. This I believe is a NTK sensor although an internet search of this p/n did not reveal this exact number but similar NTK numbers. Perhaps the NTK sensors aren't the proper length/number of holes. It seems like it is meant for my truck since the wire connection is clearly for this truck.

I am waiting for the dealer to get back to me to bring the truck in. I want to be able to explain to them what the potential problems and solutions are since they could not get it the first time. So has anyone had this problem before or have any ideas? Thanks.

lewissa81

It sounds like they put the wrong sensor in. It may fit, but that doesn't mean it's necessarily correct. I would advise them to use a Motorcraft 4L3A-9G444-AA. If the problem persists, then wiring would be suspect, in my opinion. The main function of the downstream sensor, in our trucks, is to keep an eye on the catalytic converter. The PCM compares readings from the upstream sensor with the downstream to determine the efficiency of the cat. It seems like if there was any other issue, besides a faulty sensor or circuit, then more/other codes would be thrown. Hopefully that made sense in my sleepy state.

smc704

Thanks, Im kinda leaning towards the same idea. Anyone else have any other thoughts? Or can weigh in on the NTK sensor not working for this application?

smc704

While Im here I was thinking about testing the wires going to the PCM with a multi meter. Does anyone know what colour each of the wires represent (i.e. the heating circuit, signal and ground wire)? Also how can I test these using the resistance function? Is there a minimal setting to have the multi meter set at so I don't damage the PCM?

smc704

Help! Anyone?

lewissa81

When testing the resistance(ohms) with a multimeter, a small charge is sent through the wire. Unplug the connectors to the pcm. Use a wiring diagram to find which pin on the pcm connector goes to which ever wire you're testing at the o2. Create a jumper wire to run the distance from either the pcm or o2 connector, to the multi meter connected to one of the leads. Set your multi meter to ohms. Touch one connector of the multimeter, to the end of the jumper wire to make sure you're reading zero ohms. Then connect the jumper wire and the other lead to each end of the wire you're testing. If you've never used a multimeter, then now is a good time to read the little book it comes with to get a fundamental understanding of what you're testing.
If you're testing for ground, or voltage, then put the black lead to an unpainted part of the frame somewhere, and the red lead to the wire coming out of the connector.
Hopefully that made sense. It's kinda hard to explain with out showing you in person. Maybe someone else can chime in and explain it better.

papa tiger

U really need to consider the replacement of Catz.

smc704

Ok Thats what I was thinking on how to do the test. Does anyone have a link to a wiring diagram for this model? Or can just explain what connector to unplug and what colour of wire represents the signal, heating circuit and ground?

As for the cat itself being bad...It could be possible. I don't understand on a high level how they work, I think the exhaust gas just passes through a unique metal that acts as a catalyst. I don't know what would go bad inside the cat though. And I don't think It would throw a STUCK lean code if it was the cat. Maybe just a lean code..I could be wrong

smc704

Update: I took the truck back to the shop and they put in the proper Motorcraft sensor p/n DY-992. I dont get the stuck lean code anymore but I now get P0158 O2 Sensor circuit high voltage bank 2 sensor 2. So the sensor is reading 1.5V or greater. WTF! Could it be the PCM? A vacuum leak I didn't catch? Please help!

lewissa81

Considering the dealer first put in a mystery sensor, I would check the wiring. It's possible they could have inadvertently created a short.
It is possible that this is the original code the dealer saw, and why they replaced that sensor to begin with.