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Baffled by O2 sensor codes on 98 Taurus SE 3.0L DOHC

I bought a 98 Taurus with a bad engine (timing chain problem). I replaced the engine with a 47K mile engine and all was well except for an SES and code P1132 (fuel mixture, bank 1, upstream O2 sensor). I checked for vacuum leaks, air inlet restrictions, exhaust leaks, and replaced the PCV valve. I reset the code and it came back after a few minutes of driving. I cleared it several more times and couldn't find anything else wrong, so finally I swapped the two upstream O2 sensors and reset the codes. This time I got a different code, P1152, which is the corresponding code but on bank 2 rather than bank 1. The bank 1 code did NOT return. After clearing the code several times and getting repeatable results, I thought I had isolated the problem and bought a replacement O2 sensor, a Bosch OEM type sensor p/n

13117, and installed it in place of the "bad" one. With that sensor, I soon got a P0155 code which indicates an HO2S heater circuit electrical problem. Thinking I had bought a bad sensor, I replaced it with another new one, cleared the code and got the same P0155 code back again. I cleared it a couple more times and it kept coming back. With the idea that maybe I damaged the wiring somehow I put the original sensor back in the car and cleared the code. (note: both Bosch sensors I removed were black with soot, unlike the light tan original sensor). Sure enough I now get the P1152 code back again, but no P0155. I was tempted to just go to Ford and buy an OEM sensor, thinking that would solve the problem, but Ford wants $144 for the sensor, which is a pretty expensive test if I am wrong. Bosch also has a Universal type sensor that is a little more expensive than their OEM type, but I can't be sure if that would be any better, and I don't want to just start throwing money at this problem.

Is there something else I am missing here? Any suggestions on how to proceed would be greatly appreciated.

Thanks in advance, Steve

Reply to
Steve Judy
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====================== It sure sounds like you diagnosed it correctly. Can you take the bosh back? Tell them it doesnt fit or whatever. Then get a sensor from another parts place. Only other thing I can think of is the lean code overides the heater code.....So you have both problems, with the old sensor in it just wont set the heater code cause the old sensor is bad.

Reply to
Scott M

I've taken one back already and they swapped it with another of the same type with the same symptoms, but now they are saying that the problem is in my car, not the sensor. I don't agree, but unfortunately I don't have enough strong evidence to prove it. I would think that a heater problem (electrical) would probably preclude a sensing problem if anything, but again, I am not sure how the diagnostics work, so it makes it difficult to prove a point.

Steve

Reply to
Steve Judy

WIth both sensors out, take a Ohm meter and ohm out both the old one and the new one matching the wires and pins . Are the readings in the ball park? Maybe the wiring on the new one is mislabeled or on the wrong pins.

I would think that a O2 heater sensor would check for current flow to the sensor. If it did not detect it, it would flag it as bad. That's why i suspect a wiring fault of some type.

Bob

Bob

Reply to
BOB URZ

====================== Oh yes, I think Bob is right. I remember buying O2's for Crown Vics and the wires on the round plug would be in the wrong places. I also remeber having to buy them from Ford and having to give them a "calibration code" off the door sticker to get the correct one.

Reply to
Scott M

Reply to
Thomas Moats

I can see where fuel pressure may have contributed to the original code (P1132) but I can't quite understand why the code would follow the sensor and definitely don't understand the connection (if there is one) between fuel pressure and the heater circuit. I'm thinking that must be a separate problem... I'm sure there are a lot of things that I don't understand, but I'm certainly willing to listen. I'll check fuel pressure tomorrow and post my results. Thanks for your help.

Steve

Reply to
Steve Judy

Reply to
Thomas Moats

Thanks for the detail! I had already changed the plugs, wires, PCV valve and air filter, but since the code moved with the sensor, I stopped there. I'll check the pressure tomorrow when I can get the car thawed out a little. Thanks for your help!

Reply to
Steve Judy

=========================== Did it have a running problem too. Seams if the fuel pressure is low you would have a drivability problem also. Like hesistation when its cold....

Reply to
Scott M

Reply to
Steve Judy

Reply to
Thomas Moats

I checked the fuel pressure this morning. With the engine cold it was about

32psi. As it warmed up, it dropped to 30psi. It seems to be regulating well (29psi-32psi) as I go from idle to 2-3k RPM and back to idle. The spec for this engine is 26-45psi. I'll check it later with the engine hot.
Reply to
Steve Judy

I think its time to read what Bob wrote again :)

WIth both sensors out, take a Ohm meter and ohm out both the old one and the new one matching the wires and pins . Are the readings in the ball park? Maybe the wiring on the new one is mislabeled or on the wrong pins.

I would think that a O2 heater sensor would check for current flow to the sensor. If it did not detect it, it would flag it as bad. That's why i suspect a wiring fault of some type.

Bob

Reply to
Scott M

I did that yesterday too. The only low-resistance path is on the 2 pins closest to the key on the connector. The OEM part measures 8.0 ohms while the Bosch replacement part measures 6.4 ohms. All other circuit combinations showed an open circuit.

Thanks, Steve

Reply to
Steve Judy

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