2008 Sierra P0054

[ken_man_1]

I've got an 08 Sierra, 4.3L Auto 2wd. The o2 sensor had a bad wire that corroded right at the sensor - no way of fixing it. So, I replaced with a Bosch "universal", and it lasted about 2 weeks. The next sensor that I bought was a Denso, and it only went 2 days before throwing a code. I had replaced it again, thinking that maybe something wierd was going on with these replacement sensors. Now, a new replacement came in, and I put it back in. Same code as the Denso - P0054. Does anyone have an idea of how to chase down this problem? I don't think it's the sensor again, so I need help, if anyone has a minute to post. Thanks!

[jaksdad66]

You may have an open circuit to the heater element on the O2 sensor. Check for a blown fuse or bad wire going to the sensor.

[ken_man_1]

I've checked the fuses, and I can't "see" a bad wire - I'm not sure what one is the power. I'll have to break out the dmm and start looking around.

[ken_man_1]

Originally Posted by ken_man_1

I've checked the fuses, and I can't "see" a bad wire - I'm not sure what one is the power. I'll have to break out the dmm and start looking around.

Upon further more detailed inspection, I've checked the power to the o2 sensor, and it's there - 12.1V on the pink wire. Without the sensor plugged in, I get 2.88V on the purple wire. Tan wire is 0v, and the grey/white wire there is no voltage. I checked the grey/white wire for ground, and it is not ground, either. From what I've found so far, that the grey wire is a ground. I've traced it all the way to the computer, and it is not grounded.

Does that give me a bad computer, or should I just ground the wire externally? HELP!!!

Thanks for looking! I appreciate anything anyone can offer.

[ken_man_1]

^^BUMP^^

Just looked at this truck again, still can't figure out what is going on. In October, it needs to go to emissions - they won't even look at it if the service engine light is on.

Does anyone have a schematic of the o2 sensor circuit?

I know it's been over a year, but problem not resolved.

[inafogg]

Originally Posted by ken_man_1

^^BUMP^^

Just looked at this truck again, still can't figure out what is going on. In October, it needs to go to emissions - they won't even look at it if the service engine light is on.

Does anyone have a schematic of the o2 sensor circuit?

I know it's been over a year, but problem not resolved.

a couple links that may help;
http://www.engine-light-help.com/P00...ine-light.html
http://www.engine-light-help.com/che...t-testing.html

[procaddytech]

Here is the schematic:

If you have power at the pink wire using a known good ground, but not with a test light from pink to gry/wht with the key on, the gry/wht wire is definitely the wire in question. Test for power across one of the other Ho2 sensor heater circuits to be sure the conditions are met for the heater to be commanded on, i.e. test across bank 2/sensor2 and look for a light. An O2 heater can be thought of like a light bulb that is turned on by the ECM to get the O2 ready quicker. (and the filaments burn out) Should be commanded on with key on, engine off, cold engine.

[ken_man_1]

That is exactly what I needed. I will follow up with this by week's end. Thanks a ton!!

[ken_man_1]

Originally Posted by ken_man_1

That is exactly what I needed. I will follow up with this by week's end. Thanks a ton!!

This weeks end turned into something different. I'll post when I get to it...

[Bob B]

Hi,
Maybe since all the sensors would come on at the same time, Then you could splice the grey/white wire from the closest other sensor?
If the computer has a blown circuit then this would bypass the problem and get you going.
Bob B

[ken_man_1]

Originally Posted by Bob B

Hi,
Maybe since all the sensors would come on at the same time, Then you could splice the grey/white wire from the closest other sensor?
If the computer has a blown circuit then this would bypass the problem and get you going.
Bob B

I would say no, because the computer must measure the resistance on each heater element circuit individually. That's how it knows what sensor is bad.

In any case, I tested the grey/white wire with engine cold (48 degrees F) and it never commands a ground to it. So I either have a bad wire or the computer is bad. It won't pass emissions with this going on...and due at the end of the month.

[ken_man_1]

Pulled the ecm, and checked the continuity of the wire to the ecm plug, it's good. Looks like an ecm failure. I'll be checking with the stealership on this one, and will post back with results asap. Thanks to everyone who posted!

[ken_man_1]

Dealership ECM $260, bone yard ECM, $75. Reprogramming fee, $129. Ouch - reprogramming fee...even on new dealership part.

[ken_man_1]

Okay, now after double checking EVERYTHING before going through with this ecm issue, I tested the o2 sensor wiring to the ecm, came back good. I also tested the resistance of the o2 sensor heater on the 02 sensors themselves. I found that the oem sensor reads about 6 ohms. The DENSO sensor reads 16.6ohms. So, now I go back to the parts store and read the Bosch sensor, and it reads at 5.5ohms. The Denso sensor is the 3rd sensor in there, so I was banking on it being good. I even ohmed it out before install, and it read just under 6 ohms. I'll not be buying a Denso o2 sensor again. Too much trouble. New Bosch sensor comes in on Friday, I'll post back and make the final report. However, I don't think the ECM is the issue anymore.

I can't stand intermittent electronic issues.