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P0147, so I guess I'm yanking my O2, a few questions.


CanukGMC
10-17-2007, 09:53 AM
I haven't yanked an O2 on one of these newer trucks (new to me lol) and had a few questions.

1998 GMC Jimmy 4x4 4.3l

I'm pulling P0147 which should be the O2 post catalytic, basically the last guy in line right? How hard is it to get at? I've heard of these being seized in there, is there a good chance I'll snap it off in the pipe? That's my biggest fear right now, I don't want to go out there, put the gears to it and BANG half the O2 is still in the pipe and now I can't drive the truck. Is the wiring hard to trace to unplug? Any tips would be awesome, thanks.

old_master
10-17-2007, 04:06 PM
P0147 indicates a problem in the heater circuit of the aft catalyst O2 sensor. Piece of cake to change, don't even have to jack the vehicle up! Best to check it first though. With the key off, disconnect the sensor and check the resistance from the ground terminal to chassis ground in the vehicle harness, must be less than 5 ohms. Turn the key to the run position but don't start the engine. Check voltage on the heater terminal, should be battery voltage. If both check ok, most likely the sensor is faulty. Turn the key off and reconnect the sensor. Start the engine and allow it to achieve operating temperature. Shut it off and remove the sensor, the added heat helps when removing it. Put a dab of anti seize on the new sensors threads and reinstall. Entire process takes about 30 minutes. Better do it now, beats doing it in a snow bank!

CanukGMC
10-17-2007, 05:38 PM
P0147 indicates a problem in the heater circuit of the aft catalyst O2 sensor. Piece of cake to change, don't even have to jack the vehicle up! Best to check it first though. With the key off, disconnect the sensor and check the resistance from the ground terminal to chassis ground in the vehicle harness, must be less than 5 ohms. Turn the key to the run position but don't start the engine. Check voltage on the heater terminal, should be battery voltage. If both check ok, most likely the sensor is faulty. Turn the key off and reconnect the sensor. Start the engine and allow it to achieve operating temperature. Shut it off and remove the sensor, the added heat helps when removing it. Put a dab of anti seize on the new sensors threads and reinstall. Entire process takes about 30 minutes. Better do it now, beats doing it in a snow bank!

Thanks for the reply, this is the fourth time this code has popped in about 6 months. I erased the code(s) previously just to see if the code was popped prematurely, since this is the 4th time I think it's time to take it seriously, not to mention my horrid gas mileage. Good tip on the op temp before removing it, I'm just scared to snap it off and be up the creek lol. I'll give it a shot tomorrow maybe. Thanks!

old_master
10-17-2007, 08:14 PM
I've never had a problem removing O2 sensors. Use the special O2 socket or, cut the plug off and use a box end wrench and rap on it with a hammer to break it loose. You can use an open end wrench to tighten the new one. The aft sensor, (bank 1 sensor 3) will not affect fuel mileage. Its sole purpose is to monitor the performance of the catalyst. It has absolutely nothing to do with fuel trim.

If this thing has only acted up 4 times in the last 6 months, it would be next to impossible find something that erratic, I think I'd just replace the sensor and try it.

CanukGMC
10-17-2007, 08:40 PM
I've never had a problem removing O2 sensors. Use the special O2 socket or, cut the plug off and use a box end wrench and rap on it with a hammer to break it loose. You can use an open end wrench to tighten the new one. The aft sensor, (bank 1 sensor 3) will not affect fuel mileage. Its sole purpose is to monitor the performance of the catalyst. It has absolutely nothing to do with fuel trim.

If this thing has only acted up 4 times in the last 6 months, it would be next to impossible find something that erratic, I think I'd just replace the sensor and try it.

My sentiments exactly, thanks for the reply I'll tear into it on friday, hopefully the price isn't too steep on the parts lol.

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