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Oxygen Sensors - Where Are They?

oldtruckolderguy

By oldtruckolderguy
in Ask A GM Technician

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oldtruckolderguy New Member

oldtruckolderguy

Posted
Posted

My 2003 5.3L Silverado shows an error code that Bank 1 Sensor 1 heater circuit is bad. My electronic scanner shows that voltages from the sensors seem to be cycling OK but I want to replace the sensor with the bad heater so my check-engine light can be reset.

 

From other posts it appears that there are 4 O2 sensors but I can only find 2. Each of these is between the catalytic converter and the exhaust manifold. I unplugged the one I could reach easily on the drivers side and it has 2 black wires, a white wire, and a blue wire.

 

Where are the other two sensors? And most importantly exactly where is Bank 1 Sensor 1? I understand that Bank 1 is drivers side and Bank 2 is passenger side.

 

BTW, I know 2003 is not an old truck - but that is not my only one.

Thanks...

Wingnut Senior Enthusiast

Wingnut

Posted
Posted

There should be 4 on the exhaust. Front and rear O2's.

 

Shoot...I'm not sure about 03 pickups. So nevermind. That's what's on my GTO.

 

Your knock sensors are under the intake manifold in the lifter valley...That's what I had to replace on my '02. Code was 0342 (03 something anyway ;D )

Supertech64 Enthusiast

Supertech64

Posted
Posted

Bank 1 Sensor 1 is the one near the engine exhaust manifold on the drivers side, has a 4 wire connector that unhooks on the side of the tranny(I actually think the connector is along the fuel lines on a bracket against the tranny). Sensor 2 is right after the converter down(to the back) the pipe, and bank 2 is the other side in about the same places.

Wingnut Senior Enthusiast

Wingnut

Posted
Posted
Bank 1 Sensor 1 is the one near the engine exhaust manifold on the drivers side, has a 4 wire connector that unhooks on the side of the tranny(I actually think the connector is along the fuel lines on a bracket against the tranny). Sensor 2 is right after the converter down(to the back) the pipe, and bank 2 is the other side in about the same places.

 

Yeah, that's what I was thinking. 4 on the exhaust (same as the Goat).

oldtruckolderguy New Member

oldtruckolderguy

Posted
  • Author
Posted

Yes, you are correct. I looked in more detail and found the back two sensors behind the catalytic converters just like you said. The wires were hidden from my view when looking from underneath the engine. I had to move back directly under the converters and then saw the oxygen sensors and wiring.

 

I will replace the front left sensor, using a borrowed tool from the parts store, and see if my Bank 1 Sensor 1 error code can be cleared.

 

Thanks again Wingnut and SuperTech64 for being here for me.

Wingnut Senior Enthusiast

Wingnut

Posted
Posted

Good luck getting them off without them stripping.

 

If you've got the time, it's a really, REALLY good idea to shoot them with some penetrating stuff/anti-seize compound every couple of hours for a day before wrenching on them. My experience is that one out of 4 was put on cross-threaded and will come out like a mangled mess after you wrestle with it for an hour.

 

Of course...Since you're replacing them, you don't really care about it too much. I'm usually concerned with them stripping because we're installing headers and re-using the O2's....They're like $110 each for the GTO.

 

Good luck! :rollin:

MarkD Senior Enthusiast

MarkD

Posted
Posted

+1 on the penetrating oil...it will change the whole experience.

 

Also, if you have a tap/die set, it wouldn't be a bad idea to chase the threads.

Supertech64 Enthusiast

Supertech64

Posted
Posted
Good luck getting them off without them stripping.

 

If you've got the time, it's a really, REALLY good idea to shoot them with some penetrating stuff/anti-seize compound every couple of hours for a day before wrenching on them. My experience is that one out of 4 was put on cross-threaded and will come out like a mangled mess after you wrestle with it for an hour.

 

Of course...Since you're replacing them, you don't really care about it too much. I'm usually concerned with them stripping because we're installing headers and re-using the O2's....They're like $110 each for the GTO.

 

Good luck! :confused:

Taken out atleast a hundred(not that they go bad, but converters do and you have to transfer them over) in this type of truck and never stripped one myself... Penetrating oil is always a good idea though.

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