firepop5

On a 2001 Impala with 3.4L, how many oxygen sensors are there and where are they located?

Mike Sigmond

You have 2.

One before the cat & one after the cat on your exaust pipes.

I cant find a picture but here is what the book says...



Removal & Installation

Upstream HO<SUB>2</SUB> S1

To Remove:


NOTE: If the engine temperature is lower than 120 °F (48 °C), the HO<SUB>2</SUB> S1 sensor may be difficult to remove. Excessive force could possibly damage the threads in the exhaust manifold.

1. If necessary remove the fuel injector cover.
2. Disconnect the HO<SUB>2</SUB> S1 sensor electrical connector.
3. Using an oxygen sensor removal tool carefully remove the heated oxygen sensor.

To Install:

1. Coat the threads of the oxygen sensor with anti-seize compound
2. Install the HO<SUB>2 </SUB>S1 sensor. Tighten the HO<SUB>2</SUB> S1 sensor to 30 ft lb (41 Nm).
3. Connect the HO<SUB>2</SUB> S1 sensor connector.
4. If removed, install the fuel injector cover.

Downstream HO<SUB>2</SUB> S2

To Remove:


NOTE: If the engine temperature is lower than 120 °F (48 °C), the H0<SUB>2</SUB> S2 sensor may be difficult to remove. Excessive force could possibly damage the threads in the exhaust pipe.

1. Raise and safely support the vehicle.
2. Disconnect the HO<SUB>2</SUB> S2 electrical connector.
3. Using an oxygen sensor tool carefully remove the H<SUB>2</SUB>0 S2.

To Install:

1. Coat the threads of the HO<SUB>2</SUB> S2 with anti-seize compound.
2. Using an oxygen sensor tool install the HO<SUB>2</SUB> S2.
3. Tighten the sensor to 30 ft lb (41 Nm).
4. Connect the HO<SUB>2</SUB> S2 sensor electrical connector.
5. Lower the vehicle.

firepop5

Thanks alot!

Mike Sigmond

you bet.

milwaukee_01impala

the upstream o2 sensor is on the rear exhaust manifold.

may i ask what you're inquiring about these for?

firepop5

This is my brother's car and he asked me for some help. He had his computer scanned at a parts store and they told him his O2 sensors were bad. Wanted to have as much info as possible before I start troubleshooting since I'm not familiar with the car. If I decide to swap out the sensors, is AC Delco worth the extra money or are Bosch replacements OK?

Mike Sigmond

What code(s) did it throw? They both may not be bad, it could even be something else.

firepop5

I got to see my brothers car today. The "Service vehicle soon" message is showing on dashboard. I scanned the OBD2 connector and got no codes. I would suspect if his O2 sensors were bad, the "check engine" light would come on instead of the service vehicle soon light anyway. I don't know why the shop he visited said he needed Os sensors. I saw their diagnostic report, and there are no codes listed, just a quote to change the O2 sensors.

According to his owners manual, if the service vehicle soon message appears, you must visit the dealer, or there is a problem with a trunk safety system. I'm pretty sure the car doesn't have this safety system on it.

After a little research I suspect the Body Control Module (BCM) is turning on the light. Does this BCM have a diagnostic connection and would an Auto Zone or similar place be able to diagnose or pull codes?

milwaukee_01impala

no, autozone or any other parts store wont be able to read BCM codes. you'll most likely have to got to a dealer to get those codes as those codes can only br read with a tech II scanner. the only place i've seen with a tech II is a dealer. you dont have to take it to a chevy dealer, any GM dealer will have a tech II scanner.

firepop5

Ared the BCM codes also accessed from the OBD2 terminal under the dash?