Changes O2 sensro (1/1) and now 2/1 is throwing code P0155

[shadow83]

My Galant threw I think it was code P0135, it was O2 sensor 1, bank 1. Changed the sensor today and the light was out but came on the next time I started the car, cleared the codes but it came back on later, code is P0155 02 sensor 1 bank 2. Has anyone had two sensors take a crap at the same time?

From what the manual said sensor 1/1 was on the front of the engine on the top behind the radiator, easy to replace. Sensor 2/1 looks like the same one but on the rear bank. I'm thinking of just trying to replace that one now and see.

[4g63lover]

it's not that unusual for both sensors to go out. they do go through the same conditions as each other on the daily. how many miles are on the car?

Most of the time the heater circuits just burn out.

[jubeiaire]

^^^ this and changing one sensor on the same run will give a pure reading while the other sensor is slightly clogged causing the computer to think that it is no longer good because it is reading different lvls than the other sensor.

[shadow83]

Car has 154k miles. The code is now P0154 2/1 Sensor is not working.

I ordered another Denso sensor this morning, cheaper to try $50 that pay a garage. I just hope the 2/1 sensor is as easy as the 1/1.

I just thought it unusual for the same upstream O2 sensor to go on the other bank. From what I found the 1/1 sensor is upstream of the cat on the front of the engine( cyl 1 head, radiator) and 2/1 sensor is upstream of the cat on the rear bank (#2 cylinder head. firewall)

[GarciaR88]

"From what I found the 1/1 sensor is upstream of the cat on the front of the engine( cyl 1 head, radiator) and 2/1 sensor is upstream of the cat on the rear bank (#2 cylinder head. firewall)"

I'm new to the whole O2 sensor's issue since I just bought a used '02 Galant V6. I think you have the last bit backwords:

Bank 1 Sensor 1: From front of car, would be on exhaust manifold closest to the firewall.
Bank 2 Sensor 1: From front of car, would be on exhaust manifold closest to the radiator.
Bank 1 Sensor 2: From front of car, would be below "mini" cat closest to the firewall. (Code P0141)
Bank 2 Sensor 2: From front of car, would be below "mini" cat closest to the radiator, under car.

The V6's definitely have 4 sensors.

Can anyone confirm or clarify?

[shadow83]

I just spoke with the dealer, you are correct, bank 1 is the rear bank closest to the firewall, the service manual is wrong.

Looks like I changed the wrong one, and the one that I did change is either bad or the connector needs cleaned. Can anyone tell me if the rear upstream sensor is as easy to change as the front?

[GarciaR88]

Should be. Remove the heat shield (three bolts, 13MM). Using a O2 socket should make it easier. Spray it with Liquid Wrench. I used the "Dry" spray. Sprays on wet then dries to a powder. Let it set for a few minutes.

[shadow83]

I saw it, it is easier than the front, no heat shield and stickin right out like a male dog smellin heat.

Turns out that I had the connector on wrong on the front sensor. It was getting dark and I couldn't see well. Duh!

[jubeiaire]

flash lights and drop lights for the win!!!

[shadow83]

Talk about spooky.

As above I changed the 2/1 O2 sensor by mistake, fixed the connector and reset the codes and no codes any more. The original code was for the 1/1 O2 sensor and now that code has not reappeared? I'm not complaining, just find it wierd. Usually when the heater circuit goes it is gone for good. Well, I have a spare O2 sensor so if the code pops again I am ready.