Can obdii - o2s12 % n/a

[ChevMali99]

Hello everyone,

Got some free time and figured why not find out what that code actually means. The Chilton book on Malibu 99 3.1L says in summary HO2S-1 is the O2 sensor 1 located on the exhaust manifold (behind the engine) & HO2S-2 is the O2 sensor 2 located on the outlet of the catalyst converter (by the actual exhaust pipe).

Here's the issue: My OBDII scanner (UIFTech U581) refers to the sensors as O2S11 & O2S12, that is not the puzzling part. What is puzzling is the fact that the S11 gives an actual percentage reading and the S12 gives a percentage reading of N/A (not applicable), is such reading accurate or is there supposed to be an actual voltage reading?

I read the manual, searched the net, and visited the manufacturers site (wouldn't you know it? is in Chinese) and all list as an example O2S12 % N/A.

Another thing, I've forever had the P0410 & P1404 codes in this car. I've learned to ignore the check engine light because, well nothing seems to get rid of it or them codes; nothing except 94 Octane and fuel injection cleaner. This time, however, I haven't done thing out of the ordinary & the MIL has been off for the better part of a month, yet the codes remain in the computer. Why? What causes the MIL to go off with codes remaining?

No, the MIL is not disabled, nor has the fuse blown.

Thanks to all for all your help through the years.

[Tech II]

Here's the issue: My OBDII scanner (UIFTech U581) refers to the sensors as O2S11 & O2S12, that is not the puzzling part. What is puzzling is the fact that the S11 gives an actual percentage reading and the S12 gives a percentage reading of N/A (not applicable), is such reading accurate or is there supposed to be an actual voltage reading?


% reading? It usually varies from 0.800 to 0.100 volts.......data for both sensors is in volts.....live data, the S11, bank 1 , sensor 1, will constantly be changine......the S12, bank 1, sensor 2, will not vary as fast as the front.....

I read the manual, searched the net, and visited the manufacturers site (wouldn't you know it? is in Chinese) and all list as an example O2S12 % N/A.

Another thing, I've forever had the P0410 & P1404 codes in this car. I've learned to ignore the check engine light because, well nothing seems to get rid of it or them codes; nothing except 94 Octane and fuel injection cleaner. This time, however, I haven't done thing out of the ordinary & the MIL has been off for the better part of a month, yet the codes remain in the computer. Why? What causes the MIL to go off with codes remaining?

In some cases, the CE light only comes on, if the test fails two drive cycles in a row.....if it only fails once, then passes, then fails, it won't turn the light on, For P1404, if you have a scan tool, look at the EGR position, at idle in park.....should be 0 %....if it is reading 3% or more, could be dirt under the pintle, the PCM may need a reprogram, or you have a bad pintle sensor in the EGR....

For P0410, you observe the S11 data on a cold start, when the air pump comes on......the S11 should read lean(stay lean as long as pump is on), and then when the pump shuts off should go rich, and then when close loop happens, should vary hi-lo....