: O2 Sensors

11-03-09, 05:43 PM
Hi all, I'm new to the site I have been lurking for a short time so I figured it was time to join and as with most newbees I have a question.I own a 98 sts that has set a current code of p0146, if I'm not mistaken that is an 02 code for bank 1 sensor 3. Is this correct and if so which one is it,before or after the cat? Thanks for any and all help. Jerry

11-03-09, 08:31 PM
P0146 - Heated Oxygen Sensor (HO2S) Circuit Insufficient Activity Bank 1 Sensor 3
Bank 1 Sensor 3 is after the CAT.

11-03-09, 08:55 PM
Ranger THANK YOU.I just went outside and looked and the best I can tell I only have one and it's after the cat.Again thanks.J

11-03-09, 09:08 PM
Oops, I corrected my post. If you had a pre CAT sensor it would be Bank 1 Sensor 2. If you DID NOT have a pre CAT sensor (the one that was done away with) then the aft CAT sensor would be Bank 1 Sensor 2. Since your code came up as sensor 3, you must have a pre CAT sensor.

11-03-09, 09:22 PM
OK,so it will be the pre cat not the after cat?

11-03-09, 10:07 PM
No. Bank 1 Sensor 1 is the manifold sensor. Bank 1 Sensor 2 is the pre CAT sensor. Bank 1 Sensor 3 is the aft CAT sensor.

11-03-09, 10:24 PM
Ranger,Thanks again I'll be swapping it in the AM. :)

11-04-09, 10:30 AM
Check all your engine vacuum lines first - the connectors and lines to/from the throttlebody as well as the vacuum and fresh air PCV piping and connectors.

Most O2 codes are more likely to be set by vacuum leaks, but the after cat sensor monitors cat efficiency, so if you feel that your car has been acting sluggish lately you may have a problem concerning cat function.

As Ranger posted, S1 is the manifold sensor on each side, S2 is the pre-cat on a dual (cat) sensor system while S3 is the after-cat. In a single (cat) sensor setup, S2 is the after-cat unit.

Do not bend, twist, or cut the sensor wiring. Do not get anything on the new sensor tip.

12-03-09, 02:23 AM
So, where is the Bank 2, Sensor 1 on a '97 Eldo?

12-03-09, 09:16 AM
The top side of the front exhaust manifold.........Bank 2.

Northstars have an O2 sensor in each bank manifold as well as one or two after the collector Y - a pre-cat (S2) and an after-cat (S3) sensor - or maybe only an after-cat (S2) unit.

Look at it this way: Bank 1 is the odd-number cylinder side (1,3,5,7) and Bank 2 is the even cylinder side (2,4,6,8).