: 96 deville error codes P0147 and P0146, where do I look?

08-14-04, 03:59 PM
I had the OBD2 scan and came back with P0146 and P0147, O2 sensor circuit , no activity detected and o2 sensor heater circuit malfunction (bank1 sensor 3). I had replaced the O2 sensore about 2 months ago when I had error code P0145 (i believe) and the service light went away for about 1 day and then its been back ever since. based on these 2 codes, I have 2 questions: 1. Where is the sensor located adn 2. Is it the same sensor for both codes? to where I can assume it is a wiring problem possibly due to corrosion or a breakage. Any suggestion is appreciated, Thanks.

08-14-04, 04:55 PM
Those codes are both for the oxygen sensor after the catalytic converter. It may be in need of replacement, but if that's the same sensor they replaced before, check out the wiring first. Sounds like you know that already.

Maybe you know this stuff, but there are 4 heated oxygen sensors, at least on 96 and newer Northstars (and many other engines as well for OBD-II and emissions requirements). There is one on the exhaust manifold for both cylinder banks, one before the catalytic converter, and one after the cat. The one that seems to go out most frequently is the one before the catalytic converter. Don't know why, but 4 out of 5 Northstar owners I know have replaced that one first. Anyway, the point is the one before the cat may be the one that was replaced last time. This time it may be the one after the cat, and it's just a coincidence that the two failed in such close proximity.

I, and everyone else I know, have always had fine luck with the aftermarket Bosch oxygen sensors. I've heard disparaging remarks made about them here, but they seem to work just perfectly as far as I can tell. The OEM sensors are probably a bit more pricey. I think the last Bosch I bought for my car was about $75. I've also heard the argument that you should change all 4 at the same time. I think that's horse puckey and you should save your money. Replace them when they go bad. Usually they won't all go bad at, or even near, the same time.

Hope that helps... It's a few facts and a lot of opinions. Let us know how things work out with this.

Michael Cowden

08-15-04, 12:51 AM
That sounds like it could be the problem, unfortunately I don't want to go through the 2 more retest I have for emiissions just guessing that it could be 1 O2 sensor so i guess I should replace the other 3. The one that I had replaced was the one in front of the CAT on the passenger side. So that tells me that as far as "BANK",it must me bank 2. And since I have the error code for Bank 1 Sensor 3, I assume it is 1 sensor at the opposite bank, I guess but I want some more insight if anyone can help. I'd hate to take it to a shop where they will rip me off for just a simple thing as replacing sensors. If I can get more suggestions I would appreciate it.

08-15-04, 01:17 AM
I don't think you understand... The code is *definitely* for the O2 sensor after the catalytic converter. That means the sensor furthest from the engine. Both of the codes are for the same sensor. No question about it. No diagnosis or retesting necessary. It's either the wiring or the sensor itself more than likely. If neither of those is the case, it could be the PCM (very unlikely).

Does that clear it up?

08-17-04, 04:04 AM
Your codes point to the after cat sensor...the after cat sensor should show very low data voltage. You do not expect the after cat voltage to swing like the up stream O2 sensors..what you want to see is low voltage all the time...it shows the cat is scrubing the exhaust gas...

So either a bad cat or bad after cat sensor.

With OBDII...use the factory parts. I personally have spent time chasing codes just like this with aftermarket parts.

Logan Diagnostic

08-18-04, 12:26 AM
well I replaced the after cat sensor and no more lights on DIC. Now I can go to retest with confidence. By the way thanks to MCOWDEN for the clarification.

08-18-04, 08:42 PM
Excellent! Glad it worked out for you mookdawg...

Cheers! :cheers:

Michael Cowden