On my Monte Carlo I got this yesterday. This is the first time it has set this code. Usually I get a misfire and slow O2 (which I know exactly what those problems are), but this one has me thrown for a loop. I hope it's not the A.I.R. pump. Any suggestions?

 

P0300 is the code for Random Misfires, not the secondary air injection.

Sorry, no suggestions

 

Whhopps, yea, which is the other code I get and I know what that problem is. Typical of the 3.4L V6.

It must've been a P0419 then.

 

^^^

 

Once again...^^^

 

Well, not that anyone cares as I can see ALL the replies here, but I think I figured out the genesis of my problems.

Last Saturday I went to Elmhurst Chevy, probed GM's SI2000 system and pulled all info on DTC P0410 "Secondary Air Injection" system. For 1996 Monte Carlo Z34's with the 3.4L DOHC V6, it's 0410, NOT 0419 like on www.obdII.com

Anyway, I started going through their troubleshooting list, and step #3 is to test HO2S B1S1 response. Since I was also getting a slow B1S1 response code, I knew I had something here.

With the ignition on, engine off, on TechII or A-tap, the HO2S should drop below .200mv when cold (open loop). After 5 minutes, it only dropped to .305mv. So right there I knew something was wrong.

So I drove it for an hour and logged both B1S1 and B1S2's. Once warmed it, it seemed to work fine. But I think that under cold/open loop startups, it is setting off a chain reaction, those being P0305 "Cyl# 5 misfire detected" and P0300 "Random/multiple cylinder misfire" as well as the occasional P0410.

I will be replacing the B1S1 O2 sensor this weekend and monitor it from there.