I have a 2001Monte SS that began having a miss. I replaced the plugs and wires....still had the miss. I replaced two of the three coil packs (for the cylinders that were showing the miss) and still it ran rough. A code for the EGR came up, so I replaced that...still was running rough. I went to ZZP and got a new PCM......still running rough. Bowed to the inevitable and took it to my mechanic, who told me that the catalytic converter was badly clogged. He replaced that and now it's running smooth, except now the engine light comes on with P0412 and P0418 codes showing. It's my understanding that these codes are related to the air pump, but my Monte doesn't have an air pump, so is this something I can ignore and how can I get the codes to stay clear? My thought was that maybe the new PCM was looking for an air pump connection and, when it couldn't find one, it started throwing a code for the solenoid. Is that possible? Thanks, in advance, for any help I can get.

 

Unless you, or the Previous Owner had it removed, there is an Air Pump on your motor.
From 1986 on, all GM computer controlled engines have an Air/Smog Pump. I know that my 86 Firebird 2.8, 87 IROC 350, and my 98 Monte LS all had an Air/Smog pump. And my 02 SS has one. Sounds a little strange to me that all years but 01 would have one. And I was able to pull up the air pump for 98 to 05 Monte Carlo SS 3800 motor.
https://www.rockauto.com/catalog/x,c...,parttype,4920

I recommend putting your old PCM back in. If the code does not come back, them maybe your pump was removed and those codes removed from your computer. If it does come back then you need to replace your air pump.
Hope this helps you out. Good Luck!

 

There is a California emissions option and I've seen 3800 and 3400 engines with it. It's an additional air pump assembly. On a 3800, some of this assembly is on the back of the engine (bolted to the same bracket that holds the engine cover). On the 3400, part of this set up is bolted to the front of the engine.

There are controls in the PCM for this. If you got a replacement PCM, it's possible it's got incorrect settings for your monte.

I would recommend contacting zzp (where you said you got the PCM). Or you can try your original PCM.

 

Thank you for your quick responses...much appreciated. A mechanic friend of mine and I, looked over my car and found that it does't have an A.I.R. pump and it came that way from the factory. The fuse and relay covers have the notations for the related fuses and relays for an A.I.R., but they are represented by dotted outlines and there are no metal pieces to allow for a connection with the relays and fuses, if there were any. Fortunately, since my last posting, it appears that the PCM has caught up with that fact and has stopped sending the codes. (At least for the moment...lol). Thank you again for your help. On another note, I have a wheel speed sensor code coming up...the hubs are still good, so I hate the idea of replacing them, just to get new sensors, so, is there any way I can clean the sensors and see if that works? I've seen a video on YouTube, where a guy does this on a Grand Am and it seems to work. I was just curious as to whether that would work for all makes and models, or just that particular one?