Okay so this is my first time posting on here. I've been having a problem with my ram, it's a 2001 quadcab with a 5.9, originally had a 5.2. When I swapped the motor I ran the 5.2 pcm no issues, all of a sudden I got a code saying it was internally failing, p0601? I think? I bought a new to me pcm out of a 2001 5.9 truck and it works but I get a code for a 02 sensor high voltage. I've replaced the sensor and still have the problem, truck also idles real low and will idle so low it will die. I used a scan tool to check and the voltage slowly climbs to 1.3 volts but if I high idle it , it switches and runs fine. The voltage is also fine while driving and it runs way better with this pcm, just doesn't at idle. Anyone have any ideas? I'm using ntk sensors and have no exhaust or vacuum leaks. I've tried my buddy's pcm and I have the same problem but it works with the old 5.2 one.

 

Could be a wiring issue or a bad O2 sensor. Was the PCM VIN flashed?

 

I was thinking wiring but it works fine with the old pcm, I've swapped the sensor twice and still same issue. Pcm was never vin flashed but using a scan tool it shows the correct vin so maybe it picked it up from somewhere or my scan tool did it automatically?

 

There are some differences in the configuration between California, federal and HD (2500/3500) emissions, most notably CA 1500s have 4 oxygen sensors. Also both the 98 and 01 FSM show different pins being used for O2 sensors between HD and non-HD (although I find that hard to believe). Could be the replacement PCM does not perfectly match. Do you know where it came from ? What's the part number ?

 

From my experience testing O2 sensors with a digital volt meter the voltage they put out varies quite a bit and not slowly as you describe. The voltage moves from .1 to .9 volts constantly.

 

it should have came from a federal truck. I live in CT so there really isn't any California emissions trucks. The number is 56028544AB which i found is for a 5.2 not 5.9 but that still doesn't explain why the o2 has issues. And it only doesn't with my pcm any other one it does.

 

it does switch from. 1 to .9 while driving but at idle it sticks at. 5 and then starts to climb to 1.3 volts in about a minute. Then the truck idles real low , has a really massive lope in the idle and sometimes will even die. But if i touch the gas barely it will rev up to 2k and hold there for like 10 seconds and then go back to its real low idle

 

Yes that number comes out to 5.2 federal emissions before 6/26/00. The manufacturing date of your truck is on the sticker in the door jamb, I'm not aware of any other changes I'd guess it's just different programming. IIRC NY state already required CA emissions back then so depending on where the truck was originally sold it may be CA emissions. The emissions label under the hood has that information. Or what is the part number of the original PCM ?