So, I have this long term project involving a 1998 Dakota 4WD Super Cab. When the 5.2l was getting tired I bought a 5.9L from a 1998 RT put it on an engine stand and slowly rebuilt it to a 408 and installed it. Now it runs great but I can't get it to pass California smog with either the 5.2L or the 5.2L PCM. I was going to the referee route and fess up to the swap so I bought an RT computer. Still runs strong and great but now I get CEL that tells me it is missing the second bank of O2 sensors. My harness doesn't support that as the original 318 only has single exhaust. Anybody know of a solution?

 

Put your 5.2 PCM back in and get it properly tuned. The 5.2 tune is close, but there are some differences that need to be cleaned up in the file, especially trying to make it run a cammed 408.

Reach out to Ryan at www.frptuning.com Flyin Ryan Performance. He's tuned several of these.

 

ALL of tehse trucks came stock with single exhaust. but it sounds like the truck is "49 state" compliant while the R/T computer is set up for that 50th state..... which had 2x the converters and 2x the number of O2's.

 

This would be correct. And it is not easily fixable without a major harness change.

Easier to use the original PCM and get it programmed to properly SMOG a 408.

Hell, there's (properly tuned) boosted 365's and 408s out there that are damn near cleaner in SMOG than a factory engine.