Cal pack prom info needed

[90RedBurb]

Can someone please explain to my simple brain what the function is of the 2 chips in the Tbi computer? The prom I believe contains the vehicle specific info needed ( engine size, trans, emissions equipment etc) for the truck to run right but what does the smaller chip (cal pack?) do? Reason I ask is through my quest of fixing an intermittent code 42 problem I changed computers and with my original 2 chips (asdz prom) it ran the same but when switching to a different set of chips (arjt prom) it seemed to run better (no ses light for 2 days) but developed a cold start misfire for the first 30 seconds of run timewith this set. Is this something the smaller chip would control? I just don’t understand what the small chip actually does. Any help is appreciated. Thanks

 

[dyeager535]

The small chip is the CALPAK. It's what is used to run the system in "limp mode". Shouldn't have any bearing on your problem. If it is being used by the ECM (instead of the PROM) the ECM would almost certainly be throwing a code. Or many.

There must be something in the original vehicle application that is different enough for the two PROMS to act differently, I wouldnt put a lot of weight in thinking one PROM is bad and one is good based on cold engine performance. If the cold engine issue is consistent, it's likely a programming difference, not a fluke or something related to your original problem.

 

[90RedBurb]

Ok that makes sense. Thank you for clearing that up. I made some other changes and reverted back to my original cal pack and prom and I’m on day 4 now of no ses or codes which is longer than it’s went without the issue in the 4 or so years I’ve owned the rig

 

[dyeager535]

You searched pretty good for code 42 issues and solutions others have had?

Definitely frustrating digging through this sort of issue when it's not constant. But from everything I see, it's either distributor components or the wiring. Is that a separate coil? Perhaps the wiring between it and the ICM is having problems? I'd really make sure the connections are all clean, and if I was in there, check each wire for breaks or short to ground with a meter. But being intermittent, unlikely you'll see much in way of a meter reading. But connections you might see some corrosion, and you might see bad wires where they meet the connector.

 

[90RedBurb]

yeah i stripped the loom covering off the entire under hood engine harness and attempted to run my fingers along every wire as well as visually inspect each one and found 2 suspect locations. I repaired one but also changed distributors at the same time so im unsure which was the issue however so far the problem seams to be gone, ran out of time to repair the other but if the rain would stop long enough when im off work i will fix that one too. I have a 400 mile trip home in a couple days and we will find out if the gremlins stay away or not. I have some nice braided split loom of various sizes and tessa tape at home so when i get home i will doctor the harness all back up but for now it is just temp taped up and safed off