I have a 95 se , k code. says PROM error for ses light coming on. Went and changed the whole ecm with the same Prom chip numbers on it , BNWB 1621 5814.
Cleared the ses code and drove about 2 blocks and the ses came back on and started running rough again?? The second scan resulted in a prom error and misfire detected?

So I put in new plugs and wires cuz the motor was used when I got it. Cleared the codes and the Prom error came back but no misfire detected code????? :?:

So I thought the used ecm was bad so I got another one and the same thing is happening. Is there something causing the ses code to come on for a Prom error even though the Prom is fine??? Thanks a million for any input!!!!!

P300 was the misfire but I cant find the P code for the prom error on the net or remember what it was?
I swapped the whole complete ecm twice with one with the exact same prom number that my original ecm had in it. After that I swapped the 2 other proms into my original ecm with no luck on either try. I cleared the codes after each ecm swap and each time I swapped the prom'*. I had ses light for knock sensor 1 failure and changed the knock sensor 1 day before the prom error code came on.

o.k. , whats the solution???? There is no way I have gotten 2 bad proms still intact in 2 different ecms. :?: :?: :?: :?:

This is all I could find on the prom error. Sorry I couldn't be of more help.
Tim

1994-99 Vehicles

Using a Tech 1® or equivalent scan tool, perform the on-board diagnostic system check.

Start the engine and run for one minute.

Scan for DTCs using the Tech 1® or equivalent scan tool, as outlined later in this section.

If Trouble Code P0325, P141, P120, or P1623 occurs, or if the MIL (Service Engine Soon) is ON constantly with no Diagnostic Trouble Codes (DTCs), the PROM or KS module is not fully seated or is defective.

If it is not fully seated, press firmly on the ends of the PROM/KS module.

Thanks for the replies!

I have had this P1623 prom error code trip twice now (first time was in 2011, 2nd time a week ago) and both times the problem was solved. The first time was after a rebuild (new valves, lifters, pushrods, head gaskets, etc.) on my sister'* '95 oldsmobile 98 regency elite 3.8L series 2. The car has one of those bizzare OBD1/OBD2 hybrid systems (OBD2 connector with an OBD1 software computer). The engine ran horrible and this was the only DTC code when the CEL came on. After lapping the new valves in the heads for a better seal the engine ran great and the code cleared.
This time we replaced a cracked head. Same P1623 code and engine was misfiring. After replacing a corroded injector wire on cyl. 4, the code cleared, CEL went off, and engine runs great.
Never had any problem with the ECM (PCM?) or its prom chip. Just seems to pop up when we have a consistent misfire. I thought it was a communication error between the computer and our scanner at first but I unplugged the ECT sensor temporarily and the correct code popped up.
I hope this helps someone out because I have never been able to find any solutions online!