Newby HELP! Power down @ 1900 RPM

Here's my story bought my 1st Diesel, unknown to me it had a cracked 53 block. Ran good but high idle (about 850 rpm). Bought a used 2000 24valve with 50 k miles on it. Did the re n re myself all went good runs good but @ 1900 RPM powers down, no throttle resonse until the RPM drop below 1900. Replaced fuel pump as it was producing 6-7 PSI. Traded the new engine ecm for the old ecm, starts, runs high idle like old engine for a few seconds then tach stops working, idle drops to a lower RPM and check engine light comes on ....but when test drove didn't power out at 1900 RPM....switched back to newer ECM and runs as normal except still powering out at 1900 RPM which takes it down the road at about 65mph. Accelerating onto freeway is done gradual as long as I don't hit the dreaded 1900 RPM I have power..NOTE it will rev to the redline when in park. Codes?? no check engine light on ...how can I check for codes??

Thanks 2 everyone for your help and suggestions

1999 2500 4x4 short box auto. 53 block 24valve just tossed and replaced with 2000 24valve. BHAF, BD Diesel Flow Max fuel pump, intank pump tossed

Edited January 10, 201015 yr by Mopar1973Man

You need a scan tool... Sorry... 1998.5 and 1999 can't use the key trick... The codes are the key here...

Welcome to the forum.

are the MAP sensors different between those year models? i know various fueling box come with adapters. and even mopar1973man says that it does report correctly to his scangauge. i agree with mopar1973man. get a scan tool that gives you live info. if you have a laptop, getting a tool that is usb could be invaluable.please keep us updated on your swap

Thanks to all ...will either get it scanned or a scanner this coming week and keep you posted...prefer hands on if I can after replacing the engine and fuel pump system am becoming very familiar with my 1st Diesel

My favorite scanner been a ScanGauge II nice little tool for scaning error codes and showing live data from the computers...

My gess is no tail shaft speed input. Will kill the engine at 1900 untill you give it one.