I bought a 05 CRD with a rod knock. Ended up changing the engine and got it running. The transmission is apparently in Limp mode with 2nd and 3rd gear only. It has a Timing belt kit installed, new 850cca battery, new Samco hoses, new fuel and air filter, trans filters (wix 58843) and ATF +4. Also did the Weeks kit with the MAF unplugged. Cleaned and installed 2 different MAP sensors. Has the 2nd gen fuel head. I checked the connection to the gateway and that seems fine, but there is corrosion on the outer, bottom of the gateway module and I plan on replacing it but haven't yet.
The codes are:

P0683 Glow plug control module to PCM communication circuit
U0146 Lost communication with Gateway "A"
P0102 Mass or Volume Air Flow Circuit Low input
P1140 EGR throttle control circuit open

Would the communication issues with the gateway cause a Limp mode with the trans? Or any other suggestions?
Thanks,

You will need to address all communication errors first - one method is to remove the connector to each module, examine it for oxidation\corrosion, if clean replace and seat it, then go to the next module - this burnishes the contacting elements, establishing reconnection

_________________
'05 CRD Limited
Pricol EGT, Boost
GDE Hot '11; EDGE Trail switched
SEGR; Provent; Magnaflow;
Suncoast T\C, Transgo Tow'n'Go switch;
Cummins LP module, Fleetguard filter, Filterminder
2.5" Daystar f, OME r; Ranchos; K80767's, Al's lifted uppers
Rubicons, 2.55 Goodyears
Four in a row really makes it go

I'll add that if you did the weeks kit without a GDE tune, you will always have the P1140 code. Also check and clean all the connectors on the tranny. If you get everything cleared on the engine and you are still in limp mode, you should throw a tranny code, but you will need a Chrysler DRBIII scan tool to read those. Here's to hoping you can resolve it with fixing just engine and/or connector issues.

One other thing to check- make sure it's full of fluid. Like almost too full. The dipsticks made by the Chrysler dipsticks are wrong.

Thanks guys, I will try checking all the connections.