Code p1751 - 2001 Mitsubishi Montero Sport 4WD

1700 is a generic code for many makes and models referring to a transmission issue.1751 is directed to the shift solenoid valve b. May be able to replace just that solenoid and be ok. Cheaper than a transmission.

no make ,model , year mentioned ( essential information for close answers)
code p 1751 refers to AT-shift solenoid 1--open circuit ===causes wiring ---shift solenoid
if you have an automatic and there are shifting problems check it out --replace shift solenoid 1

SOUNDS LIKE SHIFT SOLINOIDS HAVE GONE BAD

P 1751 Shift Solenoid" A" performance. The solenoid is part of the transmission valve body and yes if this solenoid fails you will get limp mode.The only solution is a new solenoid may be even the wires to it or even the transmission module

All of the shift solenoids are located inside the transmission attached to the hydraulic control valve body, to access them you must remove the pan located on the bottom of the transmission.

this obd2 trouble code table may help you understand the meaning of code.

P1751 A/T Control Relay>>>Check power circuit to automatic trans (A/T) control relay, AND RELAY ITSELF FOR PROPER OPERATION!!

p1751= auto transmission control relay malfunction.according to mitsubishi it's 1 of 3 things.pretty straightforward.either the relay is bad,loose connector,or failed pcm (powertrain control module.

my mitshubishi lancar petrol car is consuming more fuel and giving black smoke

Assume you have tried earseing those codes and they keep coming back?
May have a loose or bad ground the engine harness sensor circuit.