What is this p1899 - 2001 Jeep Grand Cherokee

Some are easy fixes (O2 sensor), the fuel vapour ones need a bit of investigation, as does the Neutral Safety Switch..

P0135 JEEP Code - O2 Sensor Heater Circuit Malfunction ...

https://www.engine-codes.com > p0135_jeep
'P0135 JEEP code possible causes · Faulty Heated Oxygen Sensor (H2OS) Bank 1 Sensor 1 · Heated Oxygen Sensor (H2OS) Bank 1 Sensor 1 circuit fuse · Heated Oxygen ...

P0455 JEEP Code EVAP System Large Leak (With Video)

https://www.autocodes.com > p0455_jeep
May 30, 2020 - 'P0455 JEEP code tech notes ... The P0455 it's very common code because the code is set if the gas cap is loose or missing. Start by tightening ...

P0442 JEEP Code Evaporative Emission Control Small Leak ...

https://www.autocodes.com > p0442_jeep
May 30, 2020 - The P0442 code means that the control module has detected a small leak in the Evaporative Emission (EVAP). Loose fuel tank filler cap is the ...

P1899 JEEP Code - Park/Neutral Switch Circuit Conditions

https://www.engine-codes.com > p1899_jeep
'P1899 JEEP code possible causes · Faulty Park/Neutral Switch · Park/Neutral Switch harness is open or shorted · Park/Neutral Switch circuit poor electrical ...

The p1899 code is for a faulty park/neutral switch which is located on your transmission. Changing it involves disconnecting the wiring harness that goes to it, unbolting the switch, losing some transmission fluid, installing the new switch and topping the fluid off. Big problems arise from having too much or too little fluid in a transmission. Even a small amount or under the proper level can pose a threat. I'd take it to a repair shop and let them handle the job.

According to my source, code 1899 is a problem with the governor pressure sensor. But 4 digit codes are model specific, so you may be right about the selector switch.
If the switch tests out to be faulty, it would need to be replaced and the code erased.

try to reset.but if not why shows code.

P1899 Park/Neutral position (switch) stuck in park or in gear

http://www.aa1car.com/trouble-codes/chrysler_codes_p1400-p1899.htm

that code is "P/N Switch Stuck in Park or in Gear"

PARK/NEUTRAL SWITCH STUCK IN PARK it is p1899 you need the switch

P0743 is the Torque Converter Circuit Solenoid.The solenoid plug is on the front of the transmission and has a dark green/white and orange/black wire. The dark green/white should have 12V on it from fuse #10 when the ignition is on. The orange/black is a grounding wire from pin 79 of the powertrain controller which should only be grounded when the car is going over 45 mph or so. You could check that the wire is patent between the plug and the powertrain plug (near 0 ohms). The solenoid is a coil or wire so it would have a low, but non-0 resistance, maybe less than an ohm, but still not 0. To really test it you would need an impedence meter, but a good digital ohmmeter should show it to be slightly more resistance than is shown when you test the resistance of the meter leads themselves.If the resistance, the patency, and the 12V supply is all shown to be OK, then I would suspect the solenoid is not functing properly. If you are getting torque converter lock up when you accelerate slowly from 40 to 50 mph then it is working and the code is false. P1899 Park or neutral position switch stuck in park or gear. Recap: P0743 Torque converter clutch circuit faulty, P1899 Position switch to park and nutral stuck. Check the wire harness and look for any clips may be lose or disconnected and wires condition. Good luck and keep me posted. be glad to help

the neutral switch is on the trasmission on the shirter its not that hard to change good luck pierre