[ImperialCrown]

The MAP (P0106 and P0108) and TPS (P0122) all run on the 5 volt supply from the PCM (P1496).
Solve for P1496 and it should solve all the fault codes.
The 5 volt supply is a Pk/Yl wire out of the PCM. It changes to an Or/Pk at an intermediate connector (C102) on its way to the MAP sensor. It remains a Pk/Yl wire through a harness wire splice (S116) on its way to the TPS.
It is either being pulled low to ground by a component listed in the Possible Causes below or the PCM itself isn't able to supply it because of an internal failure.
What do you measure at the sensors in the way of supply voltage?

P1496-5 VOLT SUPPLY, OUTPUT TOO LOW​

When Monitored: With the ignition on.​

Set Condition: The 5-volt supply to the sensors is below 3.5 volts for 4 seconds.​

POSSIBLE CAUSES​

INTERMITTENT CONDITION​

THROTTLE POSITION SENSOR​

MAP SENSOR​

A/C PRESSURE SENSOR​

EGR SOLENOID​

5 VOLT SUPPLY SHORTED TO GROUND​

PCM

 

[ImperialCrown]

The 5 volts out of the PCM is low current and wouldn't have the Amperage required to burn wires, but adjacent wires melting other wires together could cause problems.
Separate the burnt wires. Repair or replace them as necessary. A salvage yard donor van and a good service manual with engine compartment wiring diagrams would be helpful to get things back the way that they were.