1996 Dodge Caravan van will not start

Sounds like the catalytic converter is plugged up. Get your PCM scanned and post the code numbers here.

Do this. Insert the key into the ignition and cycle the key to ON-OFF-ON-OFF-ON within 5 seconds, but not too fast either. This will set the PCM into diagnostic mode. Locate your odometer LCD display, and jot down the codes that being displayed, and post what you find out.

On a side note: You can't "clean" catalytic converter. I am not sure what was done, but if they have removed the internal parts of the cat, it will not work properly.

That works too. Your codes are 12, 24, 22 and 55.

12. Battery has been disconnected for the past 50 cycles. Nothing there.

24. Throttle position sensor voltage high.
22. Engine coolant temperature sensor voltage too high.

55. End of test.

Give me the engine size for proper diagnostic. 3.0, 3.3, 3.8. Gas, CNG, Flex.

TEST TC-27A - THROTTLE POSITION SENSOR VOLTAGE HIGH
1. Read throttle position sensor voltage. If voltage is more than 4.5 volts, go to step 6). If voltage is 4.5 volts or less, go to next step.
2. While monitoring throttle position sensor voltage, slowly open and close the throttle. If voltage does not change smoothly, replace throttle position sensor. If voltage changes smoothly, go to next step.
3. With throttle at closed position, wiggle wiring harness and connector going to throttle position sensor on throttle body while monitoring the voltage. If voltage changes while moving wiring harness, repair wiring harness or connector. If voltage does not change while moving wiring harness, go to next step.
4. Conditions required to set DTC are not present at this time. DTC may be stored in Powertrain Control Module (PCM) if throttle position sensor voltage at PCM terminal No. 35 is more than 4.5 volts. Possible causes are: sensor signal circuit open, defective throttle position sensor, sensor ground circuit open, defective PCM, defective connector terminals or wiring. Go to next step.
5. Check for defective wiring/connection at throttle position sensor and PCM. The PCM is located between driver's side front fender and power distribution center, near battery. If defective wiring/ connections exist, repair as necessary. If no defective wiring/connections exist, see INACTIVE TROUBLE CODE CONDITION.
6. Disconnect connector at throttle position sensor on throttle body. Install jumper wire between Orange/Dark Blue wire and Black/Light Blue wire on connector for throttle position sensor. Using scan tool, read throttle position sensor voltage.
7. If scan tool displays NO RESPONSE, repair Orange/Dark Blue wire for a short to the Violet/White wire. If scan tool displays a voltage of less than one volt, replace throttle position sensor. If scan tool displays a voltage of one volt or more, go to next step.
8. Remove jumper wire. Reconnect jumper wire between Orange/Dark Blue wire on connector for throttle position sensor and engine ground. Using scan tool, read throttle position sensor voltage.
9. If voltage is less than one volt, repair open circuit in Black/Light Blue wire (sensor ground). If voltage is one volt or more, go to next step.
10. Turn ignition off. Disconnect connectors from Powertrain Control Module (PCM). The PCM is located between driver's side front fender and power distribution center, near battery.
11. Using external ohmmeter, check resistance between Orange/Dark Blue on connector for throttle position sensor and PCM connector terminal No. 35 (Orange/Dark Blue wire). If resistance is less than 5 ohms, replace PCM. If resistance is 5 ohms or more, repair open circuit in Orange/Dark Blue wire between PCM and throttle position sensor.

TEST TC-31A - ENGINE COOLANT TEMP SENSOR VOLTAGE TOO HIGH
1. Using scan tool, read ECT voltage. If ECT voltage is more than 4.5 volts, go to step 7). If ECT voltage is 4.5 volts or less, go to next step.
2. Wiggle wiring harness and connector going to engine coolant temperature sensor while monitoring ECT voltage. Engine coolant temperature sensor is located near thermostat housing and contains a Black/Light Blue wire and a Tan/Black wire in the connector.
3. If ECT voltage changes while moving wiring harness, repair wiring harness or connector as necessary. If ECT voltage does not change while moving wiring harness, go to next step.
4. Conditions required to set DTC are not present at this time. DTC may be stored in Powertrain Control Module (PCM) if ECT voltage at PCM terminal No. 26 is more than 4.9 volts for more than 3 seconds. Possible causes are: sensor signal circuit open, sensor internally open, sensor ground circuit open, defective PCM, defective connector terminals or wiring. Go to next step.
5. Check for defective wiring or connections at engine coolant temperature sensor and PCM. The PCM is located between driver's side front fender and power distribution center, near battery.
6. If defective wiring or connections exist, repair as necessary. If no possible causes are found, see INACTIVE TROUBLE CODE CONDITION.
7. Disconnect connector at engine coolant temperature sensor. Engine coolant temperature sensor is located near thermostat housing and contains a Black/Light Blue wire and a Tan/Black wire in the connector.
8. Connect jumper wire between Black/Light Blue wire and Tan/Black wire in the connector for engine coolant temperature sensor. Using scan tool, read ECT voltage.
9. If ECT voltage is less than one volt, replace engine coolant temperature sensor. If ECT voltage is one volt or more, go to next step.
10. Remove jumper wire from connector. Reconnect jumper wire between Tan/Black wire in the connector for engine coolant temperature sensor and engine ground. Using scan tool, read engine coolant temperature sensor (ECT) voltage.
11. If ECT voltage is less than one volt, repair open circuit in Black/Light Blue wire (sensor ground). If ECT voltage is one volt or more, go to next step.
12. Turn ignition off. Disconnect connectors from Powertrain Control Module (PCM). The PCM is located between driver's side front fender and power distribution center, near battery.
13. Using external ohmmeter, check resistance between Tan/Black wire on connector for engine coolant temperature sensor and PCM connector terminal No. 26 (Tan/Black wire). If resistance is less than 5 ohms, replace PCM. If resistance is 5 ohms or more, repair open circuit in Tan/Black wire between PCM and engine coolant temperature sensor.

***My initial thought was faulty PCM, but you already have a new one, so that can't be it. So you need to get access to a scan tool for proper check engine light codes, instead of the generic ones that we have now. CSK/O'Reilly has a loaner scanner that you can borrow for a deposit.***