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Hello and welcome! My name isCustomerand I would like to assist you with your question. Do all of the sensors that get a V ref with the key on have a FULL 5 volts going to them?
This would include the Yellow wire running from pin 9 of the C1381e PCM connector to the Throttle Position sensor, the Yellow/Green wire running from pin 52 of the PCM C1381b connector to the Air Conditioning Pressure sensor, and the Brown/Blue wire running from pin 66 of the PCM C1381b connector to the Fuel Tank Pressure sensor.
Check fuses 75, 76, and 78 in the engine compartment fuse box, and verify both sides of all three fuses show full battery voltage with the ignition on. How much voltage do these fuses have on them with ignition on?
Thank you for that information. I would check to be sure none of those V ref sensors are not shorted out as this can cause this problem. Start unplugging them one at a time and see if the 5 volts comes back. If not, then we need to go directly to the PCM and check the powers and grounds going into it with the key in the ON or RUN position.
Ok, then the PCM should be sending out the 5 volt reference with the key on. Which pins did you check for power and ground?