Is your vehicle idling at all? Usually when the Idle Air Control valve (IAC) has its electrical connector unplugged, or is malfunctioning in any way, the vehicle will be hard pressed to maintain an idle and, in fact, usually shuts off. The Power-train Control Module uses the IAC to maintain the correct amount of air to enter the intake manifold to keep the engine idling because the throttle plate is closed at idle. Air usually enters the intake manifold via the throttle body when the throttle plate is opened as one steps on the gas pedal. It is then mixed with the proper amount of fuel and burned in the engine's combustion process.
Okay enough of that, I have included for you in the diagrams below, a Diagnostic Troubleshooting Flowchart from the vehicle manufacturer on DTC 0505. You will need a multi-meter and possibly a vacuum pump to perform these tests. You can rent vacuum pumps at your local parts store free of charge. I have included a link below on how to use a multi-meter if needed.
Please go through the flowchart in the diagrams down below and get back to us with what you find out.
Images (Click to enlarge)
Wednesday, March 13th, 2019 AT 7:06 PM