P0505 Error Code: Idle Control Valve Circuit Issue - 2000 Dodge Durango 5-9L
I'm currently experiencing a recurring check engine light and fault code P0505 in my 2000 Dodge Durango with a 5.9L V8 engine. I purchased the truck from an old friend who mentioned it needed smogging and had an underlying issue—so I bought it for $1000 with the hope of fixing it myself. Two months have passed, and despite multiple attempts to resolve the problem, the P0505 code keeps returning. I've already replaced the Idle Air Control Valve (IACV) twice. The battery has been tested by two independent load testers and shows no issues. All vacuum lines are new and leak-free. The wiring harness connecting to the IAC valve has been repaired, and the electrical system between the Powertrain Control Module (PCM) and the IAC has been checked for shorts or voltage fluctuations. The throttle body is clean with no oil residue in the intake manifold. The P0505 code typically reappears within a few hours of driving. Occasionally, it remains dormant for up to 24 hours, but it often returns immediately after clearing the code and restarting the engine. Until recently, both the error code (P0505) and the MIL (Malfunction Indicator Lamp) were active simultaneously. In recent events, the P0505 code has appeared while the MIL remains off. Given this pattern, I suspect the issue may be originating within the PCM itself. Before investing in a new control module, I'd like to know if there are any recommended diagnostic steps or electrical tests that could help identify whether the problem lies with the PCM or another component. Any insights or troubleshooting tips would be greatly appreciated.
Here’s a step-by-step approach based on common P0505 diagnostics for this vehicle: 1. Clear the fault codes using an OBD2 scanner. 2. Disconnect the Idle Air Control Valve (IAC) and start the engine. This may trigger other IAC-related codes—ignore those temporarily. 3. If the P0505 code does not return after restarting, it likely indicates a faulty IAC valve with internal shorting in one of its circuits. In this case, replace the IAC valve. 4. If the P0505 code returns after disconnecting the IAC, then the issue is not with the IAC motor itself. Proceed to visually inspect the wiring harness from the IAC all the way back to the PCM. You may need to strip the insulation off individual wires to check for shorts between conductors or to adjacent wires. This method has proven effective in similar 2000 Dodge Durango cases with P0505 codes. If no physical faults are found, it’s possible that the Powertrain Control Module (PCM) is malfunctioning and may require replacement. Always verify with a scan tool for live data during idle operation to support diagnosis. Reference: P0505 OBD2 Code Explanation