Vehicle Application: 2003 Dodge Ram 1500 Pickup 4.7L, Vin N, Eng Cfg V8 2003 Dodge Ram 1500 Pickup 5.7L, Vin D, Eng Cfg V8
Customer Concern: The check engine light is on. The engine runs good. Tests/Procedures: 1. Verify that the hoses for the purge solenoid are routed correctly and not pinched or restricted in any way. This includes verifying the lines to make sure there is no liquid fuel or charcoal in the lines. Clean as needed or replace the lines as needed.
2. Verify that the canister purge solenoid will vary duty cycle when commanded to by the scan tool. Replace the solenoid if sticking.
3. At the Natural Vacuum Leak Detection (NVLD) assembly, which is located at the front of the charcoal canister, near the front of the fuel tank, backprobe the Orange wire with a voltmeter. Locate the vacuum line going to the canister and remove the line so a hand vacuum pump can be used to put vacuum on the line going towards the NVLD. The other line at the NVLD goes to the vent. Block the vent line. Using a hand vacuum pump, apply vacuum to the line while watching the voltage on the Orange wire. Voltage is supposed to change at approximately 1 inch Hg vacuum. Try testing this switch several times to see if the switch is sticking. Replace the NVLD if the switch is sticking. Potential Causes: Hoses Natural Vacuum Leak Detection (NVLD) Assembly Purge Solenoid