The causes for a P0403 EGR code could be any of the following:
Bad EGR solenoid
Excessive resistance in control circuit (PCM controlled ground) due to an open, chafing or damage to the harness
Poor connection at the EGR solenoid harness (worn or loose pins)
Water intrusion at the EGR solenoid harness
Blockage in EGR control solenoid holding solenoid open or closed causing excessive resistance
Loss of supply voltage to EGR solenoid
Possible SolutionsWith the ignition on and engine off, use a scan tool to activate the EGR solenoid. Listen or feel for a clicking, indicating that the solenoid is operating.
If the solenoid does operate, you'll have to check current draw on the ground circuit. It should be less than one amp. If it is then the problem is intermittent. If it isn't then there is excessive resistance in the circuit and perform the following
1. When it's activated see if you can blow lightly through it. IF you can 't there may be a blockage causing excessive resistance. Replace EGR solenoid as needed. If there is no blockage, disconnect the EGR solenoid and the PCM connector containing the EGR solenoid control circuit. Using a digital Volt-Ohm meter (DVOM) check resistence between the control circuit and battery ground. It should be infinite. If it isn't, then there is a short to ground on the control circuit. Repair the short to ground and retest as needed.
2. If the solenoid doesn't click as it should, disconnect the EGR solenoid connector and connect a test light between the two wires. Using the scan tool, command the EGR solenoid on. The light should light up. If it does, replace the EGR solenoid. If it does not perform the following: a. Check for 12 Volts on the ignition supply voltage to the solenoid. If it isn't present, inspect the supply circuit for an open, or a short due to chafing or breakage and re-test. B. If it still doesn't operate: then manually ground the EGR solenoid control circuit. The light should light. If it does, repair open in EGR solenoid control circuit and re-test. If it doesn't, replace EGR solenoid.
Sunday, February 20th, 2011 AT 12:28 AM