Technical Description of OBD-II Trouble Code
Control Circuit for Exhaust Gas Recirculation “A”
What does that signify?
This diagnostic trouble code (DTC) is a generic powertrain code that is applicable to vehicles equipped with OBD-II. Although it is a generic code, the specific repair steps may vary depending on the make and model of the vehicle.
The Exhaust Gas Recirculation (EGR) system is controlled by a vacuum solenoid. The solenoid receives ignition voltage. The Powertrain Control Module (PCM) controls the vacuum solenoid by grounding the control circuit or driver.
The primary purpose of the driver is to provide ground for the controlled object. Each driver has a fault circuit that the PCM monitors. When the PCM activates a component, the voltage on the control circuit is low or close to zero. When the component is deactivated, the voltage on the control circuit is high or near battery voltage. The PCM monitors these conditions, and if it does not detect the proper voltage at the appropriate time, this code is set.
Potential Symptoms
Usually, a fault in the control circuit does not exhibit noticeable symptoms other than the illumination of the Malfunction Indicator Lamp (MIL). However, if the EGR control solenoid is stuck open due to debris or other factors, the code may be accompanied by misfire under acceleration, rough idle, or engine stalling.
Causes
The potential causes for a P0403 EGR code could be any of the following:
Possible Solutions
With the ignition on and the engine off, use a scan tool to activate the EGR solenoid. Listen or feel for a clicking sound, which indicates that the solenoid is operating.
If the solenoid operates, you will need to check the current draw on the ground circuit. It should be less than one amp. If it is, then the problem is intermittent. If it is not, there is excessive resistance in the circuit, and you should perform the following steps:
1. When the solenoid is activated, try blowing lightly through it. If you cannot blow through it, there may be a blockage causing excessive resistance. Replace the EGR solenoid if necessary. If there is no blockage, disconnect the EGR solenoid and the PCM connector containing the EGR solenoid control circuit. Use a digital Volt-Ohm meter (DVOM) to check the resistance between the control circuit and battery ground. It should be infinite. If it is not, there is a short to ground on the control circuit. Repair the short to ground and retest as necessary.
2. If the solenoid does not click as it should, disconnect the EGR solenoid connector and connect a test light between the two wires. Use the scan tool to command the EGR solenoid to turn on. The light should illuminate. If it does, replace the EGR solenoid. If it does not, perform the following steps: a. Check for 12 Volts on the ignition supply voltage to the solenoid. If it is not present, inspect the supply circuit for an open or a short due to chafing or breakage and retest. b. If it still does not operate, manually ground the EGR solenoid control circuit. The light should illuminate. If it does, repair the open in the EGR solenoid control circuit and retest. If it does not, replace the EGR solenoid.
Related EGR codes: P0400, P0401, P0402, P0404, P0405, P0406, P0407, P0408, P0409
