P0403 Exhaust Gas Recirculation Circuit Malfunction

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P0403 Exhaust Gas Recirculation Circuit Malfunction

OBD-II Trouble Code Technical Description

Exhaust Gas Recirculation "A" Control Circuit

What does that mean?

This diagnostic trouble code (DTC) is a generic powertrain code, which means that it applies to OBD-II equipped vehicles. Although generic, the specific repair steps may vary depending on make/model.

The Exhaust Gas Recirculation (EGR) system is controlled by a vacuum solenoid. The solenoid is supplied ignition voltage. The Powertrain Control Module (PCM) controls the vacuum solenoid by grounding the control circuit(ground) or driver

The primary function of the driver is to supply ground for the object that is being controlled. Each driver has a fault circuit that the PCM monitors. When the PCM turns a component on, the control circuit voltage is low, or close to zero. When the component is turned off, the voltage on the control circuit is high, or near battery voltage. The PCM watches for these conditions, and if it doesn’t see the proper voltage at the proper time, this code is set.

Potential Symptoms

Usually a fault in the control circuit, will leave no noticeable symptoms other than the Malfunction Indicator Lamp (MIL) illumination. However, if the EGR control solenoid is stuck open due to debris, etc. the code may be accompanied by misfire under acceleration, rough idle, or engine dying altogether.

Causes

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
  • Bad PCM
  • Possible Solutions

    With 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.

    Related EGR codes: P0400, P0401, P0402, P0404, P0405, P0406, P0407, P0408, P0409

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    "Delete Error Code Permanently, Disable DTC Error Code Function for p0403 in the ECU"

    In extreme cases, we even have the option to permanently remove the specific DTC p0403 and disable the function of the specific error code in the ECU. All other fault code functions will then continue to work to protect the engine. This is different from clearing an error code with a diagnostic device. We have the option to permanently remove the function of the specific error code, so that it never comes back. Also emergency running that occurs on the specific error code can be solved in most cases.

    Of course we prefer to first try to solve the cause of the error code, but sometimes the only solution is to permanently disable the DTC function of p0403.

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