P0403 Exhaust Gas Recirculation Circuit Malfunction

Description and meaning of DTC p0403

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 driverThe primary function of the driver is to supply ground for the object that isbeing controlled. Each driver has a fault circuit that the PCM monitors. Whenthe PCM turns a component on, the control circuit voltage is low, or close tozero. When the component is turned off, the voltage on the control circuit ishigh, or near battery voltage. The PCM watches for these conditions, and ifit doesn\'t see the proper voltage at the proper time, this code is set.

p0403 diagnostic trouble code symptoms

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

DTC p0403 - possible causes

The causes for a P0403 EGR code could be any of the following:Bad EGR solenoidExcessive resistance in control circuit (PCM controlled ground) due to anopen, chafing or damage to the harnessPoor 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 causingexcessive resistance Loss of supply voltage to EGR solenoid Bad PCM

How to fix OBD-II diagnostic trouble code p0403

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 groundcircuit. 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 thefollowing 1. When it's activated see if you can blow lightly through it. IF you can\'tthere may be a blockage causing excessive resistance. Replace EGR solenoid asneeded. If there is no blockage, disconnect the EGR solenoid and the PCM connectorcontaining the EGR solenoid control circuit. Using a digital Volt-Ohm meter(DVOM) check resistence between the control circuit and battery ground. It shouldbe 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 solenoidconnector 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, replacethe EGR solenoid. If it does not perform the following: a. Check for 12 Voltson the ignition supply voltage to the solenoid. If it isn't present, inspectthe 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 controlcircuit. The light should light. If it does, repair open in EGR solenoid controlcircuit 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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