P0403 Exhaust Gas Recirculation Circuit Malfunction

DTC P0403 - OBD-II Data Sheet

• P0403 - Malfunction of the circuit of recirculation of exhaust gases "A"

What does code P0403 mean?

This Diagnostic Trouble Code (DTC) is a generic transmission code, which means it applies to OBD-II equipped vehicles. Although general, specific repair steps may differ depending on the brand / model.

The exhaust gas recirculation (EGR) system is controlled by a vacuum solenoid. Ignition voltage is applied to the solenoid. The powertrain control module (PCM) controls the vacuum solenoid by grounding the control circuit (ground) or driver.

The main function of the driver is to provide grounding of the controlled object. Each driver has a fault circuit that the PCM monitors. When the PCM turns on the component, the control circuit voltage is low or close to zero. When the component is turned off, the voltage in the control circuit is high or close to battery voltage. The PCM monitors these conditions and if it does not see the correct voltage at the correct time, this code is set.

Possible symptoms

Typically, a malfunction in the control circuit will leave no discernible symptom other than the Malfunction Indicator Lamp (MIL) illuminated. However, if the EGR control solenoid is stuck open due to debris, etc., the Code may be accompanied by a misfire on acceleration, abrupt idle, or a complete engine stop.

The symptoms most commonly associated with this error code are as follows:

• Turn on the corresponding engine warning light.
• Unstable engine operation.
• Starting problems.
• Acceleration problems.
• The engine suddenly stops.
• Bad exhaust smell.

Causes

The exhaust gas recirculation circuit performs the function of returning burnt gases to the circuit up to a percentage of 15%. This allows us to contribute to the reduction of emissions of harmful substances into the atmosphere. A special solenoid measures the exhaust gases that are re-circulated and also ensures that the EGR does not start until the engine reaches optimum operating temperature. The EGR solenoid is usually located on the intake manifold and uses vacuum from the engine to actuate the EGR valve, which in turn regulates the intake of exhaust gases. This device is powered by a 12-volt charger from the engine ECU. If the solenoid circuit shows signs of malfunction.

The reasons for the appearance of the exhaust gas recirculation system code P0403 can be the following:

• Faulty exhaust gas recirculation solenoid
• Excessive resistance in the control circuit (PCM controlled ground) due to open, abraded, or damaged wiring harness
• Bad connection in the exhaust gas recirculation solenoid valve harness (worn or loose pins)
• Water ingress into the exhaust gas recirculation solenoid wiring harness
• Blockage in EGR solenoid holding the solenoid open or closed causing excessive resistance
• Lack of supply voltage at the exhaust gas recirculation solenoid.
• Bad PCM

Possible Solutions to P0403

Ignition ON and engine OFF, use a scan tool to activate the EGR solenoid. Listen or feel a click to indicate that the solenoid is operating.

If the solenoid works, you will need to check the current drawn in the ground circuit. Must be less than one amp. If so, then the problem is temporary. If it is not, then the resistance in the circuit is too high, and proceed as follows.

1. When it is activated, see if you can easily purge it. IF you cannot do this, a blockage may occur causing excessive resistance. Replace the exhaust gas recirculation 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 ohmmeter (DVOM) to check the resistance between the control circuit and battery ground. It should be endless. If not, then the control circuit has a short to ground. Repair the short to ground and repeat the test if necessary.

2. If the solenoid does not click properly, disconnect the EGR solenoid connector and connect a test lamp between the two wires. Command the EGR solenoid ON with a scan tool. The light should come on. If so, replace the EGR solenoid. If it fails to do the following: a. Make sure the ignition supply voltage to the solenoid is 12 volts. If not, check the power circuit for an open or short circuit due to abrasion or open circuit and retest. b. If it still does not work: then manually ground the EGR solenoid control circuit. The light should come on. If so, repair the open in the EGR solenoid control circuit and recheck. If not, replace the exhaust gas recirculation solenoid.

Repair Tips

After the vehicle is taken to the workshop, the mechanic will usually perform the following steps to properly diagnose the problem:

• Scan for error codes with an appropriate OBC-II scanner. Once this is done and after the codes have been reset, we will continue to test drive on the road to see if the codes reappear.
• Check the solenoid.
• Inspect the EGR valve for blockages.
• Inspection of the electrical wiring system.

Rushing to replace the solenoid is not recommended, as the cause of the P403 DTC may lie elsewhere, such as a short circuit or valve malfunction. As mentioned above, the EGR valve can become clogged due to the accumulation of soot, in which case a simple cleaning of this component and its reinstallation will solve the problem.

Generally, the repair that most often cleans up this code is as follows:

• Repair or replacement of the solenoid.
• Repair or replacement of the EGR valve.
• Replacement of faulty electrical wiring elements,

Driving with DTC P0403 is not recommended as it can seriously affect the vehicle's stability on the road. Given the complexity of the inspections being carried out, the DIY option in the home garage is unfortunately not feasible.

It is difficult to estimate the upcoming costs, since a lot depends on the results of the diagnostics carried out by the mechanic. As a rule, the cost of replacing the EGR valve in the workshop, depending on the model, is about 50-70 euros.

Frequently Asked Questions (FAQ)

What does code P0403 mean?

DTC P0403 signals a malfunction in the exhaust gas recirculation (EGR) circuit.

What causes the P0403 code?

A faulty EGR valve, a faulty solenoid, and a faulty wiring harness are the most common triggers for this code.

How to fix code P0403?

Carefully check the EGR circuit and all connected components, including wiring.

Can code P0403 go away on its own?

Usually this code does not disappear on its own.

Can I drive with code P0403?

Driving with error code P0403, while possible, is not recommended as it can have serious consequences for the vehicle's stability on the road.

How much does it cost to fix code P0403?

On average, the cost of replacing an EGR valve in a workshop, depending on the model, is about 50-70 euros.

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