P0405 Low indicator circuit of the sensor A of the exhaust gas recirculation system

OBD-II Trouble Code - P0405 - Data Sheet

Low signal level in the exhaust gas recirculation sensor circuit.

P0405 is a generic OBD-II code indicating that the Engine Control Module (ECM) has detected that the Engine Exhaust Gas Recirculation (EGR) sensor is out of range. Short to ground sensor input to ECM.

What does trouble code P0405 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.

There are different designs of exhaust gas recirculation systems, but they all work in the same way. The Exhaust Gas Recirculation Valve is a valve controlled by the PCM (Powertrain Control Module) that allows measured amounts of exhaust gases to pass back into the cylinders for combustion along with the air/fuel mixture. Because exhaust gases are an inert gas that displaces oxygen, injecting them back into the cylinder can lower the combustion temperature, which helps reduce NOx (nitrogen oxide) emissions.

EGR is not required during cold start or idling. EGR is energized under certain conditions, such as at start-up or idling. Exhaust gas recirculation is supplied under certain conditions, such as partial throttle or deceleration, depending on engine temperature and load, etc. Exhaust gases are supplied to the EGR valve from the exhaust pipe, or an EGR valve can be installed directly in the exhaust manifold. If necessary, the valve is activated, allowing gases to pass into the cylinders. Some systems direct exhaust gases directly into the cylinders, while others simply inject them into the intake manifold, from where they are then drawn into the cylinders. while others simply inject it into the intake manifold, from where it is then pulled into the cylinders.

Some EGR systems are fairly simple, while others are slightly more complex. The electrically controlled exhaust gas recirculation valves are directly computer controlled. The harness connects to the valve itself and is controlled by the PCM when it sees a need. It can be 4 or 5 wires. Typically 1 or 2 grounds, 12V ignition circuit, 5V reference circuit, and feedback circuit. Other systems are vacuum controlled. It's pretty straightforward. The PCM controls a vacuum solenoid which, when activated, allows the vacuum to travel to and open the EGR valve. This type of EGR valve must also have an electrical connection for the feedback circuit. The EGR feedback loop allows the PCM to see if the EGR valve pin is actually moving properly. If the feedback circuit detects that the voltage is unusually low or below the specified voltage, P0405 can be set.

Symptoms

Symptoms of a P0405 trouble code may include:

• MIL Illumination (Malfunction Indicator)
• The Check Engine light will come on and the code will be stored in the ECM.
• The ECM may open the EGR valve more than necessary if the voltage is too low, causing the engine to stall or wobble when accelerating.
• The engine's EGR system can cause the engine to run rough, oscillate, or even stall if it does not indicate the correct position of the EGR valve on the ECM.
• The ECM can block the valve from opening when it detects a malfunction, and the engine can pre-ignite on acceleration.

Causes of the P0405 code

Possible causes of a P0405 code include:

• Short to ground in EGR signal circuits or reference circuits
• Short circuit to voltage in the ground circuit or signal circuits of the exhaust gas recirculation system
• Bad EGR valve
• Bad PCM wiring problems due to abraded or loose terminals

Possible solutions

If you have access to a scan tool, you can command the EGR valve ON. If it is responsive and the feedback indicates that the valve is moving correctly, the problem may be intermittent. Occasionally, in cold weather, moisture can freeze in the valve, causing it to stick. After warming up the vehicle, the problem may disappear. Carbon or other debris can get stuck in the valve causing it to stick.

If the exhaust gas recirculation valve does not respond to the scan tool commands, disconnect the exhaust gas recirculation harness connector. Turn the key to the on position, the engine is off (KOEO). Use a voltmeter to check for 5 V on the test lead of the EGR valve. If there is no 5 volts, is there any voltage at all? If the voltage is 12 volts, repair the short to voltage on the 5 volt reference circuit. If no voltage is present, connect a test lamp to battery voltage and check the 5 V reference wire. If the test lamp illuminates, the 5 V reference circuit is shorted to ground. Repair if necessary. If the test lamp does not illuminate, test the 5 V reference circuit for an open. Repair if necessary.

If there is no obvious problem and there is no 5 volt reference, the PCM may be faulty, however other codes are likely to be present. If 5 volts is present in the reference circuit, connect a 5 volt jumper wire to the EGR signal circuit. The scan tool EGR position should now read 100 percent. If it does not connect the test lamp to the battery voltage, check the signal circuit of the exhaust gas recirculation. If it is on, then the signal circuit is shorted to ground. Repair if necessary. If the indicator does not illuminate, check for an open in the EGR signal circuit. Repair if necessary.

If the scan tool displays a 5 percent EGR position after connecting the 100 V reference circuit to the EGR signal circuit, check for poor tension on the terminals on the EGR valve connector. If the wiring is OK, replace the EGR valve.

Associated EGR Codes: P0400, P0401, P0402, P0403, P0404, P0406, P0407, P0408, P0409

HOW DOES A MECHANIC DIAGNOSTIC CODE P0405?

• Scans codes and data freeze frame documents to confirm the problem
• Clear engine codes and road test to see if fears and codes return.
• Monitors the pid of the EGR sensor on the scanner to see if the sensor is indicating the valve is in the correct closed position or if the sensor voltage feedback is below specification.
• Removes the EGR sensor connector, inspects the connector for corrosion and cleans if necessary.
• Check the connector if the 5 volt reference reaches the sensor connector.
• Connect the sensor reference voltage and the feedback pins together and check the scanner to show the reference voltage at the EGR sensor pid sensor.
• Replaces the EGR sensor or repairs the wiring as needed, then double checks for correct system readings.

COMMON ERRORS WHEN DIAGNOSING CODE P0405

• Do not connect the sensor reference voltage and the feedback signal together to make sure all wiring is good before replacing the EGR position sensor.
• Failure to check the wiring and connection to the EGR position sensor for a short circuit or open circuit before replacing the EGR position sensor.

HOW SERIOUS CODE P0405 IS?

• The ECM can disable the EGR system and make it inoperable when this code is active.
• Illumination of the Check Engine light will result in an emission test failure.
• The position of the EGR is critical for the ECM to properly control the opening and closing of the EGR valve and can cause the engine to run rough and stall.

WHAT REPAIRS CAN FIX CODE P0405?

• Replace the EGR position sensor, making sure the wiring is good.
• Short Harness Attachment to EGR Position Sensor or Signal Return Connector
• Elimination of a break in the reference voltage to the EGR sensor

ADDITIONAL COMMENTS TO BE AWARE OF CODE P0405

Code P0405 is triggered when the EGR position is lower than the expected ECM sensor position and the most common cause is that the EGR sensor has an internal open circuit.

P0405 ✅ SYMPTOMS AND CORRECT SOLUTION ✅ - OBD2 Fault Code

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