P0408 - OBD Trouble Code

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The error code P0408 would start appearing when the PCM would detect an issue with the EGR (exhaust gas recirculation) system. If there would be a number of instances like this which are totally against the manufacturer’s specifications, then this fault code would be stored and it would result in the illumination of the check engine light.

The fault code P0408 can be defined as Exhaust Gas Recirculation Sensor B Circuit High.

There are there parts of the EGR system: EGR valve, DPFE (differential pressure sensor EGR) and actuator solenoid. This trouble code is generic, which would mean that it can apply to all the vehicles which are equipped with the OBD-II or the vehicles which are made since 1996 up to the present. The specifications on the definition, the troubleshooting steps as well as repairs can always vary from one vehicle make to another.

What causes this problem with the Exhaust Gas Recirculation Sensor B Circuit High?

• Faults in the EGR temperature sensor
• There can be some defects in the EGR temperature sensor circuit
• The EGR volume control solenoid valve circuit might have a shorted or open connection
• Issue of excessive carbon build-up on the EGR valve
• Flaws in the EGR volume control solenoid valve
• An open ground circuit for the EGR sensor
• The solenoid or EGR sensor might have internal failure

1. Air Intake temperature Sensor - Defective Air Intake temperature Sensor can be a major reason why P0408 code depicts. So, make sure to replace it online so that you don’t have to face any further issues.
2. Crankshaft Position Sensor - Everything is okay with the Air Intake temperature Sensor and still OBD code P0408 triggering? Then there must be some defects in Crankshaft Position Sensor. Replace them as soon as possible.
3. Powertrain Control Module - P0408 code flashing? Get your Powertrain Control Module inspected from a mechanic.
4. Fuel Pressure Regulator - If everything is alright with PCM, then there is surely some defect in Fuel Pressure Regulator. Get it replaced before the situation gets worse.
5. EGR Valve Gasket - P0408 code can display due to some issues in the EGR Valve Gasket. So, it is very important to replace the auto leaks with us at equitable prices.
6. Engine Coolant Temperature Sensor - Do you remember when was the last time you got your car Engine Coolant Temperature Sensor checked up? A dirty Engine Coolant Temperature Sensor can cause a lot of issues like displaying P0408 code.
7. Engine Control Module - Are there some faults in your Engine Control Module? Don’t waste time and get them replaced or else P0408 code can turn up.

You might be thinking that how would you diagnose these problems? We at Parts Avatar Canada would help you diagnose the major symptoms easily.

Common Symptoms

• Rise in the combustion temperatures and NOx emissions
• Appearance of the malfunction indicator lamp
• There can be possible surging while driving
• Issue of intermittent stall

The repairs which you will have to do to correct this fault code are simply straightforward; you can surely pinpoint the necessary repairs on the basis of your diagnosis. Have a look at some common fixes:

• Replace or repair the damaged EGR temperature sensor
• The faulty wiring or connectors for the EGR sensor circuit should be repaired or replaced
• Carefully clean out carbon build-up in the EGR valve
• The EGR volume control solenoid valve should be replaced or repaired

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Here are some steps which you should follow in order to diagnose this fault code:

A mechanic can diagnose a P0408 code by using an OBD-II scanner to identify it and any other codes which have been stored by the powertrain control module

Then, if the vehicle stalls after starting or might not run consistently, they will generally unplug the EGR valve before clearing the code and then restarting the vehicle. If the code appears again, they’ll then remove the EGR valve and clean out any built-up debris before reinstalling it and starting the vehicle again

If the problem still isn’t solved, they will block the EGR port and then he should try to crank the engine. If this seems to solve the problem, then the cause of the code is most likely a faulty EGR valve, which is stuck in the open position. Replacing it should resolve the code and allow the engine to start consistently. If the EGR valve is vacuum controlled, and unplugging it works to allow the vehicle to start and run, then there is some default in the EGR solenoid

If this is not the case, the mechanic will continue taking steps to diagnose the problem, including visual inspections of all wiring, circuits, and connections. After each test and repair is done, the mechanic will clear the code and retest it to ensure that it does not appear again

Common Mistakes When Diagnosing The P0408 Code

• It is a big mistake to directly replace the EGR valve assuming it to be defective
• If you will replace it directly without actually inspecting the real issues would result in spending unnecessary time and money