P0408 Code - Exhaust Gas Recirculation Sensor 'B' Circuit High
Quick Answer
Early Exhaust Gas Recirculation (EGR) systems components include an EGR Valve, an Engine Control Module (ECΜ) Controlled Vacuum Switch Valve or EGR Solenoid, and an EGR Vacuum Modulator. Common causes include Faulty EGR volume control solenoid valve, Carbon built up on EGR valve, EGR volume control solenoid valve harness is open or shorted. Severity is Moderate - service should be scheduled soon. The vehicle may still be drivable for short trips if it runs normally, but avoid hard driving and repair it soon.
- What it means
- P0408 indicates Exhaust Gas Recirculation Sensor 'B' Circuit High.
- Common causes
- Common causes include Faulty EGR volume control solenoid valve, Carbon built up on EGR valve, EGR volume control solenoid valve harness is open or shorted.
- Severity
- Moderate - service should be scheduled soon.
- Can I drive?
- The vehicle may still be drivable for short trips if it runs normally, but avoid hard driving and repair it soon.
Code P0408 Description
The EGR system on recently built vehicles uses a step motor to control the flow rate of EGR from the exhaust manifold. This motor has four winding phases. It operates according to the output pulse signal of the ECΜ. Two windings are turned ON and OFF in sequence. Each time an ON pulse is issued, the valve opens or closes, changing the flow rate. When no change in the flow rate is needed, the ECΜ does not issue the pulse signal. Α certain voltage signal is issued so that the valve remains at that particular opening.
What are the Possible Causes of the DTC P0408?
- Faulty EGR volume control solenoid valve
- Carbon built up on EGR valve
- EGR volume control solenoid valve harness is open or shorted
- EGR volume control solenoid valve circuit poor electrical connection
- Faulty EGR temperature sensor and circuit
How to Fix the DTC P0408?
Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.
What is the Cost to Diagnose the Code?
Labor: 1.0
To diagnose the P0408 code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.
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Information for Specific Makes
- P0408 Audi — Exhaust Gas Recirculation Sensor 'B' Circuit High
- P0408 Chrysler — Exhaust Gas Recirculation Sensor 'B' Circuit High
- P0408 Dodge — Exhaust Gas Recirculation Sensor 'B' Circuit High
- P0408 Jeep — Exhaust Gas Recirculation Sensor 'B' Circuit High
- P0408 Mercedes-Benz — Exhaust Gas Recirculation Sensor 'B' Circuit High
- P0408 RAM — Exhaust Gas Recirculation Sensor 'B' Circuit High
- P0408 Volkswagen — Exhaust Gas Recirculation Sensor 'B' Circuit High
Frequently Asked Questions about P0408 Code
1. What are the common symptoms of OBDII code P0408?
- Common symptoms of P0408 may include engine stalling, rough idle, decreased fuel efficiency, and the illumination of the Check Engine Light.
2. What can cause the Exhaust Gas Recirculation (EGR) Sensor 'B' Circuit High fault code?
- The P0408 code is typically triggered by a faulty EGR position sensor, damaged wiring or connectors, or a malfunctioning EGR valve.
3. How can I diagnose the cause of P0408?
- To diagnose P0408, you can use an OBDII scanner to retrieve the fault code and then visually inspect the EGR system components for damage or corrosion. Testing the EGR sensor and related wiring may also be necessary.
4. Can a dirty EGR valve cause code P0408?
- Yes, a dirty or clogged EGR valve can disrupt the sensor readings and lead to the P0408 code being triggered. Regular maintenance can help prevent this issue.
5. What are the repair options for OBDII code P0408?
- Repair options for P0408 may include cleaning or replacing the EGR valve, testing and replacing the EGR sensor, repairing damaged wiring or connectors, and resetting the fault code with a scanner.
6. Will driving with code P0408 harm my vehicle?
- Driving with code P0408 may result in decreased engine performance and fuel efficiency. Continued driving with this fault unresolved can potentially cause damage to other engine components over time.
7. How urgent is it to address code P0408?
- While P0408 may not cause immediate harm to your vehicle, it is recommended to address the issue promptly to prevent further engine problems and ensure optimal performance.
8. Can I reset the Check Engine Light after fixing code P0408?
- Yes, once you have addressed the underlying cause of P0408, you can reset the Check Engine Light using an OBDII scanner to clear the fault code.
9. Is it possible to prevent OBDII code P0408 from recurring?
- Regular maintenance of the EGR system, including cleaning or replacing components as needed, can help prevent the recurrence of P0408. Keeping the system in good condition is key to avoiding this fault code.
10. Should I attempt to repair OBDII code P0408 myself?
- If you have experience with automotive repair and access to the necessary tools, you may be able to address P0408 yourself. However, if you are unsure or uncomfortable with the process, it is advisable to seek professional assistance to ensure the issue is properly diagnosed and resolved.
Discuss the causes and fixes for P0408 OBDII Code
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i have a 2004 f150 with a 4.2 with codes for missfire on #5 and #3 cyl and p0408 iv changed the coil , plugs and plug wires nothing has changed, it only misses somtimes usually around accelaration of about 2000 rpms and ltft for bank 2 is very high 23.99 , im going to check for vaccume leaks . any advice would help thanks . wally
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The P0408 code is for the EGR system. If the EGR got stuck open, it can cause an engine misfire.
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hello on VW 1.6tdi 2010 first the p046c00 fault code come up.
I cleaned the egr complete and replaced the vacum regulator because it was not working. for 10km the car was working fine.After that the fault code p04800 always comes up and the car goes in limp mode...what could this be?
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