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Engine-Codes – RAM – P0408 RAM

P0408 RAM Code - Exhaust Gas Recirculation Sensor 'B' Circuit High

Quick Answer

The P0408 diagnostic trouble code (DTC) specifically refers to a fault in the Exhaust Gas Recirculation (EGR) sensor 'B' circuit being detected as too high. Common causes include Faulty EGR sensor 'B', Wiring or electrical issues in the EGR sensor circuit, ECM malfunction. 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 RAM indicates Exhaust Gas Recirculation Sensor 'B' Circuit High.
Common causes
Common causes include Faulty EGR sensor 'B', Wiring or electrical issues in the EGR sensor circuit, ECM malfunction.
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.
What is this?
Table of contents Created and updated by William Orellana on Sep 12, 2024
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Code P0408 RAM Description

The P0408 diagnostic trouble code (DTC) specifically refers to a fault in the Exhaust Gas Recirculation (EGR) sensor 'B' circuit being detected as too high. The EGR system in a vehicle is responsible for recirculating a portion of the engine's exhaust gases back into the intake manifold to reduce combustion temperatures and emissions of nitrogen oxides (NOx). The EGR sensor 'B' is crucial for monitoring the EGR system's operation and ensuring that the correct amount of exhaust gas is being recirculated.

OBDII Code P0408 RAM - Exhaust Gas Recirculation Sensor 'B' Circuit High
P0408 RAM Code - Exhaust Gas Recirculation Sensor 'B' Circuit High

Common Causes of P0408 RAM

  1. Faulty EGR sensor 'B'.
  2. Wiring or electrical issues in the EGR sensor circuit.
  3. ECM malfunction.
  4. Carbon buildup in the EGR system.
  5. Vacuum leak in the EGR system.

Symptoms of P0408 RAM

  1. Check Engine Light (CEL) illuminated on the dashboard.
  2. Reduced fuel efficiency.
  3. Rough idling or stalling.
  4. Increased emissions during vehicle inspection.
  5. Engine knocking or pinging noises.

How to Fix P0408 RAM

  1. Begin by diagnosing the specific cause of the high voltage signal in the EGR sensor 'B' circuit using a diagnostic scanner.
  2. Inspect the EGR sensor 'B' and its wiring for any visible damage or corrosion. Replace the sensor if necessary.
  3. Check and clean the EGR valve and passages for any carbon buildup that could be affecting its operation.
  4. Test the ECM to ensure it is functioning properly and communicating with the EGR system correctly.
  5. Clear the DTC and reset the ECM to see if the issue has been resolved after repairs.

Cost to Fix P0408 RAM

The typical repair costs for addressing the P0408 code can range from $150 to $400, depending on the specific cause of the issue and the cost of parts and labor. It's important to note that diagnostic time and labor rates at auto repair shops can vary, so it's advisable to check with local shops for a more precise estimate based on your vehicle make and model. Additionally, rates may be higher at dealerships or in metropolitan areas, while independent shops may offer more affordable options.

When is the Code Detected?

An improper voltage signal is sent to ECM through the valve

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About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about P0408 RAM Code

1. What are the common symptoms of OBDII code P0408?

The common symptoms of code P0408 include rough idling, decreased fuel efficiency, engine stalling, and the illumination of the Check Engine Light.

2. What does the OBDII code P0408 indicate?

OBDII code P0408 indicates a problem with the Exhaust Gas Recirculation (EGR) Sensor 'B' Circuit High. This means that the voltage signal from the EGR sensor is higher than the expected range.

3. What are the possible causes of OBDII code P0408?

Possible causes of code P0408 include a faulty EGR sensor, damaged wiring or connectors in the EGR circuit, a malfunctioning EGR valve, or issues with the vehicle's Engine Control Module (ECM).

4. How can I diagnose the cause of OBDII code P0408?

Diagnosing code P0408 usually involves using a scan tool to retrieve the code, checking the EGR sensor's voltage output, inspecting the EGR valve and related components for damage, and testing the wiring and connectors for continuity.

5. Can I still drive my vehicle with OBDII code P0408?

It is not recommended to drive your vehicle with OBDII code P0408 unresolved, as it can lead to further damage to the engine and emissions system. It is best to address the issue promptly.

6. How can I repair OBDII code P0408?

Repairing code P0408 may involve replacing the EGR sensor, repairing or replacing damaged wiring or connectors, cleaning or replacing the EGR valve, or addressing any underlying issues with the ECM.

7. Can a DIY enthusiast fix OBDII code P0408?

Depending on your skill level and access to tools, a DIY enthusiast may be able to address OBDII code P0408 by following diagnostic procedures, replacing components, and clearing the code with a scan tool.

8. Will resetting the Check Engine Light resolve OBDII code P0408?

Simply resetting the Check Engine Light without addressing the underlying issue causing code P0408 will not resolve the problem. It is important to diagnose and repair the root cause of the code.

9. How long does it typically take to repair OBDII code P0408?

The time it takes to repair code P0408 can vary depending on the exact cause of the issue, the availability of parts, and the skill level of the person performing the repairs. It may range from a few hours to a day.

10. What happens if OBDII code P0408 is ignored?

Ignoring OBDII code P0408 can lead to poor engine performance, decreased fuel efficiency, increased emissions, and potential damage to other engine components over time. It is advisable to address the issue promptly.

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