P20E8 Code: Diesel Intake Air Flow Position Sensor Circuit Low

Is a P20E8 code showing up on your scanner tool? It can mean that your vehicle has one or more problems with its components. You’ll need to troubleshoot this diagnostic trouble code (DTC) as soon as possible to prevent further issues.

What Does the P20E8 Code Mean?

A P20E8 code or “Diesel Intake Air Flow Position Sensor Circuit Low” is a generic powertrain code that applies to diesel-powered vehicles with OBD-II. It can affect certain Chevy, Dodge, Ford and GMC trucks.

A vehicle’s powertrain control module (PCM) can store a P20E8 code if the electric signal from the diesel intake air flow position sensor (DIAFPS) doesn’t match normal engine operating conditions in the PCM’s memory. The DIAFPS converts the incoming airflow volume into a signal for the PCM to determine the amount of clean air entering the diesel engine versus the amount of exhaust entering the exhaust gas recirculation (EGR) system. If the PCM doesn’t detect a change in airflow, the DIAFPS or EGR system might be malfunctioning. The PCM also checks whether the voltage signal from the DIAFPS is below a set level (normally under 0.3 volts) and sets the code appropriately.

Note: The definition of code P20E8 might be different depending on the vehicle manufacturer. Consult the appropriate repair manual or repair database for the exact code definition.

What are the Common Causes of the P20E8 Code?

Some factors can lead to a P20E8 code. Here are a few of the P20E8 code’s most frequent causes.

• The signal circuit to the DIAFPS sensor is short or ground
• Malfunctioning DIAFPS Sensor
• Faulty PCM

What are the Common Symptoms of the P20E8 Code?

Your vehicle’s PCM can store multiple DTCs, such as P20E7 and P20E8. Make sure to check for other codes to rule out symptoms that aren’t listed here.  However, if your PCM only has a P20E8 stored, you can expect one or more of the following symptoms to manifest.

• Illuminated check engine light
• Stuck in low idle speed
• EGR system not working
• Soot build up doesn’t get burned off by the diesel particulate filter

How to Diagnose the P20E8 Code

The specific diagnostic steps will vary depending on your vehicle’s make, model, and powertrain configuration. The following video is a basic guide to diagnosing this code. However, the wire colors and DIAFPS type might be different for your vehicle. What might work to resolve a P02E8 code in a Duramax engine might be different for other engines. Make sure to consult your vehicle’s repair manual before attempting any diagnosis or repairs.

How to Fix the P20E8 Code

There’s no magic bullet for troubleshooting a P20E8 code or any DTC for that matter. You’ll need to find the underlying causes of this code to figure out the right fix. You can check out OBD-II resources online for reference. We recommend searching for technical service bulletins related to your vehicle’s problem to save time on research. You can also get an ALLDATA single-vehicle subscription for more detailed information on your vehicle.

Troubleshooting DTCs isn’t exactly a walk in the park. If you don’t have the required skills and knowledge to address a P20E8 code, you might want to leave the repairs to a professional mechanic.