Engine-Codes - Generic - P20EF

P20EF Code - SCR NOx Pre-Catalyst Efficiency Below Threshold Bank 1

- Code Popularity: 6,786 Views
- Repair Importance Level: 3/3
- Repair Difficulty Level: 3/3
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What are the Possible Causes of the DTC P20EF?

NOTE: The causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes.
  • Faulty NOx Sensor
  • Diesel Exhaust Fluid
  • Faulty Selective Catalyst Reduction (SCR) Catalyst
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How to Fix the DTC P20EF?

Check the 'Possible Causes' listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.

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What is the Cost to Diagnose the Code?

Labor: 1.0

The cost to diagnose the P20EF code is 1.0 hour of labor. The diagnosis time and labor rates at auto repair shops vary depending on the location, make and model of the vehicle, and even the engine type. Most auto repair shops charge between $75 and $150 per hour.

What are Code Possible Symptoms?

  • Engine Light ON (or Service Engine Soon Warning Light)

What Does the P20EF Code Mean?

The Selective Catalyst Reduction (SCR) catalyst is monitored to ensure it is capable of NOx conversion. The concentration of NOx upstream of the SCR is calculated based on a model. NOx concentration downstream of the SCR is measured with a NOx sensor. Using these concentrations, the cumulative efficiency of the SCR catalyst is calculated and compared to a threshold. If the cumulative efficiency is below this threshold for a sufficient period of time, a fault will be indicated.
The reductant, Diesel Exhaust Fluid (DEF), which is used as part of the SCR catalyst reaction, is monitored to ensure the tank is not refilled with an improper reductant. Upon detection of a refill event, the monitor is activated. After the SCR Catalyst Efficiency Monitor has completed and the SCR has been determined to be functional, the efficiency monitor continues to calculate the cumulative efficiency of the system. Each subsequent value for cumulative efficiency is included in two filtering routines, one for short term efficiency and the other for long term efficiency. If the difference between the two filtered efficiencies becomes greater than a threshold, a fault is indicated. the short term efficiency needs to be less than 0.20 and the delta between short and long term efficiency needs to be greater than 0.10.

P20EF Code - SCR NOx Pre-Catalyst Efficiency Below Threshold Bank 1

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Code P20EF Information for Specific Makes

  • P20EF Dodge SCR NOx Pre-Catalyst Efficiency Below Threshold Bank 1
  • P20EF Ford SCR NOx Pre-Catalyst Efficiency Below Threshold Bank 1

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