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P0479 Code - Exhaust Pressure Control Valve Intermittent

- Code Popularity: 8,242 Views
- Repair Importance Level: 2/3
- Repair Difficulty Level: 3/3
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What are the Possible Causes of the DTC P0479?

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 Exhaust Back Pressure Valve
  • Exhaust Back Pressure Valve harness is open or shorted
  • Exhaust Back Pressure Valve circuit poor electrical connection
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How to Fix the DTC P0479?

Review the 'Possible Causes' mentioned above and visually examine the corresponding wiring harness and connectors. Ensure to check for any damaged components and inspect the connector pins for signs of being broken, bent, pushed out, or corroded.

Code Tech Notes

Check the Exhaust Back Pressure Valve (EBPV) butterfly valve is opening and closing freely and not sticking. If it seems to move freely you can then check the connector and circuit for the EBPV solenoid.

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What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0479 code, it typically requires 1.0 hour of labor. The specific diagnosis time and labor rates at auto repair shops can differ based on factors such as the location, make and model of the vehicle, and even the engine type. It is common for most auto repair shops to charge between $75 and $150 per hour.

When is the Code Detected?

Problems with either the Exhaust Back Pressure (EBP) Device or the tube between the exhaust manifold and the EBP sensor can be detected during the exhaust back pressure step test, in which the Engine Control Module (ECM) commands and then measures a specific preprogrammed pressure and then measures time for pressure decay during the engine running test.

If the ECM detects an Exhaust Back Pressure (EBP), Engine Oil Temperature (EOT) or Intake Air Temperature (IAT) sensor fault it will disable the exhaust back pressure regulator.

What are Code Possible Symptoms?

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

Code P0479 Description

Exhaust Back Pressure Regulator - Is a variable position valve that controls exhaust back pressure during cold ambient temperatures to increase cab heat and decrease the amount of time needed to defrost the windshield. The Engine Control Module (ECM) uses the measured exhaust back pressure, (ambient) intake air temperature, engine oil temperature and engine load to determine the desired exhaust back pressure. Valve position is controlled by switching the output signal circuit to 12 volts inside the ECM. On/off time is modulated from 0 to 99 % dependent upon the exhaust back pressure desired.
Upon each initial engine start-up, the ECM exercises the exhaust back pressure valve by commanding it to cycle on and off once. If upon start-up the temperature of intake air sensed by the Intake Air Temperature (IAT) sensor is < 37°F (5°C) and the oil temperature sensed by the Engine Oil Temperature (EOT) sensor is between 32°-140°F (0-60°C) it will continue to keep the back pressure valve partially closed. As the oil temperature rises during engine operation, the ECM will control the valve in response to the rising oil temperature.

OBDII Code P0479 - Exhaust Pressure Control Valve Intermittent - AutoCodes.com
P0479 Code - Exhaust Pressure Control Valve Intermittent

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