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AutoCodes - Generic - P04A1

P04A1 Code - Exhaust Pressure Control Valve 'B' Low

- Code Popularity: 1,708 Views
- Repair Importance Level: 3/3
- Repair Difficulty Level: 3/3
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What are the Possible Causes of the DTC P04A1?

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 P04A1?

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.

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What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P04A1 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.

What are Code Possible Symptoms?

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

Code P04A1 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 P04A1 - Exhaust Pressure Control Valve 'B' Low - AutoCodes.com
P04A1 Code - Exhaust Pressure Control Valve 'B' Low

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Code P04A1 comments

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