Engine-Codes - Generic - P2178

P2178 Code - System Too Rich Off Idle Bank 1

- Code Popularity: 57,361 Views
- Repair Importance Level: 3/3
- Repair Difficulty Level: 2/3
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What are the Possible Causes of the DTC P2178?

NOTE: The causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes.
  • Intake air leaks
  • Faulty Front Heated Oxygen Sensor (HO2S)
  • Ignition misfiring
  • Faulty fuel injectors
  • Incorrect fuel pressure
  • Faulty Mass Air Flow (MAF) sensor
  • Incorrect Positive Crankcase Ventilation (PCV) hose connection

Code Tech Notes

The engine is "too rich" when the O2 sensors detect more fuel than air during combustion. Leaking fuel injectors (stuck open or damaged seals) and faulty Mass Air Flow (MAS) sensors are the most likely causes of this problem.

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How to Fix the DTC P2178?

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 P2178 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 P2178 Code Mean?

With the Air/Fuel Mixture Ratio Self-Learning Control, the actual mixture ratio can be brought closer to the theoretical mixture ratio based on the mixture ratio feedback signal from the heated oxygen sensors 1. The Engine Control Module (ECM) calculates the necessary compensation to correct the offset between the actual and the theoretical ratios.
In case the amount of the compensation value is extremely small (The actual mixture ratio is too rich.), the ECM judges the condition as the fuel injection system malfunctions and lights up the MIL (2 trip detection logic).

P2178 Code - System Too Rich Off Idle Bank 1

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Code P2178 Information for Specific Makes

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