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P0172 Mercedes-Benz Code - System Too Rich Bank 1

- Code Popularity: 85,808 Views
- Repair Importance Level: 3/3
- Repair Difficulty Level: 3/3
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What are the Possible Causes of the DTC P0172 Mercedes-Benz?

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 Front Heated Oxygen Sensor
  • Faulty Spark Plugs
  • Faulty Mass Air Flow (MAF) sensor
  • Exhaust Gas Leaks
  • Ignition Misfiring
  • Incorrect Fuel Pressure
  • Faulty Fuel Injectors
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How to Fix the DTC P0172 Mercedes-Benz?

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

Mercedes Benz Code = 0338 Self-adaptation of mixture formation for enrichment at partial load for the right cylinder bank is below the permissible limit. (P0172)

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What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0172 Mercedes-Benz 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?

- Fuel injection system does not operate properly.
- The amount of mixture ratio compensation is too large. (The mixture ratio is too rich.)

What are Code Possible Symptoms?

  • Engine Light ON (or Service Engine Soon Warning Light)
  • Excessive Fuel Consumption

Code P0172 Mercedes-Benz Description

This fault code is stored in the Engine Control Module (ECM) when the ECM is no longer capable of controlling the air fuel ratio. For correct operation of the catalytic converter the ECM is required to keep the air fuel ratio (AFR) at approximately lambda 1, this equates to an AFR of 14.7:1 by mass. This is achieved by trimming the fuel mixture to the required amount to cater for slight anomalies during normal operating conditions. However when a fault causes the fuel trim to exceed a predetermined level the malfunction indication light is illuminated and a limited operating strategy is employed. The pre-catalyst exhaust gas oxygen sensor is the primary component used for calculating the fuel trim once the system enters closed loop control. The fuel trim data can be displayed as a percentage, either positive or negative.
Under this condition the fuel trim data will display a negative value. The ECM will decrease the injection duration to counteract the excessively rich mixture. This fault can be stored due to a faulty coolant temperature sensor, excessively high fuel pressure or a faulty fuel injector.
The fuel trim is monitored under various loads and conditions. If a load or condition is included in the fault code this can be an advantage during diagnosis. Normally a code set during idle or light load is relating to an air leak. And a code set during high or part load can be a fuelling issue or an erroneous sensor signal.

OBDII Code P0172 Mercedes-Benz - System Too Rich Bank 1 - AutoCodes.com
P0172 Mercedes-Benz Code - System Too Rich Bank 1

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