Engine-Codes - Mercedes-benz - P0175 MERCEDES-BENZ

P0175 MERCEDES-BENZ - System Too Rich Bank 2

Repair Importance Level: 3/3
Repair Difficulty Level: 3/3  What is this?
Table of contents

P0175 MERCEDES-BENZ Possible Causes

  • Faulty front heated oxygen sensor
  • Ignition misfiring
  • Faulty fuel injectors
  • Exhaust gas leaks
  • Incorrect fuel pressure
  • Faulty Mass Air Flow (MAF) sensor

How is the P0175 MERCEDES-BENZ code repair?

Start by checking 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's pins.

Tech Notes

Mercedes Benz Code = 0342 Self-adaptation of mixture formation for enrichment at partial load for the left cylinder bank is below the permissible limit. (P0175)

What is the cost to diagnose the P0175 MERCEDES-BENZ code

Labor: 1.0

The cost to diagnose the P0175 MERCEDES-BENZ code is 1.0 hour of labor. The auto repair's diagnosis time and labor rates vary by location, vehicle's make and model, and even your engine type. Most auto repair shops charge between $75 and $150 per hour.
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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.)

Possible Symptoms

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


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.

More Information

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