Generator Control Circuit Malfunction


Table of contents

P0620 MERCEDES-BENZ Possible Causes

  • Battery charge
  • Faulty Alternator
  • Alternator harness is open or shorted
  • Alternator circuit poor electrical connection
  • Faulty Engine Control Module (ECM)

How do I fix code P0620 MERCEDES-BENZ?

  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’s pins.

Tech Notes

  • Mercedes Benz Code = 0365 Operational fault of component (generator) (P0620)

Cost of diagnosing the P0620 MERCEDES-BENZ code

  The cost of diagnosing the P0620 MERCEDES-BENZ code is 1.0 hour of labor. The auto repair labor rates vary by location, your vehicle’s make and model, and even your engine type. Most auto repairs shops charge between $75 and $150 per hour.

When is the code detected

  The Engine Control Module (ECM) has fault detection circuitry which monitors the state of the generator turn on signal circuit. If the fault detection circuit senses a voltage other than what is expected, this P0620 code will set. The voltage regulator also contains fault detection circuitry. If the regulator detects a problem, the regulator will ground the generator turn on signal circuit, pulling the voltage low. This also causes the ECM to set the P0620 code.

Possible Symptoms

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

P0620 MERCEDES-BENZ Description

  This fault code is stored in a control module when the charging system control does not perform as expected. In order to create a more efficient charging system manufacturers are now using an intelligent charging system. A control module sends a signal to the alternator depending on engine load and operating conditions. This signal is responsible for altering the alternator field current. Manufacturers can use a varying PWM, or pulse width modulation, to command and receive feedback from the alternator. A larger current flow through the field winding will result in a higher charging output voltage. A reduced current flow through the field winding will result in a lower charging output voltage. Some manufacturers now use LIN, or local inter-connection network, communication to control the alternator output voltage. Both LIN bus and PWM control can be tested using an oscilloscope. Some vehicle manufacturers offer a tool which can be used to control the alternator disconnected for the control module which is responsible for controlling it. This allows for accurate diagnosis.

Related Codes

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