AutoCodes – BMW – P0620 BMW

P0620 BMW Code - Generator Control Circuit Malfunction

Quick Answer

The Engine Control Module (ECM) uses the generator turn on signal circuit to control the generator. Common causes include Battery charge, Faulty Generator, Generator harness is open or shorted. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means: P0620 BMW indicates Generator Control Circuit Malfunction.
Common causes: Common causes include Battery charge, Faulty Generator, Generator harness is open or shorted.
Severity: High - diagnose this code as soon as possible.
Can I drive?: Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

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Code Popularity 5,172

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on May 01, 2019

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P0620 BMW Description

The Engine Control Module (ECM) uses the generator turn on signal circuit to control the generator. A high side driver within the ECM allows the ECM to turn the generator ON and OFF. When Generator operation is desired, the ECM sends a 5 volt signal to the voltage regulator via the generator turn on signal circuit. This causes the voltage regulator to begin controlling the generator field circuit. Once the Generator is enabled by the ECM, the voltage regulator controls generator output independently of the ECM. Under certain operating conditions, the ECM can turn Off the generator by turning Off the 5 volt signal on the generator turn on signal circuit.

OBDII Code P0620 BMW - Generator Control Circuit Malfunction - AutoCodes.com — P0620 BMW Code - Generator Control Circuit Malfunction

What does this mean?

What are the Possible Causes of the DTC P0620 BMW?

Battery charge
Faulty Generator
Generator harness is open or shorted
Generator circuit poor electrical connection
Engine Control Module (ECM) controlled generator
Faulty ECM

How to Fix the DTC P0620 BMW?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0620 BMW code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

Need more information about the P0620 BMW code?

Need more information on how to fix the P0620 BMW code? Get Access to Factory Service Manuals

Need Help with the Code?

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About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about P0620 BMW Code

1. What does the OBDII code P0620 indicate on a BMW?

The P0620 code on a BMW indicates a malfunction in the generator control circuit, suggesting an issue with the vehicle's charging system, specifically related to the generator's (alternator's) ability to charge the battery.

2. What are common symptoms of code P0620 in a BMW?

Common symptoms include the battery warning light on the dashboard, dimming headlights, issues with electrical components, and the vehicle may experience difficulty starting or stalling.

3. What causes the code P0620 to be triggered on a BMW?

Causes may include a faulty alternator, poor battery condition, defective voltage regulator, wiring issues in the charging circuit, or a bad connection in the generator control circuit.

4. How can I diagnose the P0620 code in a BMW?

Diagnosis should start with a visual inspection of the alternator, battery, and associated wiring. Check for loose connections, corrosion, or damaged wires. A multimeter can be used to verify the output voltage of the alternator to ensure it matches BMW specifications.

5. What are the repair steps for fixing code P0620 on a BMW?

Repair may involve replacing the faulty alternator, securing loose connections, replacing damaged wires, or installing a new battery if it's unable to hold a charge. Resetting the code and conducting a test drive to ensure the issue is resolved is also necessary.

6. Can I drive my BMW with the code P0620 showing?

While you may be able to drive for a short distance, it is not advisable as the vehicle's charging system may fail, leading to a drained battery and potentially leaving you stranded. It's best to address the issue promptly.

7. Does code P0620 on a BMW affect fuel economy?

Indirectly, yes. If the charging system is malfunctioning, it can lead to poor battery performance and an overall strain on the electrical system, which might affect the fuel injection system and other fuel economy-related components.

8. How urgent is it to fix a P0620 code on a BMW?

It is fairly urgent to address this issue to avoid further complications, such as battery failure or damage to the electrical system, which can result in more significant vehicle malfunctions.

9. What tools are needed to verify the cause of a P0620 on a BMW?

A digital multimeter to check the alternator's output voltage, a diagnostic scanner to read and clear the OBDII codes, and basic hand tools to inspect and possibly replace components of the charging system are necessary.