AutoCodes – GMC – B0503 GMC

B0503 GMC Code - Short To Voltage Or BCM Open Internally In The RH DRL Relay Control Circuit

Quick Answer

The Body Control Module (BCM) provides control for the Right Daylight Running Lamp (DRL) relay circuit. Common causes include Faulty Right Daylight Running Lamp (DRL) Relay, Right Daylight Running Lamp (DRL) Relay harness is open or shorted, Right Daylight Running Lamp (DRL) Relay circuit poor electrical connection. Severity is Low - monitor the vehicle and repair when practical. The vehicle can usually be driven if no severe symptoms are present, but symptoms should be checked before extended driving.

What it means: B0503 GMC indicates Short To Voltage Or BCM Open Internally In The RH DRL Relay Control Circuit.
Common causes: Common causes include Faulty Right Daylight Running Lamp (DRL) Relay, Right Daylight Running Lamp (DRL) Relay harness is open or shorted, Right Daylight Running Lamp (DRL) Relay circuit poor electrical connection.
Severity: Low - monitor the vehicle and repair when practical.
Can I drive?: The vehicle can usually be driven if no severe symptoms are present, but symptoms should be checked before extended driving.

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Code Popularity 833

How popular is this code, among other codes? Low

Repair Importance Level

Low (Monitor) (1 / 3)

Repair Difficulty Level

Intermediate (2 / 3)

What is this?

Table of contents Created and updated by William Orellana on Mar 11, 2021

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code B0503 GMC Description

The Body Control Module (BCM) provides control for the Right Daylight Running Lamp (DRL) relay circuit. The BCM grounds the RH DRL relay control circuit in order to energize the RH DRL relay and turn ON the RF turn signal. This allows the RF turn signal to be used for DRL and approach lighting functions. The BCM monitors the voltage level on the RH DRL relay control circuit. When the BCM commands the relay ON, the voltage level on the RH DRL relay control circuit should be low. When the relay is OFF, the voltage on the RH DRL relay control circuit should be high. If the BCM detects a voltage level other than expected, a malfunction is present and a Diagnostic Trouble Code (DTC) will set.

OBDII Code B0503 GMC - Short To Voltage Or BCM Open Internally In The RH DRL Relay Control Circuit - AutoCodes.com — B0503 GMC Code - Short To Voltage Or BCM Open Internally In The RH DRL Relay Control Circuit

What does this mean?

What are the Possible Causes of the DTC B0503 GMC?

Faulty Right Daylight Running Lamp (DRL) Relay
Right Daylight Running Lamp (DRL) Relay harness is open or shorted
Right Daylight Running Lamp (DRL) Relay circuit poor electrical connection
Faulty Body Control Module (BCM)

How to Fix the DTC B0503 GMC?

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 B0503 GMC 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.

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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 B0503 GMC Code

1. What are the common symptoms of OBDII code B0503 GMC?

- Common symptoms include the right headlight not working, flickering or dimming of the right headlight, or the right daytime running light (DRL) not functioning properly.

2. What does the OBDII code B0503 GMC indicate?

- This code indicates a short to voltage or an open internally in the right headlight relay control circuit within the Body Control Module (BCM).

3. What are the possible causes of OBDII code B0503 GMC?

- Possible causes include a faulty right headlight relay, a wiring issue in the circuit, a malfunctioning BCM, or a poor electrical connection in the circuit.

4. How can I diagnose the root cause of OBDII code B0503 GMC?

- Diagnose by inspecting the wiring for any visible damage, testing the right headlight relay, checking the BCM for proper functioning, and ensuring all electrical connections are secure.

5. Can OBDII code B0503 GMC be repaired at home?

- Depending on the cause, some repairs like checking and securing connections or replacing a faulty relay can be done at home. However, complex issues may require professional diagnosis and repair.

6. Is it safe to drive with OBDII code B0503 GMC present?

- It is not recommended to drive with this code present, as it can affect the proper functioning of the right headlight or DRL, compromising visibility and safety on the road.

7. How much does it typically cost to repair OBDII code B0503 GMC?

- The cost of repair can vary based on the specific cause of the issue. Simple fixes like replacing a relay may cost less, while more complex issues involving the BCM or wiring could be more expensive.

8. Can resetting the OBDII code B0503 GMC resolve the issue temporarily?

- Resetting the code may temporarily turn off the warning light, but it will not fix the underlying problem causing the code to trigger. It is important to diagnose and address the root cause.

9. Will OBDII code B0503 GMC cause my vehicle to fail an emissions test?

- This code is related to the right headlight circuit and should not directly impact emissions. However, it is still important to address the issue for proper vehicle operation.

10. How can I prevent OBDII code B0503 GMC from recurring in the future?

- Regularly inspecting and maintaining the electrical components related to the right headlight circuit, ensuring proper connections, and addressing any issues promptly can help prevent this code from recurring.