B1303 – Accessory Delay Relay Coil Circuit Open

The ODBII code B1303 indicates that there is an open circuit in the accessory delay relay coil, which may prevent the accessory delay function from operating properly.

The severity of ODBII code B1303 is generally considered moderate.

Common Causes For: B1302 Accessory Delay Relay Coil Circuit Failure

• Faulty accessory delay relay
• Open circuit in the relay coil wiring
• Corroded or loose connectors
• Faulty ignition switch
• Malfunctioning body control module (BCM)
• Blown fuse in the accessory delay circuit
• Short circuit in the wiring harness

Common misdiagnosis for B1303 Accessory Delay Relay Coil Circuit Open

• Faulty battery
• Bad ignition switch
• Defective body control module (BCM)
• Wiring issues or shorts
• Malfunctioning accessory delay relay
• Faulty fuses
• Issues with the power distribution center (PDC)

Common Troubleshooting Steps

The OBD-II code B1303 indicates an issue with the accessory delay relay coil circuit, specifically that the circuit is open. This can affect the operation of various electrical components in the vehicle, such as the radio, interior lights, and other accessories that are supposed to remain powered for a short time after the ignition is turned off. Here are some common troubleshooting steps to diagnose and resolve the B1303 code:

• Check for Additional Codes: Use an OBD-II scanner to check for any other trouble codes that may be present. This can provide additional context for the issue.
• Inspect the Wiring and Connectors: Visually inspect the wiring and connectors associated with the accessory delay relay. Look for signs of damage, corrosion, or loose connections.
• Pay special attention to the wiring harness that connects to the relay and any connectors that may be involved in the circuit.
• Test the Accessory Delay Relay: Locate the accessory delay relay in the fuse box or relay panel.
• Remove the relay and test it using a multimeter to check for continuity. If the relay is faulty, replace it with a new one.
• Check the Relay Circuit: With the relay removed, use a multimeter to check for voltage at the relay socket. You should see battery voltage on the appropriate terminals when the ignition is in the “ON” position.
• If there is no voltage, trace the wiring back to the power source and check for any breaks or shorts.
• Inspect the Ground Connection: Ensure that the ground connection for the accessory delay relay is secure and free of corrosion. A poor ground can cause the circuit to be open.
• Check for Short Circuits: Inspect the wiring for any signs of short circuits to ground or to other circuits. This can cause the relay to not function properly.
• Test the Control Circuit: If applicable, check the control circuit that activates the relay. This may involve testing switches or modules that control the relay operation.
• Clear the Codes and Test Drive: After performing the necessary repairs, clear the trouble codes using the OBD-II scanner and take the vehicle for a test drive to see if the code returns.
• Consult the Service Manual: If the issue persists, consult the vehicle’s service manual for specific diagnostic procedures related to the accessory delay relay circuit.
• Seek Professional Help: If you are unable to resolve the issue after following these steps, it may be best to consult a professional mechanic or technician who has experience with your specific vehicle make and model. By following these troubleshooting steps, you should be able to identify and resolve the issue related to the B1303 code.