B1820 – Wiper Rear Motor Up Relay Coil Circuit Short To Battery

The ODBII code B1820 indicates a short circuit in the rear wiper motor up relay coil circuit, meaning that the circuit is receiving power directly from the battery instead of being controlled properly by the relay.

The severity of ODBII code B1820 is moderate.

Common Causes For: B1819 Wiper Rear Motor Up Relay Coil Circuit Open

• Shorted wiring or connectors
• Faulty rear wiper motor
• Defective relay
• Corroded or damaged terminals
• Malfunctioning switch
• Grounding issues

Common misdiagnosis for B1820 Wiper Rear Motor Up Relay Coil Circuit Short To Battery

• Faulty rear wiper motor
• Defective wiper switch
• Wiring issues or shorts in the harness
• Malfunctioning body control module (BCM)
• Incorrectly installed or damaged relay
• Grounding issues
• Faulty fuse or circuit breaker

Common Troubleshooting Steps

The OBD-II code B1820 indicates a problem with the rear wiper motor up relay coil circuit, specifically a short to battery. Here are some common troubleshooting steps to diagnose and resolve this issue:

• Visual Inspection:
• Check the wiring and connectors associated with the rear wiper motor and relay for any signs of damage, corrosion, or loose connections.
• Inspect the relay itself for any physical damage.
• Check the Relay:
• Test the rear wiper motor relay by swapping it with a similar relay in the fuse box (if applicable) to see if the problem persists.
• If you have a multimeter, you can also test the relay for continuity and proper operation.
• Inspect the Wiper Motor:
• Disconnect the rear wiper motor and check for any signs of damage or short circuits.
• Measure the resistance of the motor windings to ensure they are within specifications.
• Check for Shorts:
• Use a multimeter to check for continuity between the relay coil circuit and the battery. A short circuit will show continuity where there shouldn’t be any.
• Inspect the wiring harness for any pinched or frayed wires that could be causing a short.
• Test the Circuit:
• With the ignition on, use a multimeter to check for voltage at the relay and the wiper motor. Ensure that the voltage is within the expected range.
• If there is no voltage, trace the circuit back to the power source to identify any breaks or issues.
• Check Ground Connections:
• Ensure that the ground connections for the rear wiper motor and relay are clean and secure. A poor ground can cause erratic behavior.
• Scan for Additional Codes:
• Use an OBD-II scanner to check for any other related trouble codes that may provide additional context for the issue.
• Consult Wiring Diagrams:
• Refer to the vehicle’s service manual for wiring diagrams to understand the circuit layout and identify any potential issues.
• Replace Faulty Components:
• If any faulty components are identified (such as the relay, wiper motor, or wiring), replace them as necessary.
• Clear Codes and Test Drive:
• After making repairs, clear the trouble codes using an OBD-II scanner and take the vehicle for a test drive to see if the code returns. If the issue persists after following these steps, it may be advisable to consult a professional mechanic for further diagnosis.