B1821 – OBD-II DTC

OBD-II DTC B1821 – Wiper Rear Motor Up Relay Coil Circuit Short To Ground

DTC B1821 meaning

DTC B1821 refers to a diagnostic trouble code indicating a problem with the rear wiper motor up relay coil circuit. Specifically, it signifies that there is a short to ground in the circuit, which can prevent the rear wiper from functioning properly. This code is part of the On-Board Diagnostics II (OBD-II) system used in vehicles to monitor various components and systems.

DTC B1821 symptoms

Common symptoms associated with DTC B1821 may include:

• Rear wiper motor not operating
• Intermittent or erratic operation of the rear wiper
• Inability to activate the rear wiper through the control switch
• Dashboard warning lights related to the wiper system

DTC B1821 causes

Several factors can lead to the occurrence of DTC B1821, including:

• Short circuit in the wiring harness
• Faulty rear wiper motor
• Defective relay or relay socket
• Corroded or damaged connectors
• Issues with the vehicle’s body control module (BCM)

DTC B1821 seriousness

The seriousness of DTC B1821 can vary depending on the vehicle’s use and the importance of the rear wiper function. While it may not affect the vehicle’s overall drivability, it can hinder visibility in adverse weather conditions, making it a safety concern. It is advisable to address this issue promptly to ensure proper functionality of the rear wiper system.

How to diagnose DTC B1821

To diagnose DTC B1821, follow these steps:

1. Use an OBD-II scanner to confirm the presence of the B1821 code.
2. Inspect the wiring and connectors related to the rear wiper motor and relay for any visible damage or corrosion.
3. Check the rear wiper motor for proper operation by applying direct power to it.
4. Test the relay for continuity and proper function.
5. Examine the body control module for any faults or issues.

How to fix DTC B1821 step-by-step instructions

To fix DTC B1821, follow these step-by-step instructions:

1. Disconnect the vehicle’s battery to ensure safety while working on electrical components.
2. Inspect and repair any damaged wiring or connectors in the rear wiper motor circuit.
3. Replace the rear wiper motor if it is found to be faulty during testing.
4. Replace the relay if it fails the continuity test.
5. Reconnect the battery and clear the DTC using an OBD-II scanner.
6. Test the rear wiper system to ensure it operates correctly.

How to erase DTC B1821

To erase DTC B1821, follow these steps:

1. Connect an OBD-II scanner to the vehicle’s diagnostic port.
2. Turn on the vehicle’s ignition without starting the engine.
3. Navigate to the trouble codes section on the scanner.
4. Select the option to clear or erase the codes.
5. Confirm the action and wait for the scanner to complete the process.
6. Disconnect the scanner and start the vehicle to ensure the code does not reappear.

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