B1789 – Mirror Passenger Down Circuit Short To Ground

The ODBII code B1789 indicates a malfunction in the passenger side mirror’s down movement circuit, specifically a short to ground, which means there is an unintended connection to the vehicle’s ground, causing the circuit to malfunction.

The severity of ODBII code B1789 is generally considered moderate.

Common Causes For: B1788 Mirror Passenger Down Circuit Short To Battery

• Damaged wiring or connectors
• Shorted or faulty switch
• Malfunctioning mirror motor
• Corroded terminals
• Water intrusion or moisture damage
• Faulty body control module (BCM)

Common misdiagnosis for B1789 Mirror Passenger Down Circuit Short To Ground

• Faulty passenger side mirror switch
• Damaged wiring harness
• Defective body control module (BCM)
• Shorted wiring in the door panel
• Malfunctioning power window motor
• Incorrectly installed or faulty mirror assembly
• Issues with the vehicle’s electrical system or grounding points

Common Troubleshooting Steps

The OBD-II code B1789 indicates a problem with the passenger side mirror’s down circuit, specifically a short to ground. Here are some common troubleshooting steps to diagnose and resolve this issue:

• Visual Inspection: **Wiring and Connectors: Inspect the wiring harness and connectors leading to the passenger side mirror. Look for any signs of damage, fraying, or corrosion.
• **Mirror Assembly: Check the mirror assembly itself for any physical damage that could cause a short circuit.
• Check for Short to Ground: **Multimeter Testing: Use a multimeter to check for continuity between the down circuit wire and ground. If there is continuity, it indicates a short to ground.
• **Inspect Ground Points: Ensure that all ground points related to the mirror circuit are clean and secure.
• Test the Mirror Motor: **Motor Functionality: If accessible, test the mirror motor by applying direct power to it. If the motor operates correctly, the issue may lie in the wiring or control module.
• **Resistance Check: Measure the resistance of the mirror motor. If it is too low (indicating a short), the motor may need to be replaced.
• Check the Switch: **Switch Functionality: Test the mirror control switch for proper operation. A faulty switch can cause incorrect signals to be sent to the mirror motor.
• **Wiring to Switch: Inspect the wiring between the switch and the mirror for any damage or shorts.
• Scan for Additional Codes: **Check for Other Codes: Use an OBD-II scanner to check for any additional trouble codes that may provide more context to the issue.
• Inspect the Body Control Module (BCM): **BCM Functionality: If all wiring and components appear to be in good condition, the issue may lie within the BCM. Check for any software updates or faults in the module.
• **Reprogramming: In some cases, reprogramming or resetting the BCM may resolve the issue.
• Repair or Replace Components: **Repair Wiring: If any damaged wiring or connectors are found, repair or replace them as necessary.
• **Replace Faulty Parts: If the mirror motor or switch is determined to be faulty, replace them.
• 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.
• Consult a Professional: If the issue persists after following these steps, it may be best to consult a professional mechanic or technician for further diagnosis. By following these troubleshooting steps, you should be able to identify and resolve the issue related to the B1789 code.