B1789

Code

Other B — Body

Mirror Passenger Down Circuit Short To Ground

Brand: Other

Type: B — Body

Views: UK: 18 EN: 26 RU: 12

AI status

Completed

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Page language: EN

Causes

Wiring short to ground on the passenger mirror down circuit
Faulty passenger mirror motor or mirror control module
Corroded or damaged connector or terminal
Faulty body control module (BCM) or mirror driver circuit
Aftermarket accessory or repair caused pin damage or chafe

Symptoms

Passenger side mirror does not move/tip down when commanded
Mirror operation intermittent or works in other directions but not down
Blown fuse or repeated fuse failures related to mirror circuit
Stored mirror-related warning lamp or reduced mirror functionality
Possible BCM stored faults or related communication warnings

What to check

Scan vehicle and confirm B1789 and any related mirror or BCM codes; record freeze-frame data
Perform visual inspection of passenger mirror, connector, and wiring through the door hinge area
Check for blown fuses related to mirror circuits
Backprobe mirror connector and measure voltages while commanding mirror down
Measure resistance between down circuit and chassis ground with connector disconnected
Disconnect passenger mirror; if fault clears, suspect mirror or connector; if persists, suspect wiring or BCM

Signal parameters

Battery nominal voltage: ~11–14.5 V (vehicle off/on as applicable)
Inactive down control: near 0 V (high impedance) or expected reference depending on design
Active 'down' command: supply voltage ~12 V or PWM applied to mirror motor/driver
Motor coil resistance (typical): low ohms; expect a finite resistance (often 2–30 Ω) between motor terminals — near 0 Ω indicates shorted coil
Open-circuit to ground: high resistance (kΩs); short to ground: very low resistance (Ωs)

Diagnostic algorithm

Retrieve freeze-frame and pending codes. Verify B1789 is current and attempt to reproduce the symptom.
Visually inspect passenger mirror, harness, and connector for damage, corrosion, water intrusion, or pin deformation—pay attention to the door hinge area.
With ignition ON, backprobe the mirror down circuit at the mirror connector and observe voltage while commanding mirror down from switch/vehicle controls. Note behavior.
With harness disconnected from mirror and ignition OFF, measure DC resistance between the down circuit wire and chassis ground. Expect very high resistance; a low reading indicates a short to ground in the harness or module.
If a short is confirmed with the mirror disconnected, trace the harness toward the body control module. Inspect for chafed insulation, repair/replace damaged section and re-test.
If resistance is normal with mirror disconnected, reconnect mirror and test again. If short appears only when mirror is connected, suspect mirror internal short or connector fault—remove mirror for bench testing or replace mirror.
If wiring appears good and mirror tests fine, check BCM/mirror driver outputs. Verify the control module output pin for shorts using a fused jumper or a current-limited bench supply; replace module only after confirming circuitry fault.
After repair, clear codes and verify proper mirror operation and that B1789 does not return.
Safety note: avoid applying unfused battery power to circuits. Use proper fusing and current-limited test equipment to prevent damage.

Likely causes

Insulation worn through where harness rubs against body sheet metal causing contact with ground
Bent or pushed-out terminal in mirror connector creating a short to ground
Water intrusion causing corrosion and shorting at mirror connector
Internal mirror motor or actuator failure creating a low-resistance path to ground
Short in wiring near door hinge / door jamb where wires flex during door movement
Incorrectly wired aftermarket mirror or alarm/remote module

Fault status

⚠️ Status

Passenger mirror 'down' circuit has a short to ground. Inspect mirror, connector, and wiring for damage or corrosion. Do not repeatedly operate the mirror until repaired to avoid blowing fuses or damaging the driver/module.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours