B1747 — Mirror Passenger Horizontal Switch Circuit Short To Battery

The diagnostic trouble code B1747 indicates a problem within the electrical circuit of the passenger side mirror’s horizontal (left-right) adjustment switch. In simple terms, the vehicle’s computer has detected a short circuit to the battery voltage in this specific circuit, which can affect the mirror’s ability to adjust properly. It’s important to note that labeling and coding may vary between vehicle manufacturers, so this code could appear differently depending on the OEM.

Manufacturer variations for trouble code B1747

The specific label or DTC for B1747 can differ depending on the vehicle manufacturer and model. Some OEMs may assign different codes with similar meanings, or integrate this fault into broader systems. Here are known variations:

• Ford/Mercury: May use similar codes related to mirror circuit faults but labeled differently within manufacturer-specific diagnostic definitions.
• Volkswagen Group: Could be classified under a different code relating to mirror or electrical circuit faults.
• GM (General Motors): Often aligns with codes indicating short circuits in mirror control circuits, though specific label may vary.

What does trouble code B1747 mean?

In straightforward terms, B1747 signals an electrical problem detected in the circuit that controls the passenger side mirror’s horizontal adjustment switch. The vehicle’s ECU (Engine Control Unit), or more precisely the Body Control Module (BCM), constantly monitors the electrical circuits for irregularities like shorts or open circuits. When it notices that the circuit wiring or switch is providing inconsistent or excessive current—often caused by a short circuit to the battery—it triggers this code.

This fault typically appears when the switch or wiring associated with the passenger mirror’s left-right adjustment is compromised. Such issues might be caused by damaged wiring insulation, a stuck or faulty switch, or a short circuit caused by corrosion, debris, or electrical faults. The trigger point is the presence of a direct connection from the circuit to the positive terminal of the battery, which is abnormal and potentially hazardous.

In what typical scenarios does this code appear? It often manifests after the installation or repair of mirrors, interior wiring work, or in older vehicles where wiring insulation has degraded over time. Sometimes, it can also appear after electrical faults elsewhere, such as a fuse blow or a shorted relay that influences the mirror circuit.

Severity and risks of trouble code B1747

The B1747 fault primarily affects the operation of the passenger mirror’s horizontal control. While it is not directly critical for vehicle safety or drivability, neglecting electrical issues can lead to more severe problems, such as wiring fires or damage to control modules. In some cases, the short circuit might cause blown fuses or even damage the associated switch or BCM if left unaddressed.

As for whether the vehicle can be driven, it’s typically safe to drive but with limited functionality. The main concern is the mirror adjustment feature being inoperative, which could reduce driver awareness in certain situations. If the wiring or circuit is causing an electrical overload, it’s recommended to address the fault promptly to prevent further damage.

**Conclusion:** Limited — the vehicle can generally be driven but with the potential for electrical system issues if unresolved.

Symptoms of trouble code B1747

Most drivers will notice certain signs that hint at this issue, especially related to the mirror’s electrical functions. Key symptoms can include:

• Passenger mirror does not respond to adjustment controls
• Warning light or indicator related to mirror controls may illuminate on the dashboard
• Intermittent or complete failure of the horizontal mirror movement
• Possible electrical smells or burning odours if wiring insulation is damaged
• Fuses related to the mirror system may blow repeatedly
• Unusual behavior of other electrical components in proximity to the mirror circuit

Most likely causes of trouble code B1747

The presence of B1747 suggests an issue within the passenger side mirror electrical circuit, particularly the horizontal adjustment switch. Here are the most common causes, ranked from most to least probable:

1. Short Circuit in the Wiring Harness: Damage or insulation degradation in the wire connecting the switch to the BCM can cause a direct short to the battery voltage.
2. Faulty Passenger Mirror Switch: The switch itself may be internally shorted, especially if it is stuck or physically damaged.
3. Corroded or Damaged Connectors: Corrosion or loose connections at the connectors can cause intermittent shorts or open circuits.
4. Wiring Damage or Chafing: Worn or pinched wiring, particularly in areas where wiring passes through door bodies, may cause short circuits.
5. Battery or Electrical System Issues: Underlying electrical faults, such as a failing fuse or relay, could be contributing to abnormal voltages in the circuit.

How to diagnose trouble code B1747

Diagnosing this fault involves a systematic approach to identify the root cause without risking further damage. The following generic steps can be undertaken:

1. Visual Inspection: Check the wiring harness related to the passenger mirror, looking for signs of damage, chafing, or corrosion.
2. Check the Connectors: Ensure all electrical connectors are secure, free of corrosion, and properly seated.
3. Test the Switch: Use a multimeter to verify the switch’s operation and check for internal shorts or open circuits.
4. Live Data Monitoring: Connect an OBD2 scanner with live data capabilities to observe the mirror control signals and circuit voltage during operation.
5. Continuity and Resistance Tests: With the vehicle turned off, test continuity and resistance in wiring between the switch and the BCM to locate faults.
6. Fusible and Circuit Checks: Verify relevant fuses and relays are intact and functioning properly.

Possible repairs for trouble code B1747

Based on the probable causes, repairs can range from simple fixes to more involved replacements. Always prioritize safety and proper diagnostics before repairs.

• Replace or Repair Wiring: Repair damaged wiring or replace faulty wiring harnesses. *Professional repair recommended*
• Replace Faulty Switch: If the switch is internally shorted or damaged, replacing it is usually necessary. *Basic repair for qualified technicians*
• Clean or Replace Connectors: Remove corrosion, secure loose connections, or replace damaged connectors. *Basic electrical repair*
• Check and Replace Fuses/Relays: Replace blown fuses or faulty relays associated with the mirror circuit.
• Inspect and Repair Door Wiring: For chafed or damaged wiring in the door frame, repair or replace wiring harnesses. *Requires professional expertise*
• Electrical System Check: Investigate broader electrical issues that may cause shorts, possibly involving the vehicle’s battery or alternator. *Professional diagnosis recommended*

Vehicles commonly associated with trouble code B1747 in Europe

This code appears in a variety of European vehicles, especially those equipped with electronically controlled mirrors. The most frequently affected brands include:

Volkswagen Group: Models within the Golf, Passat, Polo, and Tiguan families.

Ford: Particularly in models with electric mirrors, such as Fiesta, Focus, and Mondeo.

Opel/Vauxhall: Including Astra, Corsa, Insignia, and others.

Because of its generic nature, this fault might also occur in various other makes with electric mirror systems, especially in older or high-mileage vehicles.

Frequent mistakes with trouble code B1747

When diagnosing and repairing this fault, some common mistakes can compromise the process. Avoid these pitfalls:

• Assuming the switch is the only cause without thorough wiring checks
• Ignoring the possibility of wiring damage inside door panels or hidden locations
• Not verifying fuse and relay integrity, leading to misdiagnosis
• Replacing parts without confirming the circuit’s integrity, risking recurring faults

FAQ — trouble code B1747

Can this code disappear on its own? Generally, no. This kind of electrical short typically persists until the faulty wiring, switch, or connector is repaired. It may temporarily reset if the short is intermittent, but underlying issues will cause the code to return.

Can I keep driving? It’s usually safe to drive if the mirror adjustment is not essential, but it’s advisable to get the fault diagnosed and repaired to avoid electrical damage or wiring hazards.

Why does the code return after clearing? Because the underlying cause—such as a damaged wire or faulty switch—remains, the ECU will detect the same short circuit again and re-trigger the fault.