B1640 — Mirror Passenger Left Circuit Open
The diagnostic trouble code B1640 indicates an issue with the electrical circuit connected to the passenger side mirror, specifically on the left side. In simple terms, this code means that the vehicle’s onboard computer (ECU) has detected an open (disconnected or faulty) circuit in the mirror’s electrical wiring. It is important to note that label variations may occur between different vehicle manufacturers, so the exact terminology used in the vehicle’s diagnostics or repair manual may vary.
- System affected: Mirror electrical circuit
- Severity: Moderate
- Main symptoms: Inoperative mirror, warning light on dashboard
- Driveability: No, but does not usually affect vehicle operation directly
Manufacturer variations for trouble code B1640
The B1640 code is a generic OBD-II code, meaning it can be used by multiple vehicle manufacturers. Although the core meaning remains consistent, some OEMs may assign different labels or code numbers for similar issues, or include additional diagnostic contexts in their specific systems. Here are some known variations:
- Ford: B1640 — Passenger Side Mirror Circuit Fault
- Volkswagen / Audi / SEAT / Skoda: 5F1 1640 — Passenger Mirror Circuit Open
- BMW: 611F — Passenger Side Mirror Circuit Open
- Mercedes-Benz: SRS / Mirror related codes, may vary
- Other OEMs: May use slightly different numerical codes or labels but generally refer to the same circuit issue
What does trouble code B1640 mean?
When the ECU detects a circuit open on the passenger side mirror’s wiring or connector, it will generate the B1640 code. This code signals that the electrical pathway needed to control or power the mirror has been interrupted. This interruption could be due to a disconnected wire, damaged connector, or faulty mirror motor.
The ECU monitors the electrical resistance within the mirror’s control circuit. If the resistance exceeds acceptable limits, indicating an open circuit, it will set this trouble code. Typically, this issue appears when trying to adjust the mirror, activate heating elements, or in models equipped with power-folding functions.
In most cases, the code appears during routine diagnostics or when the mirror stops functioning. It can also be triggered after a collision, door repair, or if wiring becomes worn or corroded over time.
Severity and risks of trouble code B1640
The B1640 code generally relates to a non-critical circuit issue affecting the mirror’s functionality.While it won’t prevent the vehicle from running, it can compromise driver visibility and safety, especially if the mirror cannot be adjusted or heated. This can lead to blind spots or reduced visibility in adverse weather conditions.
Risks include the possibility of further electrical problems if the wiring fault causes short circuits or other circuits to malfunction. However, the vehicle remains safe to operate in most cases. Can the vehicle be driven? Yes, but with caution, and repairs should be undertaken promptly to restore full functionality and safety.
Symptoms of trouble code B1640
The primary symptom of this trouble code is a non-operational or malfunctioning passenger side mirror. Drivers may notice that the mirror does not respond to control inputs, does not heat up, or folds improperly if it has folding functions.
- Inoperative mirror: Cannot adjust or move with control switches
- Mirror heating not working: No defrost or demisting capabilities in cold weather
- Warning lights: Dashboard indicator warning about mirror or electrical fault may appear
- Unusual noises: Sometimes, a relay or motor noise if attempts are made to adjust the mirror
Most likely causes of trouble code B1640
Understanding the root causes of B1640 can help technicians or vehicle owners address the problem efficiently. While causes may vary based on vehicle age and usage, the typical or most probable causes include:
- Damaged or disconnected wiring: Physical damage, wear, or accidental disconnection in the mirror’s wiring harness
- Faulty mirror switch or control module: Malfunction of the switch that controls the mirror adjustments
- Corroded or poor electrical connectors: Moisture or dirt ingress can cause poor contact in connector pins
- Broken or failed mirror motor or actuator: Internal failure preventing mirror adjustment or folding
- Blown fuse or relay: Electrical component that supplies power to the mirror circuit may be faulty
- Electrical short circuit or ground fault: Internal wiring faults leading to open circuit conditions
How to diagnose trouble code B1640
To accurately diagnose the cause of B1640, follow a systematic approach. Always start with a visual inspection and proceed with live data tests if possible. Here are generic diagnostic steps:
- Visual Inspection: Check the physical wiring, connectors, and mirror motor assembly for signs of damage, corrosion, or disconnection.
- Check Fuses and Relays: Verify the condition of the fuse and relay associated with the mirror circuit and replace if necessary.
- Test electrical continuity: Use a multimeter to check wiring continuity from the mirror to the main wiring harness, ensuring no breaks or shorts.
- Inspect connectors: Ensure all connectors are properly seated, clean, and free of corrosion or damage.
- Use live data / scan tool: With appropriate diagnostic equipment, verify if the mirror control signals are reaching the actuator and if the circuit shows an open condition.
- Check for additional codes: Scan for other related fault codes which might indicate wiring or module issues.
Possible repairs for trouble code B1640
Based on the identified causes, repairs can vary from simple to complex. Proper diagnosis will inform the appropriate fix. Common repairs include:
- Reconnect or replace wiring harness: Basic repair that involves re-securing or replacing damaged wiring and connectors. Suitable for minor physical damage.
- Replace mirror switch or control module: When the switch or control unit is faulty, these components should be replaced. Usually a professional job.
- Clean or repair electrical connectors: Removing dirt or corrosion and ensuring a snug fit can restore proper connectivity. Usually a DIY friendly repair.
- Replace mirror motor/actuator: If the motor has failed internally, a replacement is necessary. A more advanced repair requiring technical skills.
- Fix wiring faults: Repairing or replacing sections of wiring damaged by wear, rodents, or accidents. Often requires expertise and diagnostics.
- Replace blown fuse or relay: If the fuse or relay is blown, replacing it can resolve the circuit open condition. Simple fix.
Vehicles commonly associated with trouble code B1640 in Europe
This code is frequently encountered in a variety of European vehicles, particularly those equipped with power-adjustable mirrors. Processes and typical issues are similar across models, but some vehicle groups are more affected:
Volkswagen Group (VW, Audi, Seat, Skoda): Various models with electrically adjustable mirrors often show this code when wiring issues or actuator failures occur.
Ford:** Commonly on models with electric side mirrors, especially older models with wear or damage in wiring.
BMW:** On models with electrochromatic or power-adjustable mirrors, wiring or control module issues may generate this code.
Mercedes-Benz: May have similar mirror circuit fault codes related to wiring or motor problems.
Frequent mistakes with trouble code B1640
During diagnosis and repair, some common pitfalls can lead to prolonged repairs or further issues. Awareness of these mistakes can improve success rates:
- Assuming the problem is solely with the mirror: Often, wiring or the switch control is the root cause, not the mirror motor itself.
- Neglecting to check wiring before replacing components: Replacing parts without verifying wiring integrity can lead to recurring faults.
- Using incompatible parts: Installing non-OEM replacements or incompatible motors may cause further circuit issues.
- Failing to reset the ECU after repairs: Not clearing fault codes and verifying repair success can re-trigger the codes.
- Overlooking related codes: Additional fault codes may be present that need addressing concurrently.
FAQ — trouble code B1640
Can this code disappear on its own? If the cause of the open circuit is temporary, such as a loose connector or a minor wiring fault that gets resolved, the code might reset after driving and clearing the ECU. However, persistent issues require mechanical repair.
Can I keep driving? Yes, but with caution. The passenger mirror may not function correctly, which could impair safety. It’s recommended to repair the issue promptly.
Why does the code return after clearing? The underlying wiring problem, faulty switch, or motor failure may still be present. If not properly repaired, the fault will likely reappear.
Is it safe to ignore this code? While it usually does not affect the core vehicle operation, ignoring it can reduce safety, particularly if it affects mirror adjustment or heating. Repairing the circuit is advised.