B1739 — Mirror Driver Horizontal Switch Circuit Short To Battery #

Note: The code label may vary depending on the vehicle manufacturer.

• Mirror Driver Horizontal Switch Circuit Short To Battery (General/OEMs)
• Driver’s Mirror Horizontal Adjustment Switch Circuit High (Ford)
• Driver Side Mirror Horizontal Motor Switch – Circuit Short to Battery (Chrysler/Jeep)
• Mirror Adjustment Switch Short to Positive (Honda)

Code summary for B1739 #

The B1739 diagnostic trouble code (DTC) relates to the driver’s side mirror horizontal adjustment switch circuit. This code triggers when the vehicle’s body control module (BCM) or door control module detects a short to battery voltage in the horizontal (left-right) mirror switch circuit. In simple terms, the circuit is receiving more voltage than it should, likely because a wire or switch is contacting battery power directly. While this code primarily affects mirror adjustment, it can indicate underlying wiring issues that might affect related electrical systems. Addressing B1739 promptly helps maintain the comfort and safety features of your vehicle.

Common symptoms for code B1739 #

When B1739 sets, you’ll typically notice issues with the horizontal adjustment of the driver’s side mirror. Other electrical quirks may arise, depending on wiring configuration. Expect one or more of the following symptoms:

• Driver’s side mirror does not move left or right
• Mirror moves without input or in only one direction
• Mirror adjustment switch feels hot to the touch
• Related electrical accessories behaving oddly (rare)
• Warning or error message on dashboard (some models)

Probable causes for code B1739 #

The most common reason for B1739 is a short circuit in the wiring or switch for the driver’s mirror horizontal adjustment. Here’s how the causes usually stack up, from most to least likely:

1. Shorted or damaged wiring harness at the driver’s door or mirror
2. Defective driver’s mirror horizontal adjustment switch
3. Moisture or corrosion at electrical connectors
4. Mirror motor internal short (less common)
5. Pinched or chafed wiring after recent door repairs or window replacement
6. Faulty body control module (rare)

Step-by-step diagnostics for code B1739 #

A logical, thorough approach is key to resolving B1739. Here’s a basic step-by-step plan to track down the cause:

• 1. Visual inspection: Check the driver’s mirror switch, wiring, and connectors for obvious damage, moisture, or corrosion.
• 2. Check fuse integrity: Verify that all related fuses are intact and not showing signs of overheating.
• 3. Test switch operation: With a multimeter, confirm whether the switch is sending the correct signals when actuated.
• 4. Inspect wiring harness: Look for pinched, frayed, or shorted wires in the door hinge area and behind the door panel.
• 5. Disconnect mirror motor: Temporarily unplug the mirror motor to see if the code clears, indicating an internal motor short.
• 6. Scan for additional codes: Related codes can help pinpoint if the problem extends to other modules or circuits.
• 7. Consult OEM wiring diagrams: Compare voltage readings at each connector to expected values, per the manufacturer’s service manual.

Possible repairs for code B1739 #

Once the root cause is identified, repairs should be targeted accordingly. Typical solutions for B1739 include:

• Repairing or replacing damaged or shorted wiring in the mirror or door harness
• Replacing the driver’s mirror horizontal adjustment switch if faulty
• Cleaning and re-securing corroded connectors
• Replacing the mirror motor if it’s internally shorted
• Re-routing or securing harnesses to prevent future pinching or chafing
• Rarely, replacing the body control module (only if all other causes are eliminated)

Is it safe to drive with code B1739? #

Yes, you can generally continue driving with code B1739 present, as it does not affect engine performance, braking, or core vehicle safety systems. However, you will lose electrical adjustment of the driver’s side mirror horizontally, which may compromise visibility and safe lane-changing. If the mirror moves on its own or cannot be positioned for a clear rear view, address the issue promptly for your safety.

Vehicles most commonly affected by code B1739 #

This code is most frequently reported on vehicles with power-adjustable mirrors and advanced body electronics. While it can occur on any brand, it is most often seen on:

• Ford F-Series, Fusion, Explorer, Focus
• Chrysler 300, Jeep Grand Cherokee, Dodge Charger
• Honda Accord, CR-V (with power mirrors)
• Toyota Camry, Corolla (select trims)
• General Motors: Chevrolet Malibu, GMC Sierra

Common mistakes and best practices for B1739 #

Misdiagnosis is possible if basic inspection steps are skipped or if the code is cleared without identifying the root cause. Keep these tips in mind:

• Don’t replace the mirror motor or switch until you’ve checked wiring and connectors thoroughly
• Always use OEM wiring diagrams for your specific model year
• Inspect for water intrusion in the door, especially after heavy rain or recent glass replacement
• Verify that all electrical connectors are fully seated after repairs
• Retest the system after each repair to confirm the fault is resolved

FAQ for code B1739 #

Below are quick answers to common questions about this trouble code:

• Q: Can B1739 cause my other door controls (windows, locks) to stop working?
  A: Usually not, unless there is a broader wiring short in the door harness affecting multiple circuits.
• Q: Do I need to replace the whole mirror assembly?
  A: Not always—often, the problem is isolated to the switch or a section of wiring. Only replace the mirror if diagnostics confirm an internal short.
• Q: Will the code go away on its own?
  A: Only if the underlying short is fixed; simply clearing the code with a scan tool will not resolve the circuit problem.