B1748 — Mirror Passenger Horizontal Switch Circuit Short To Ground #

Note: The code description may differ depending on the vehicle manufacturer.

• Mirror Passenger Horizontal Switch Circuit Short To Ground (Generic/OEM standard)
• Passenger Mirror Horizontal Adjustment Switch Circuit Low (Ford)
• Right Mirror Horizontal Motor Switch Shorted to Ground (Toyota)
• Passenger Side Mirror Horizontal Movement Switch Electrical Fault (Honda)

Summary of code B1748 #

The B1748 diagnostic trouble code (DTC) signals that the circuit controlling the passenger side mirror’s horizontal adjustment switch is experiencing a short to ground. In other words, the electrical pathway for moving the right-side mirror left or right has an unwanted connection directly to the vehicle’s chassis, disrupting normal switch operation. This code is typically detected and logged by the Body Control Module (BCM), which manages various body-related electronics. Drivers may notice issues adjusting the passenger mirror horizontally from the switch, but vertical movement often remains unaffected. While this is not usually a critical safety concern, it can hinder visibility and driver comfort, especially when sharing the car with others.

Common symptoms for code B1748 #

A vehicle showing the B1748 code often exhibits subtle but annoying symptoms. Most drivers notice some or all of the following:

• Passenger side mirror does not move left/right when using the control switch
• Mirror may be stuck in one position horizontally
• Vertical adjustment (up/down) still works normally
• Clicking, buzzing, or no sound at all from the mirror motor when attempting adjustment
• Illuminated warning in the instrument cluster (sometimes a generic body electronics fault)
• Mirror switch may feel warm or stick in one position (rare)

Most likely causes for code B1748 #

The causes of a B1748 code are generally related to wiring or mechanical faults in the mirror adjustment circuit. Ranked from most to least common:

1. Damaged wiring harness in the door or mirror assembly, causing a short to ground
2. Faulty mirror adjustment switch (internal short within the switch mechanism)
3. Water intrusion in the mirror or door connector, leading to corrosion or electrical shorts
4. Defective mirror adjustment motor (internal short in the horizontal drive motor)
5. Improper installation or previous repair causing pinched or misrouted wires
6. Body Control Module (BCM) fault (rare)

Step-by-step diagnostic process for code B1748 #

Diagnosing a B1748 code requires a methodical approach to avoid unnecessary part replacements. Here’s how a professional would proceed:

1. Verify the code using a scan tool and note any related codes (especially B-series or mirror-related codes).
2. Test the mirror adjustment switch: Does it work for other directions (vertical/up-down)?
3. Inspect the mirror switch and harness connector for signs of corrosion, water, or damage.
4. Check the wiring harness between the body and the door for pinched, frayed, or broken wires (especially at the door jamb).
5. Test for continuity and shorts to ground using a multimeter on the horizontal adjustment circuit.
6. Disconnect the mirror motor: If the short disappears, the motor may be faulty; if not, continue tracing the wiring.
7. If no wiring faults are found, test the switch and motor individually for internal shorts.
8. As a last step, consider a possible BCM issue if all components test good.

Possible repairs for code B1748 #

Once the root cause is identified, repairs for B1748 typically target the faulty component or wiring section:

• Repair or replace damaged wiring/connectors in the door or mirror assembly
• Replace the passenger mirror adjustment switch if found defective
• Clean and reseal connectors to prevent moisture ingress
• Replace the passenger mirror motor if it has an internal short
• Correct any installation errors or misrouted wires from previous work
• In rare cases, reprogram or replace the BCM if proven faulty (only after all other possibilities are ruled out)

Is it safe to drive with code B1748? #

Yes, you can continue driving with code B1748, as it will not directly impact your vehicle’s core safety or drivability. However, the inability to adjust the passenger side mirror horizontally can compromise visibility, especially if the mirror is stuck in an unusable position. It’s best to address the issue promptly, particularly if you regularly share the car or need to change the mirror’s angle for parking or lane changes.

Vehicles most commonly affected by code B1748 #

While B1748 is a generic code, it’s most frequently reported in vehicles fitted with power mirrors and multiplexed body electronics. Models that commonly experience this issue include:

• Ford (especially F-series trucks and Focus/Escape models)
• Toyota Camry, Corolla, and RAV4
• Honda Accord and Civic (2008–2017)
• Nissan Altima and Rogue
• Chevrolet Malibu, Equinox
• Hyundai Elantra and Sonata

Common mistakes & best practices for code B1748 #

Technicians and DIYers can sometimes misdiagnose or overlook the real culprit when dealing with B1748. Avoid these common errors:

• Replacing the mirror motor or switch without first checking the wiring and connectors
• Ignoring signs of water or corrosion inside the door or at harness junctions
• Missing intermittent shorts caused by pinched wires at the door hinge
• Not fully clearing the code after repair, leading to confusion if it reappears
• Overlooking related codes that may indicate a broader electrical issue

Express FAQ for code B1748 #

Still have quick questions? Here are answers to the most common ones:

• Q: Will code B1748 cause my check engine light to illuminate?
  A: No, B-codes like B1748 usually trigger a separate body or electronics warning, not the check engine light.
• Q: Can I reset the code myself after fixing the issue?
  A: Yes, you can use an OBD-II scanner to clear B-codes after repair. If the underlying problem remains, the code will return.
• Q: Could a blown fuse trigger this code?
  A: Rarely. A blown fuse typically disables all mirror movement. B1748 points to a short, not an open circuit.