The B1748 diagnostic trouble code (DTC) indicates a fault within the passenger side mirror's horizontal adjustment circuit. Specifically, it signals that the electrical circuit responsible for moving the mirror glass left and right has shorted to ground. This issue can prevent the passenger side mirror from adjusting horizontally, impacting driver visibility and potentially creating a safety hazard.
This article will delve into the causes, symptoms, diagnostic procedures, and potential solutions for the B1748 DTC. Understanding these aspects is crucial for effectively troubleshooting and resolving this issue, ensuring the proper functionality of your vehicle's passenger side mirror.
B1748 DTC: Key Information
| Topic | Description | Possible Causes |
|---|---|---|
| Definition | Passenger side mirror horizontal adjustment circuit short to ground. This means the circuit intended to control the left/right movement of the passenger side mirror has an unintended electrical connection to the vehicle's ground. | Damaged wiring, faulty mirror switch, shorted mirror motor, corroded connections, water intrusion. |
| Common Symptoms | Passenger side mirror unable to adjust horizontally, mirror moves erratically, fuse blowing (related to mirror circuit), mirror stuck in one position, check engine light illuminated (in some vehicles). | |
| Diagnostic Steps | Visual inspection of wiring and connectors, testing the mirror switch, checking the mirror motor, circuit testing for shorts to ground, verifying power and ground to the mirror, scanning for other DTCs, and inspecting the Body Control Module (BCM). | |
| Possible Solutions | Repair or replace damaged wiring, replace the mirror switch, replace the mirror motor, clean or repair corroded connections, dry out water intrusion, replace blown fuse, reprogram or replace the Body Control Module (BCM) (rare). | |
| Component Location | The mirror switch is typically located on the driver's side door panel. The mirror motor is housed within the passenger side mirror assembly. Wiring runs from the switch, through the door harness, to the mirror motor. The BCM is typically located under the dashboard. | |
| Impact on Safety | Impaired visibility due to the inability to adjust the passenger side mirror can create a safety hazard while driving. | |
| Related DTCs | B1747 (Mirror Driver Horizontal Switch Circuit Short To Ground), B1749 (Mirror Passenger Vertical Switch Circuit Short To Ground), B1746 (Mirror Driver Vertical Switch Circuit Short To Ground), other DTCs related to door module or Body Control Module (BCM) functionality. | |
| Tools Required | Multimeter, wiring diagram for the specific vehicle, wire strippers, crimpers, electrical tape, circuit tester, scan tool (OBDII reader). | |
| Difficulty Level | Intermediate. Requires knowledge of basic electrical troubleshooting and the ability to read wiring diagrams. | |
| Estimated Repair Time | 1-3 hours, depending on the complexity of the issue and the accessibility of the components. | |
| Potential Cost | $50 - $500, depending on the parts required (switch, motor, wiring harness) and whether the repair is performed by a professional mechanic or DIY. | |
| Voltage Testing Values | Refer to the vehicle-specific wiring diagram. Typically, the mirror switch will have a 12V power supply. The voltage on the horizontal adjustment circuit wires will vary depending on the switch position. A short to ground will result in a 0V reading on the circuit wire. | |
| Resistance Testing Values | The mirror motor should have a specific resistance value, which can be found in the vehicle's service manual. A short to ground will result in a very low resistance reading (close to 0 ohms) between the circuit wire and the vehicle's ground. The wiring harness should have a very high resistance to ground unless the mirror switch is activated. | |
| Wiring Color Conventions | These vary greatly by vehicle manufacturer and model year. Always consult the vehicle-specific wiring diagram. Common colors for mirror circuits include blue, brown, white, black, and green, but these are not universal. |
Detailed Explanations
Definition: The B1748 code means there's an unintended electrical path from the passenger side mirror's horizontal adjustment circuit to the vehicle's chassis ground. This short circuit prevents the intended voltage from reaching the mirror motor to control its left/right movement.
Common Symptoms: The most obvious symptom is the passenger side mirror's inability to adjust horizontally. Other symptoms can include erratic mirror movement, a blown fuse related to the mirror circuit, the mirror being stuck in one position, or, in some vehicles, the illumination of the check engine light.
Diagnostic Steps:
- Visual Inspection: Carefully examine the wiring and connectors associated with the passenger side mirror. Look for any signs of damage, such as frayed wires, cracked insulation, or corroded connections. Pay close attention to the wiring harness where it passes through the door jamb, as this area is prone to wear and tear.
- Mirror Switch Testing: Use a multimeter to test the mirror switch. Ensure it's receiving power and sending the correct signals when activated. Consult the vehicle's wiring diagram for specific voltage values.
- Mirror Motor Testing: Disconnect the mirror motor and use a multimeter to check its resistance. A short to ground within the motor will result in a very low resistance reading. Also, try applying power directly to the motor to see if it functions correctly.
- Circuit Testing for Shorts to Ground: With the mirror switch disconnected, use a multimeter to check for continuity between the horizontal adjustment circuit wire and the vehicle's ground. A reading of close to 0 ohms indicates a short to ground.
- Verify Power and Ground: Ensure the mirror switch and motor are receiving proper power and ground connections. Use a multimeter to check for voltage and continuity.
- Scan for Other DTCs: Use an OBDII scanner to check for any other DTCs that may be related to the mirror circuit or the Body Control Module (BCM).
- Body Control Module (BCM) Inspection: In rare cases, the BCM may be faulty and causing the short circuit. Inspect the BCM for any signs of damage or corrosion.
Possible Solutions:
- Repair or Replace Damaged Wiring: If you find any damaged wiring, repair it using proper wiring techniques, such as soldering and heat shrinking. If the damage is extensive, replace the entire wiring harness.
- Replace the Mirror Switch: If the mirror switch is faulty, replace it with a new one.
- Replace the Mirror Motor: If the mirror motor is shorted to ground, replace it with a new one.
- Clean or Repair Corroded Connections: Clean any corroded connections with a wire brush and apply dielectric grease to prevent future corrosion.
- Dry Out Water Intrusion: If water intrusion is suspected, dry out the affected area and seal any leaks.
- Replace Blown Fuse: If the fuse related to the mirror circuit is blown, replace it with a new fuse of the correct amperage rating.
- Reprogram or Replace the Body Control Module (BCM): This is a rare solution and should only be considered after all other possibilities have been ruled out.
Component Location: The mirror switch is usually located on the driver's side door panel. The mirror motor is housed within the passenger side mirror assembly. Wiring runs from the switch, through the door harness, to the mirror motor. The Body Control Module (BCM) is typically located under the dashboard. Locating the BCM can vary greatly by vehicle make and model.
Impact on Safety: The inability to adjust the passenger side mirror can significantly impair a driver's visibility, especially when changing lanes or merging onto highways. This reduced visibility increases the risk of accidents.
Related DTCs: Other DTCs related to mirror functionality include B1747 (Mirror Driver Horizontal Switch Circuit Short To Ground), B1749 (Mirror Passenger Vertical Switch Circuit Short To Ground), and B1746 (Mirror Driver Vertical Switch Circuit Short To Ground). Also, look for codes related to the door module or Body Control Module (BCM).
Tools Required: A multimeter is essential for testing voltage, resistance, and continuity. A wiring diagram for the specific vehicle is crucial for identifying the correct wires and components. You'll also need wire strippers, crimpers, electrical tape, and a circuit tester. An OBDII scan tool is helpful for reading and clearing DTCs.
Difficulty Level: Troubleshooting the B1748 code is generally considered intermediate. It requires a basic understanding of electrical circuits and the ability to read wiring diagrams.
Estimated Repair Time: The repair time can vary depending on the complexity of the issue and the accessibility of the components. A simple wiring repair may take only an hour, while replacing the mirror motor or BCM could take several hours. Estimate 1-3 hours.
Potential Cost: The cost of repair depends on the parts required and whether you perform the repair yourself or hire a professional mechanic. A new mirror switch or motor can range from $50 to $200. If the BCM needs to be replaced, the cost could be significantly higher, potentially exceeding $500. Estimate $50 - $500.
Voltage Testing Values: Refer to the vehicle-specific wiring diagram for accurate voltage values. Typically, the mirror switch will have a 12V power supply. The voltage on the horizontal adjustment circuit wires will vary depending on the switch position. A short to ground will result in a 0V reading on the circuit wire.
Resistance Testing Values: The mirror motor should have a specific resistance value, which can be found in the vehicle's service manual. A short to ground will result in a very low resistance reading (close to 0 ohms) between the circuit wire and the vehicle's ground. The wiring harness should have a very high resistance to ground unless the mirror switch is activated.
Wiring Color Conventions: Wiring color conventions vary greatly by vehicle manufacturer and model year. Always consult the vehicle-specific wiring diagram. Common colors for mirror circuits include blue, brown, white, black, and green, but these are not universal.
Frequently Asked Questions
What does the B1748 code mean? It indicates a short to ground in the passenger side mirror's horizontal adjustment circuit, preventing the mirror from moving left and right.
What are the most common causes of the B1748 code? Damaged wiring, a faulty mirror switch, or a shorted mirror motor are the most frequent culprits.
Can I fix the B1748 code myself? Yes, if you have experience with electrical troubleshooting and can read wiring diagrams.
Is it safe to drive with the B1748 code? Driving with a non-functional passenger side mirror can be unsafe due to reduced visibility.
How much will it cost to fix the B1748 code? The cost can range from $50 to $500, depending on the parts needed and whether you hire a mechanic.
Conclusion
The B1748 DTC indicates a significant electrical fault affecting the passenger side mirror's horizontal adjustment. Thorough diagnosis, starting with a visual inspection and progressing to circuit testing, is crucial for identifying the root cause. Addressing the issue promptly is essential for restoring proper mirror functionality and ensuring safe driving conditions. Always consult a vehicle-specific wiring diagram and service manual for accurate information and procedures.