Introduction
The B1550 Diagnostic Trouble Code (DTC) indicates a fault within the circuit related to the mirror select switch, specifically concerning the selection of either the left or right front mirror. This switch allows the driver to choose which side mirror's adjustments are controlled by the mirror adjustment controls. A malfunctioning circuit can prevent proper mirror adjustment, impacting visibility and potentially posing a safety risk. Diagnosing and resolving this issue often requires a systematic approach involving checking wiring, the switch itself, and related control modules.
Table: B1550 Diagnostic Trouble Code Details
| Category | Description | Possible Causes |
|---|---|---|
| Code Definition | B1550 - Mirror Left Front or Right Front Select Switch Circuit. Indicates a malfunction in the electrical circuit responsible for signaling the vehicle's computer which side mirror (left or right) is selected for adjustment. | Faulty Mirror Select Switch: The switch itself may be damaged, worn, or have internal electrical faults. Wiring Issues: Open circuits, short circuits, or high resistance in the wiring harness connecting the mirror select switch to the body control module (BCM) or other relevant control module. This could include damaged connectors, corroded terminals, or broken wires. BCM Malfunction: Although less common, a fault within the BCM or other relevant module responsible for processing the mirror select switch signal could trigger this code. Grounding Issues: Poor or absent ground connections for the mirror select switch circuit. * Power Supply Issues: Insufficient or fluctuating power supply to the mirror select switch circuit. |
| Symptoms | Inability to adjust one or both side mirrors. Only one side mirror can be adjusted regardless of switch position. Intermittent mirror adjustment functionality. Mirror moves erratically or in the wrong direction. The mirror select switch has no effect on mirror adjustment. The vehicle's computer (ECU/BCM) stores the B1550 trouble code. * Other electrical issues may be present, such as problems with other door functions (windows, locks). | |
| Troubleshooting | Visual Inspection: Carefully inspect the mirror select switch, wiring harness, and connectors for any signs of damage, corrosion, or loose connections. Switch Testing: Use a multimeter to test the continuity and resistance of the mirror select switch in different positions. Compare readings to the vehicle's service manual specifications. Wiring Testing: Use a multimeter to check for continuity, shorts to ground, and shorts to power in the wiring harness connecting the mirror select switch to the BCM. BCM Testing: If wiring and the switch are ruled out, the BCM may need to be tested or reprogrammed by a qualified technician. Ground and Power Supply Checks: Verify the integrity of the ground and power supply circuits for the mirror select switch circuit. Scan Tool Diagnostics: Use a scan tool to read the B1550 code and any other related codes. The scan tool can also be used to monitor the mirror select switch signal to the BCM. |
Detailed Explanations
Code Definition: The B1550 code specifically points to an issue within the electrical circuit that controls the selection of the left or right front mirror. This circuit communicates the driver's selection to the vehicle's computer, typically the Body Control Module (BCM) or a similar control module. This selection determines which mirror will respond to adjustment commands.
Symptoms: The most obvious symptom is the inability to adjust one or both side mirrors. You might find that only one mirror can be adjusted, regardless of the switch position. Intermittent functionality, where the mirror works sometimes but not others, is also a common indicator. Erratic mirror movement or movement in the wrong direction can also occur. Crucially, the mirror select switch may have no effect at all on mirror adjustment. The presence of the B1550 code stored in the vehicle's computer confirms the issue. In some cases, other electrical problems related to door functions (windows, locks) might also be present.
Faulty Mirror Select Switch: The mirror select switch itself is a prime suspect. Over time, the switch's internal contacts can wear down or become corroded, leading to intermittent or complete failure. Physical damage, such as cracks or broken components, can also compromise its functionality.
Wiring Issues: Wiring problems are a frequent cause of the B1550 code. This includes open circuits (broken wires preventing electrical flow), short circuits (wires contacting each other or ground), and high resistance (corrosion or loose connections hindering electrical flow). Damaged connectors, corroded terminals, and broken wires within the wiring harness are all potential culprits.
BCM Malfunction: While less common than switch or wiring issues, a fault within the Body Control Module (BCM) or a similar module responsible for processing the mirror select switch signal can trigger the B1550 code. The BCM interprets the signal from the mirror select switch and relays the appropriate commands to the mirror motors.
Grounding Issues: Proper grounding is crucial for any electrical circuit to function correctly. A poor or absent ground connection for the mirror select switch circuit can disrupt the signal flow and lead to the B1550 code.
Power Supply Issues: The mirror select switch circuit requires a stable and adequate power supply. Insufficient or fluctuating power can cause the switch to malfunction and trigger the error code.
Visual Inspection: The first step in troubleshooting is a thorough visual inspection. Carefully examine the mirror select switch itself, looking for any signs of physical damage. Next, inspect the wiring harness and connectors associated with the switch. Look for damaged wires, corroded terminals, or loose connections.
Switch Testing: Use a multimeter to test the continuity and resistance of the mirror select switch in different positions. Compare your readings to the specifications outlined in the vehicle's service manual. This will help determine if the switch is functioning correctly.
Wiring Testing: Employ a multimeter to check for continuity, shorts to ground, and shorts to power in the wiring harness connecting the mirror select switch to the BCM. Continuity testing ensures that the wires are intact and allowing electrical flow. Shorts to ground indicate a wire is contacting the vehicle's chassis, while shorts to power indicate a wire is contacting a positive voltage source.
BCM Testing: If you've ruled out wiring and switch problems, the BCM may be the source of the issue. BCM testing and reprogramming should be performed by a qualified technician with the necessary diagnostic equipment and expertise.
Ground and Power Supply Checks: Verify the integrity of the ground and power supply circuits associated with the mirror select switch circuit. Ensure that the ground connections are clean and secure, and that the power supply voltage is within the specified range.
Scan Tool Diagnostics: Using a scan tool is crucial for diagnosing the B1550 code. The scan tool can read the code and any other related codes, providing valuable insights into the problem. It can also be used to monitor the mirror select switch signal as it's being received by the BCM, allowing you to see if the switch is sending the correct signals.
Frequently Asked Questions
What does the B1550 code mean? The B1550 code indicates a problem with the mirror select switch circuit, preventing proper selection of the left or right front mirror for adjustment.
Can I fix the B1550 code myself? Depending on your mechanical skills, you might be able to fix it by checking wiring and the switch, but BCM issues require professional help.
What are the most common causes of the B1550 code? The most common causes are a faulty mirror select switch or wiring problems in the circuit.
How do I test the mirror select switch? Use a multimeter to check the continuity and resistance of the switch in different positions, comparing the readings to the vehicle's service manual.
Will the B1550 code affect other vehicle functions? While primarily affecting mirror adjustment, it could potentially indicate broader electrical issues if related to the BCM or wiring harness.
Conclusion
The B1550 code signifies a problem with the mirror select switch circuit, hindering proper mirror adjustment. Thoroughly inspect the switch and wiring before considering more complex issues with the BCM, and consult a qualified technician if needed.