The B2140 diagnostic trouble code (DTC) indicates a malfunction within the circuit controlling the "Up" function of a vehicle's power mirror(s). This code signifies an electrical issue preventing the mirror from moving upwards as intended, potentially affecting driver visibility and safety. Addressing this promptly is crucial for ensuring safe operation of the vehicle.
Table: B2140 - Mirror Up Control Switch Circuit Malfunction
| Component/Symptom | Description | Possible Cause |
|---|---|---|
| Mirror Up Control Switch | The physical switch used to command the mirror to move upwards. | Defective switch, internal short circuit, corrosion on contacts. |
| Mirror Up Motor | The electric motor responsible for physically moving the mirror upwards. | Failed motor, internal short circuit, mechanical binding. |
| Wiring Harness & Connectors | The wires and connectors connecting the switch, motor, and control module. | Damaged wiring (broken, frayed, shorted), loose or corroded connectors. |
| Power Mirror Control Module (If Applicable) | A dedicated module that controls the power mirror functions. Not all vehicles have a separate module; some integrate this into the body control module (BCM). | Faulty module, internal failure, software issue. |
| Fuse | A protective device in the electrical circuit. | Blown fuse due to excessive current draw. |
| Ground Connection | The connection to the vehicle's chassis, providing a return path for the electrical current. | Loose, corroded, or broken ground connection. |
| Symptom: Mirror Doesn't Move Up | The primary symptom; the mirror fails to adjust upwards when the switch is activated. | Any of the above causes. |
| Symptom: Intermittent Operation | The mirror sometimes moves up, and sometimes doesn't. | Loose connections, intermittent short circuit, marginal switch. |
| Symptom: Other Mirror Functions Affected | Other mirror functions (left/right/down) may also be affected. | Power Mirror Control Module failure, wiring harness issue affecting multiple circuits. |
| Scan Tool Data | Diagnostic trouble code (DTC) B2140 stored in the vehicle's computer. | Confirms the presence of a fault in the mirror up control circuit. |
| Multimeter Readings | Used to test voltage, continuity, and resistance in the circuit. | Helps pinpoint the location of the electrical fault. |
| Wiring Diagram | A schematic showing the electrical connections of the mirror circuit. | Essential for troubleshooting and identifying components. |
| Repair Procedure: Visual Inspection | Examining the wiring, connectors, and switch for obvious damage. | Identifies physical damage that could be causing the problem. |
| Repair Procedure: Switch Testing | Using a multimeter to test the switch for proper operation. | Determines if the switch is functioning correctly. |
| Repair Procedure: Motor Testing | Applying power directly to the motor to see if it operates. | Determines if the motor is functioning correctly. |
| Repair Procedure: Wiring Continuity Testing | Using a multimeter to test the continuity of the wiring harness. | Identifies broken or shorted wires. |
| Repair Procedure: Voltage Drop Testing | Measuring the voltage drop across the circuit to identify high resistance areas. | Locates areas of excessive resistance that can impede current flow. |
| Repair Procedure: Component Replacement | Replacing the faulty switch, motor, or control module. | Corrects the problem if the component is identified as the source of the fault. |
| Related DTCs | Other mirror-related DTCs may be present, providing further clues. | Helps narrow down the problem and identify related issues. |
Detailed Explanations
Mirror Up Control Switch: This is the physical interface used to command the mirror to move upwards. These switches are prone to wear and tear, especially with frequent use. Internal corrosion or physical damage can prevent the switch from sending the correct signal to the mirror motor or control module.
Mirror Up Motor: The mirror up motor is a small electric motor that physically moves the mirror glass upwards. These motors can fail due to age, overheating, or internal short circuits. Mechanical binding within the mirror assembly can also prevent the motor from operating correctly.
Wiring Harness & Connectors: The wiring harness and connectors provide the electrical pathways between the switch, motor, and control module. Damage to the wiring, such as broken or frayed wires, or corrosion on the connectors, can disrupt the flow of electricity and cause the B2140 code. Inspect the wiring for any signs of chafing or damage.
Power Mirror Control Module (If Applicable): Some vehicles use a dedicated control module to manage the power mirror functions. This module receives signals from the switch and controls the motor accordingly. A faulty module can misinterpret the signals or fail to send the correct commands to the motor, resulting in the B2140 code. Note that some vehicles integrate this functionality into the Body Control Module (BCM).
Fuse: A fuse is a safety device designed to protect the electrical circuit from overcurrent. A blown fuse indicates that there has been an excessive current draw in the circuit, which could be caused by a short circuit or a faulty component. Replacing a blown fuse without addressing the underlying cause may result in the fuse blowing again.
Ground Connection: A good ground connection is essential for the proper operation of any electrical circuit. A loose, corroded, or broken ground connection can create resistance in the circuit, which can interfere with the flow of electricity and cause the B2140 code. Ensure the ground connection is clean and secure.
Symptom: Mirror Doesn't Move Up: This is the most obvious symptom of the B2140 code. The mirror will not adjust upwards when the "up" button on the control switch is pressed. However, this symptom alone doesn't pinpoint the exact cause; further investigation is required.
Symptom: Intermittent Operation: An intermittent problem means the mirror may work sometimes, but not always. This could indicate a loose connection, a failing switch, or a motor that is beginning to fail. Intermittent problems can be challenging to diagnose because the fault may not be present when testing the circuit.
Symptom: Other Mirror Functions Affected: If other mirror functions, such as left/right/down movement, are also affected, it could indicate a problem with the power mirror control module or a wiring harness issue affecting multiple circuits. This can help narrow down the possible causes.
Scan Tool Data: A scan tool can be used to read the diagnostic trouble codes (DTCs) stored in the vehicle's computer. The presence of the B2140 code confirms that there is a fault in the mirror up control circuit. The scan tool may also provide additional information about the fault, such as the voltage readings from the circuit.
Multimeter Readings: A multimeter is an essential tool for diagnosing electrical problems. It can be used to measure voltage, continuity, and resistance in the circuit. These measurements can help pinpoint the location of the electrical fault.
Wiring Diagram: A wiring diagram is a schematic that shows the electrical connections of the mirror circuit. This diagram is essential for troubleshooting the circuit and identifying the various components. Wiring diagrams can be found in the vehicle's service manual or online.
Repair Procedure: Visual Inspection: A thorough visual inspection of the wiring, connectors, and switch can often reveal obvious damage, such as broken wires, corroded connectors, or a damaged switch. This is often the first step in the diagnostic process.
Repair Procedure: Switch Testing: The switch can be tested using a multimeter to ensure that it is functioning correctly. The multimeter can be used to check the continuity of the switch in the "up" position. If the switch is not working correctly, it should be replaced.
Repair Procedure: Motor Testing: The motor can be tested by applying power directly to it to see if it operates. If the motor does not operate, it is likely faulty and needs to be replaced. However, be careful not to apply excessive voltage to the motor, as this could damage it.
Repair Procedure: Wiring Continuity Testing: Continuity testing involves using a multimeter to check the continuity of the wiring harness. This can help identify broken or shorted wires. If a wire is broken, it should be repaired or replaced.
Repair Procedure: Voltage Drop Testing: Voltage drop testing involves measuring the voltage drop across the circuit to identify high resistance areas. High resistance can impede the flow of electricity and cause the B2140 code. If a high resistance area is found, it should be repaired.
Repair Procedure: Component Replacement: Once the faulty component has been identified, it should be replaced. This could be the switch, the motor, or the control module. Ensure that the replacement component is compatible with the vehicle.
Related DTCs: Other mirror-related DTCs may be present, providing further clues about the problem. For example, a DTC related to the mirror down function could indicate a problem with the power mirror control module or a wiring harness issue affecting multiple circuits.
Frequently Asked Questions
What does the B2140 code mean? The B2140 code indicates a malfunction in the "Up" control circuit of your vehicle's power mirror. This usually means the mirror won't move upwards when the switch is activated.
Can I fix the B2140 code myself? Yes, depending on your mechanical skills. Start with a visual inspection and basic troubleshooting like checking the fuse and switch. More complex repairs may require a professional.
What are the most common causes of the B2140 code? The most common causes are a faulty mirror up control switch, damaged wiring, or a failing mirror motor.
How much does it cost to fix the B2140 code? The cost depends on the cause. A faulty switch may cost $50-$150 to replace, while a more complex issue like a faulty control module could cost several hundred dollars.
Is it safe to drive with the B2140 code? While the vehicle is drivable, a non-functional mirror can compromise visibility and safety, especially when changing lanes. It's best to address the issue as soon as possible.
Conclusion
The B2140 DTC signifies a problem with the mirror's upward movement, often stemming from switch, motor, wiring, or module issues. Thorough diagnostics and repair are crucial for restoring full mirror functionality and ensuring safe driving conditions.