The B3397 diagnostic trouble code (DTC) indicates a problem within the electrical circuit controlling the "Up" function of the left rear window switch. This code suggests that the vehicle's computer (ECU/PCM) has detected a lower-than-expected voltage signal coming from the switch circuit when the "Up" command is activated. Addressing this issue promptly is crucial for restoring full functionality to the left rear window and preventing further electrical complications.

This code doesn't necessarily mean the switch itself is faulty, but rather pinpoints a potential problem within the electrical circuit connecting the switch to the window motor and the vehicle's computer. Therefore, a thorough diagnostic process is required to pinpoint the root cause of the problem.

B3397: Key Information

Area Description Possible Causes
Definition Left Rear Window Up Switch Circuit Low: Indicates the ECU has detected a voltage lower than expected in the circuit when the left rear window up switch is activated. The ECU expects a certain voltage level when the switch is pressed, and a deviation from this expected level triggers the code. Faulty Left Rear Window Switch
 Open or Shorted Wiring in the Circuit
Poor Electrical Connections (corrosion, loose terminals)
 Faulty Window Motor
Faulty Body Control Module (BCM) (less common)
 Low Battery Voltage
* Faulty Driver Door Master Switch (depending on vehicle configuration)
Symptoms Left Rear Window Not Operating (or operating intermittently) when using the left rear door switch.
 Left Rear Window Operating Normally from the Driver's Master Switch (if equipped).
Check Engine Light (CEL) or Window System Warning Light illuminated.
 Other Window Malfunctions (rare, but possible if related circuits are affected).
* Inability to clear the B3397 code.
Diagnostic Steps 1. Visually Inspect Wiring and Connectors
2. Test the Window Switch
3. Check for Voltage at the Switch Connector
4. Check for Ground at the Switch Connector
5. Test the Wiring for Continuity and Shorts
6. Test the Window Motor
7. Check Battery Voltage
8. Inspect the Driver Door Master Switch (if applicable)
9. Consult Vehicle-Specific Wiring Diagrams
10. Scan for other relevant DTCs
11. Check the BCM (Body Control Module) last.

Detailed Explanations

Definition: The B3397 code specifically points to a low voltage condition within the circuit responsible for raising the left rear window when the switch on the left rear door itself is used. It's important to note that the issue might not be present when using the master window control on the driver's door, depending on the vehicle's wiring configuration. The ECU monitors the voltage signal from the switch and compares it to an expected value. A voltage significantly lower than expected triggers this DTC.

Symptoms: The most obvious symptom is the inability to raise the left rear window using the switch on the left rear door. However, the window might still operate correctly from the driver's master control. The check engine light might illuminate, or a specific window system warning light could appear on the dashboard. Intermittent operation, where the window sometimes works and sometimes doesn't, is also a possible symptom. In rare cases, if the faulty circuit is impacting other related circuits, other window malfunctions might occur.

Possible Causes:

  • Faulty Left Rear Window Switch: The switch itself could be defective, failing to provide the correct voltage signal when activated. Internal corrosion or mechanical wear can cause this.

  • Open or Shorted Wiring in the Circuit: Damaged wiring, either an open circuit (broken wire) or a short circuit (wire touching ground or another wire), can disrupt the voltage signal. This is a very common cause.

  • Poor Electrical Connections (corrosion, loose terminals): Corrosion on connectors or loose terminals can increase resistance in the circuit, leading to a voltage drop. These are often found in areas exposed to moisture or temperature fluctuations.

  • Faulty Window Motor: While less likely, a faulty window motor can draw excessive current, potentially causing a voltage drop in the switch circuit, especially if the motor is struggling to operate.

  • Faulty Body Control Module (BCM) (less common): The BCM controls various electrical functions in the vehicle, including the power windows. A malfunctioning BCM can sometimes cause window control issues, but this is less frequent than other causes.

  • Low Battery Voltage: Insufficient battery voltage can affect the entire electrical system, including the window circuits. This is more likely to be a contributing factor if other electrical components are also malfunctioning.

  • Faulty Driver Door Master Switch (depending on vehicle configuration): In some vehicles, the driver's master switch can influence the operation of individual window switches. A fault in the master switch could indirectly affect the left rear window circuit.

Diagnostic Steps:

  1. Visually Inspect Wiring and Connectors: Begin by carefully inspecting the wiring and connectors associated with the left rear window switch. Look for any signs of damage, corrosion, or loose connections. Pay close attention to the wiring harness that runs between the door and the vehicle body, as this area is prone to wear and tear.

  2. Test the Window Switch: Use a multimeter to test the window switch for proper operation. Check for continuity between the terminals when the switch is in the "Up" position. Refer to the vehicle's wiring diagram to identify the correct terminals to test. A reading of infinite resistance indicates a faulty switch.

  3. Check for Voltage at the Switch Connector: With the ignition on, use a multimeter to check for voltage at the switch connector. You should find a voltage reading close to battery voltage on the power supply wire. If there is no voltage, there is likely a problem with the power supply circuit.

  4. Check for Ground at the Switch Connector: Use a multimeter to check for a good ground connection at the switch connector. There should be close to 0 ohms resistance between the ground terminal and the vehicle's chassis ground.

  5. Test the Wiring for Continuity and Shorts: Use a multimeter to test the wiring between the switch connector and the window motor for continuity. There should be low resistance between the terminals. Also, check for shorts to ground by measuring the resistance between each wire and the vehicle's chassis ground. There should be infinite resistance.

  6. Test the Window Motor: Apply power and ground directly to the window motor to see if it operates. If the motor does not operate, it is likely faulty.

  7. Check Battery Voltage: Ensure the battery voltage is within the specified range (typically 12.6 volts or higher with the engine off). Low battery voltage can cause various electrical problems, including window malfunctions.

  8. Inspect the Driver Door Master Switch (if applicable): If the vehicle's wiring configuration allows, inspect the driver's master window switch for any signs of damage or malfunction. Try operating the left rear window from the master switch to see if it works. If it does, this suggests the problem is isolated to the left rear door switch or its wiring.

  9. Consult Vehicle-Specific Wiring Diagrams: Obtain the vehicle's specific wiring diagrams for the power window system. These diagrams will provide valuable information about the wiring layout, connector locations, and component identification.

  10. Scan for other relevant DTCs: Use an OBD-II scanner to check for any other diagnostic trouble codes that might be related to the power window system.

  11. Check the BCM (Body Control Module) last: After all other possible causes have been ruled out, consider the possibility of a faulty BCM. This usually requires professional diagnostics and programming.

Frequently Asked Questions

What does the B3397 code mean? It indicates a low voltage signal in the "Up" circuit of the left rear window switch, as detected by the vehicle's computer.

Can I fix this problem myself? Yes, with proper tools, knowledge, and following the diagnostic steps, you might be able to identify and fix the issue. However, if you're not comfortable with electrical troubleshooting, it's best to consult a professional.

What tools do I need to diagnose this code? You'll need a multimeter, OBD-II scanner, wiring diagrams for your vehicle, and basic hand tools.

Could a blown fuse cause this code? A blown fuse is possible, but it's more likely to disable the window entirely rather than specifically causing a "circuit low" code. Check the fuse related to the power windows.

How much will it cost to fix this problem? The cost can vary greatly depending on the cause. A simple wiring repair might be inexpensive, while replacing a faulty BCM can be significantly more costly.

Conclusion

The B3397 code indicates a problem within the left rear window's "Up" switch circuit, generally related to wiring, connections, or the switch itself. A systematic diagnostic approach, starting with visual inspection and progressing to component testing, is key to accurately identifying and resolving the issue, restoring full functionality to the left rear window.