B3397 – Left Rear Window Up Switch Circuit Low

B3397 means the left rear window up switch circuit is reading lower than expected by the vehicle’s body control electronics. Most often, the first thing you’ll notice is the left rear window won’t roll up when the UP switch is pressed, or it works intermittently.

System: Body | Standard: ISO/SAE Controlled | Fault type: Circuit Low

Definition source: SAE J2012 naming/structure guidance (verify exact wording against your official DTC dataset)

DTC: B3397 (ISO/SAE Controlled, Body). Fault type: Circuit Low. The control module is detecting a low signal on the left rear window UP switch circuit; start with the left rear door switch area, connectors, and the door-jamb wiring where the harness flexes.

What Does B3397 Mean?

Official meaning: B3397 – Left Rear Window Up Switch Circuit Low. This code sets when the module that monitors the power window switch inputs detects the left rear window UP switch circuit signal is below the expected level. In plain terms, the vehicle is not seeing a valid “UP” request on that circuit because the input is staying low or being pulled low compared to what the module expects during normal operation.

Because the meaning is strictly a circuit low condition, B3397 indicates an electrical input problem (signal level) rather than proving the window motor is bad or that the glass is jammed. The fault can be caused by wiring, terminal fit, moisture, a switch that is not producing the correct input level, or (less commonly) a module input issue.

Theory of Operation

In a typical body electrical architecture, the left rear window switch (and/or the driver master switch) provides an UP request to a body/door control module through a dedicated circuit. When the UP switch is pressed, the circuit’s voltage or resistance state changes in a known way, and the module interprets that change as a command to raise the window.

For B3397, the module sees the UP switch circuit in a low state when it should not be low. Depending on the design, “low” may mean the input voltage is near ground, the signal cannot rise to its expected level, or the measured state stays in the low range of a resistor-ladder/multiplexed input. The module may ignore the UP request, limit window operation, or store the code for diagnostic tracking. The key point is that the monitored UP switch circuit is not reaching the expected signal level.

Symptoms

Symptoms of B3397 are usually limited to left rear window control behavior and may be constant or intermittent.

• Left rear window won’t go up: pressing the left rear UP switch does not raise the window
• Intermittent UP operation: the window raises sometimes but fails at other times
• Works from one switch but not another: UP may work from the driver master switch but not the left rear switch (or the reverse), depending on circuit routing
• UP command not recognized: the window may go down normally but the UP request is ignored
• Related body DTCs: additional body codes may be stored if other door inputs share power/ground/reference circuits

Common Causes

• Wiring damage in the left rear door or door-jamb harness: chafed insulation, pinched wires, or broken conductors that pull the circuit low
• Short to ground on the UP switch signal circuit: the circuit is being pulled low due to contact with ground or a grounded component
• Connector/terminal problems: corrosion, moisture, loose terminal tension, spread pins, or partially backed-out terminals at the switch or harness connectors
• Water intrusion: moisture in the switch or connector causing leakage paths that drag the signal low
• Left rear window switch issue: internal switch wear or contamination that prevents the circuit from reaching its proper UP signal level
• Module input concern (less common): a problem with the control module’s input circuitry after wiring integrity is confirmed

Diagnosis Steps

Use a scan tool that can access body codes/data, a digital multimeter, and the correct wiring diagram for the vehicle. The goal is to confirm the UP switch input stays low and then locate where the circuit is being pulled low (switch, wiring, connector, or module input).

1. Confirm the code and context: check whether B3397 is current or history and record any available event data (battery voltage, ignition state, door status).
2. Check for related body codes: note any other window/door switch circuit codes or low-voltage/body power supply codes that may affect inputs.
3. Verify the symptom: attempt to raise the left rear window using the left rear switch and the driver master switch; document what works and what does not.
4. Use data to watch the UP input: on the scan tool, monitor the left rear window UP switch input parameter (wording varies). Press/release the UP switch and see whether the input changes state.
5. Inspect the door-jamb harness: pull back the flex boot and look for rubbed-through insulation, cracked wires, or previous repairs that could cause the circuit to read low.
6. Inspect switch and connectors: check for moisture, corrosion, bent pins, heat discoloration, or loose terminal fit at the left rear switch connector and any intermediate connectors.
7. Check for a short to ground: using the wiring diagram and OEM-safe isolation steps, test the UP switch signal circuit for continuity to ground when it should not be grounded. Wiggle the harness while testing to find intermittents.
8. Check continuity and voltage behavior: verify circuit continuity between the switch and the module input and confirm the circuit can reach the expected signal level when commanded (per the wiring diagram and service information).
9. Evaluate the switch only after circuit checks: if wiring and terminals test good, test the switch function per the diagram (including any reference/feed circuits if applicable) to see whether it can produce the correct UP input state.
10. Clear and recheck: clear the code, operate the window repeatedly, and confirm whether B3397 returns and whether live input data behaves correctly.

Possible Fixes

• Repair damaged wiring in the left rear door/door-jamb harness that is pulling the UP switch circuit low
• Repair a short-to-ground condition on the left rear window UP switch signal circuit
• Clean, dry, and reseat connectors; repair/replace corroded terminals or terminals with poor tension
• Replace the left rear window switch if testing confirms it cannot produce the proper UP input level
• Address water intrusion sources affecting the switch/connector area (sealing, moisture removal, and connector service)
• Repair or replace the related control module only after verifying power/grounds and confirming the circuit and switch are not the cause

Can I Still Drive With B3397?

Usually yes. B3397 is a Body code and typically affects left rear window UP operation rather than engine or braking performance. The practical concern is convenience and safety: if the window cannot be raised, it may allow water intrusion, reduce security, or distract the driver while trying to operate the window.

How Serious Is This Code?

B3397 is generally low to moderate severity. It becomes more urgent if the window is stuck open or if there are signs of an electrical problem such as repeated fuse failures, hot connectors, or widespread intermittent door electrical issues. Because the fault type is circuit low, prioritizing inspection for chafing and moisture in the door and door-jamb area is important.

Repair Costs

Repair cost depends on whether the confirmed fault is wiring damage, terminal fit/corrosion, a failed sensor or switch, or additional diagnostic time to isolate an intermittent circuit problem.

Last updated: March 22, 2026