B2226 – Left rear window motor circuit open (BYD)

B2226 means the left rear power window may stop working or work only sometimes. You will usually notice the left rear window will not move from the switch. According to BYD factory diagnostic data, this code indicates an open circuit in the left rear window motor circuit. “Circuit open” matters because the module cannot push current through the motor path. The motor will not run even if the switch works. This DTC points to a suspected trouble area. It does not prove the motor has failed.

B2226 Quick Answer

On BYD vehicles, B2226 points to an open circuit in the left rear window motor circuit. Focus first on wiring, connectors, and power/ground delivery to the motor under load.

What Does B2226 Mean?

Official definition: “Left rear window motor circuit open.” In plain terms, the BYD body system sees a command to move the left rear window, but the motor circuit does not complete. The real-world result is a left rear window that will not raise or lower, or that works intermittently.

What the module is checking: the window control electronics monitor motor circuit continuity and electrical response when the system commands movement. The controller expects to see current flow and a valid voltage change at the motor outputs. Why it matters: an “open” usually comes from a broken wire, a backed-out terminal, corrosion, or a failed internal connection in the motor or harness. Diagnose the circuit first before replacing the regulator or motor.

Theory of Operation

On BYD platforms, the body electrical system controls the left rear window through a window switch input and a power output stage. The controller drives the motor in one direction for “up” and reverses polarity for “down.” The system also watches for pinch protection and stall conditions by monitoring electrical load.

B2226 sets when the controller commands motor operation but cannot see the expected circuit response. An open in either motor feed, motor ground path, or connector can prevent current flow. A damaged door-jamb harness often creates an intermittent open. A high-resistance connection can behave like an open when the motor loads up.

Symptoms

You will usually see one or more of these symptoms with B2226 on a BYD vehicle:

• Window inoperative left rear window will not move from the driver or rear switch
• Intermittent operation window works only when the door moves or when you press the switch repeatedly
• No motor sound you hear no motor noise during an up or down command
• One-direction failure window moves in one direction but not the other on some faults
• Auto function disabled one-touch up or down stops working for that window
• Pinch protection behavior window may stop early or reverse due to unstable electrical feedback
• Related body DTCs additional window or door electrical codes may store if the harness has multiple breaks

Common Causes

• Open in the motor feed or motor return wire: A broken conductor stops current flow, so the BYD body controller sees no motor circuit continuity during a command.
• High-resistance in the door-to-body harness boot: Repeated flexing at the rear door hinge area raises resistance until the controller interprets the circuit as effectively open.
• Loose, backed-out, or corroded window motor connector terminals: Poor terminal tension or corrosion prevents the motor from drawing current when the module commands movement.
• Failed power window fuse or upstream power distribution issue: Loss of B+ supply to the window system leaves the left rear motor circuit without power, which presents as an open during self-checks.
• Fault in the left rear window switch or switch signal path: A missing or implausible command input can stop the controller from driving the motor and trigger open-circuit logic on some BYD platforms.
• Motor internal open (brushes/commutator/thermal protector): An internal break inside the motor prevents current draw even with correct power and ground at the connector.
• Water intrusion in the left rear door module area or connectors: Moisture attacks terminals and splices, creating an intermittent open that often appears after rain or washing.
• Body controller or door module driver fault: A failed output stage can leave the motor undriven, and the module then flags the circuit as open after it commands operation.

Diagnosis Steps

You need a scan tool that can access BYD body/door modules and read freeze frame or event data. Use a DVOM with min/max capture, plus a fused jumper or a test light for loaded checks. Have basic trim tools to access the left rear door switch and motor connector. Perform voltage-drop tests with the circuit operating.

1. Confirm B2226 in the BYD scan tool report and note whether it shows as pending or stored/confirmed. Record freeze frame or event data tied to the fault. For this circuit/open code, focus on battery voltage, ignition state, window command status, and any related door or body DTCs. Freeze frame shows conditions when the fault set, while a scan tool snapshot helps catch an intermittent open during an active wiggle test.
2. Inspect the easiest physical items before meter work. Check the left rear window for binding and verify the glass moves freely in the run channels. Then inspect visible wiring at the left rear door hinge area and the rubber boot between the body and door for pinched, cut, or stretched wires.
3. Check fuses and power distribution that feed the power window system. Verify the correct fuse(s) do not just look good. Load-test them with the circuit commanded on, or measure for voltage drop across the fuse while commanding the left rear window. A fuse can pass a visual check and still fail under load due to heat damage.
4. Verify module power and ground integrity under load. Back-probe the relevant body/door module power and ground circuits if service information identifies them. Run the window command and perform voltage-drop testing on the ground path. Keep ground drop under 0.1V with the circuit operating, because a weak ground can mimic an open motor circuit.
5. Use the scan tool to command the left rear window motor up and down, if bidirectional control exists on your BYD platform. Listen for relay clicks or driver activation in the door. Watch for live data items such as window switch input status, command state, and any reported motor current or position feedback if available.
6. Access the left rear door trim and inspect the window motor connector and switch connector. Look for backed-out terminals, spread pins, corrosion, or signs of water tracks. Perform a gentle pin-drag test on terminals where possible. Repair terminal fit issues before condemning any component.
7. Check for power and ground at the window motor connector while commanding movement. Use a DVOM and capture min/max to catch brief drops. If the system uses polarity reversal, you should see the polarity change between up and down commands. If you see no change, the issue sits upstream in wiring, connectors, or the module output.
8. If power/ground reach the connector but the motor does not run, load-test the circuit at the connector. Use a test light or a suitable load device across the motor feed and return while commanding the window. A weak feed or ground can show correct voltage unloaded but collapse under load. Use voltage-drop testing on both sides to find the high-resistance point.
9. If the connector shows correct loaded power and ground during a command, verify the motor itself. Disconnect the motor and check for an internal open with resistance testing as a quick screen, then confirm with a controlled fused jumper test only if safe and accessible. If the motor runs on a direct fused feed but not on the vehicle harness, the harness or module control stays suspect.
10. Focus on the door-to-body harness if results point upstream. Perform a wiggle test at the hinge boot while commanding the motor and watching live data and meter readings. Intermittent opens often appear only when the harness flexes. If the fault appears, isolate the exact conductor and repair it with proper splicing and strain relief.
11. After repairs, clear DTCs and rerun the window through multiple full up/down cycles. Recheck for pending codes and confirm the code does not reset on key-on. For continuously monitored circuits, a hard open typically returns immediately. If it stays clear, complete a short drive and re-scan all related body/door modules to confirm no secondary faults remain.

Professional tip: Do not trust continuity checks alone on BYD door harness problems. A wire can pass continuity with a few strands intact. That same wire fails under motor load and sets B2226. Use voltage-drop under load at the motor connector and at the module output. That method pinpoints the exact side of the circuit that opens.

Possible Fixes

• Repair an open or high-resistance wire in the left rear door harness: Splice and seal the damaged conductor, then add strain relief at the hinge area.
• Clean/repair terminals at the window motor or switch connectors: Correct pin fit, remove corrosion, and restore terminal tension as needed.
• Replace a failed fuse or correct the upstream power feed fault: Restore proper power distribution to the window circuit, then verify loaded voltage at the door.
• Replace the left rear window motor only after circuit tests pass: Confirm proper loaded power and ground at the connector before installing a motor.
• Repair water intrusion sources in the left rear door: Correct sealing issues and clean affected connectors to prevent repeat opens.
• Repair or replace the responsible BYD body/door module only after output testing: Verify the module commands do not produce a driven output despite correct inputs and power/ground integrity.

Can I Still Drive With B2226?

You can usually drive your BYD with B2226 because it targets the left rear window motor circuit. It does not affect propulsion, braking, or steering. Treat it as a body electrical fault with comfort and security impact. Do not force the switch if the window stalls. Repeated commands can overheat the motor, switch contacts, or wiring. Avoid automatic window functions until you fix it. If the window stuck open, address it quickly to prevent water intrusion, theft risk, and interior damage. If the window stuck closed, plan repairs soon so you can exit safely in an emergency.

How Serious Is This Code?

B2226 ranges from an inconvenience to a real ownership problem. When the window still moves sometimes, the fault often comes from an intermittent open at the door jamb harness or a loose connector. That situation usually causes no immediate safety risk. When the window stays open, severity rises fast due to weather exposure and visibility issues. A stuck window can also defeat child safety expectations in the rear. This code still points to a suspected circuit area, not a failed motor. Confirm power, ground, and control integrity under load before you replace parts.

Common Misdiagnoses

Technicians often replace the left rear window motor first because the scan text mentions “motor circuit.” That wastes time when the actual problem sits in the hinge-area harness where wires flex. Another common miss involves testing the circuit with a meter unloaded. An open can “look good” until the motor draws current. Some also blame the switch without checking if the door module or body controller loses feedback from the motor circuit. Finally, many clear the code and call it fixed. They never cycle the window through full travel to prove the open does not return.

Most Likely Fix

The most common confirmed repair direction for B2226 on BYD vehicles involves restoring continuity in the left rear window motor feed, ground, or control path. Start with a tight visual and tug inspection at the left rear door connector and the door jamb boot. Repair broken conductors, backed-out terminals, or corrosion, then retest window operation under load. If wiring integrity checks out, validate the switch and door control outputs with live data and bidirectional commands. Only then consider a motor or door module fault, since the code does not prove a failed component.

Repair Costs

Repair cost depends on whether the confirmed root cause is a sensor, wiring, connector issue, or control module problem. Verify the fault electrically before replacing parts.

Last updated: March 30, 2026