B2324 – Left rear door motor electronic control unit (ECU) communication stop (Toyota)

B2324 means your Toyota has detected a communication loss with the left rear door motor electronic control unit (ECU). For most owners, the real-world effect is that the left rear door’s powered function may stop working, work only sometimes, or behave inconsistently, even though the rest of the vehicle drives normally. On a 2010 Toyota Prius, this code is manufacturer-specific (Toyota-controlled), so the scan tool’s description is the correct definition to use. Technically, it indicates the networked data exchange to the left rear door motor ECU has stopped, which can be caused by power/ground issues, wiring/connectors, or a fault in the door ECU itself.

B2324 Quick Answer

On Toyota vehicles, B2324 points to a stopped communication condition involving the left rear door motor ECU. Start by confirming the ECU is present on the scan tool network list, then check door-area power/ground and connector/wiring integrity before replacing any modules.

What Does B2324 Mean?

B2324 means the car can’t reliably “talk” to the left rear door motor ECU, so the left rear door motor system may not respond as expected. In technical terms on Toyota platforms, this is a body-system communication-loss DTC indicating the left rear door motor ECU’s communication has stopped (lost messages, no response to diagnostic requests, or intermittent network participation, depending on the platform and scan tool).

Theory of Operation

On Toyota vehicles, door motor functions that use an electronic control unit typically rely on a body network so the door ECU can exchange status and commands with a master body controller (often part of a body ECU, multiplex network controller, or related body-domain module depending on the platform). The left rear door motor ECU reports its presence, status, and sometimes motor position/operation feedback over the network, and it may also receive requests to run the motor or to enable/disable functions based on vehicle state.

B2324 sets when the expected communication with the left rear door motor ECU stops. Toyota’s logic can vary by model/platform, but the diagnostic direction is consistent: either the door ECU is not powered/grounded correctly, the network path between modules is disrupted (wiring/connectors, especially through the door jamb), or the ECU is powered but not participating on the network due to an internal fault or related network issue.

Symptoms

Drivers and technicians may notice one or more of the following when B2324 is present:

• Scan tool shows the left rear door motor ECU as not responding, missing from the ECU list, or intermittently dropping offline during a health check
• Left rear door function powered operation for the left rear door motor system is inoperative or intermittent
• Intermittent operation the issue changes with door movement (opening/closing) or bumps, suggesting a wiring/connector sensitivity
• Body electrical oddities related body features near the left rear door may act inconsistent if they share a harness/ground path
• No warning light many body communication DTCs do not illuminate a prominent dash warning, even though a code is stored
• Stored history code B2324 may be logged as a past/current code after low battery events or service work involving the door harness

Common Causes

• Open circuit, short to ground, or short to power in the communication lines between the Toyota body network and the left rear door motor ECU
• Loss of power supply to the left rear door motor ECU (blown fuse, poor power distribution feed, or internal power interruption)
• High resistance or intermittent ground connection for the left rear door motor ECU causing module resets and communication dropouts
• Connector issues at the left rear door area (loose fit, backed-out terminals, corrosion, moisture intrusion, or terminal spread)
• Harness damage in the door jamb flex point (repeated opening/closing causing broken conductors or intermittent contact)
• Fault within the left rear door motor ECU itself (internal failure leading to “no response” on the network)
• Network wiring fault affecting multiple nodes on the same Toyota body communication branch (shared splice, joint connector, or localized harness segment issue)
• Improper prior repair or accessory installation impacting the door harness (pinched wiring, poor splices, incorrect terminal repairs)

Diagnosis Steps

Tools recommended: a scan tool capable of Toyota body network health checks and ECU identification, a digital multimeter, and basic back-probing/terminal test tools. If available, use a wiring diagram and connector views for the Prius body system to avoid mis-pinning. A test light or load tool is helpful to verify power/ground integrity under load without relying on unloaded voltage readings.

1. Confirm the DTC and capture data: Using a Toyota-capable scan tool, confirm B2324 is present and record freeze frame/snapshot data and all stored/pending codes from Body-related ECUs. Note whether the code is current or history, and whether other communication-related DTCs are stored that could indicate a broader network or power issue.
2. Check power distribution first and verify ECU presence on a network scan: Before probing the left rear door motor ECU connector, check related fuses and power feeds for the body/door system per vehicle service information. Then run a network scan (health check) and confirm whether the scan tool can “see” or identify the left rear door motor ECU. If the ECU does not appear on the scan, prioritize power/ground and network branch integrity checks over component replacement.
3. Verify ECU power and ground under load: At the left rear door motor ECU connector, verify power supply and ground integrity while the circuit is loaded (for example, with the system commanded ON where applicable). Do not rely on continuity alone; check for voltage drop or evidence of an intermittent supply/ground that could cause the ECU to reboot and drop communication.
4. Inspect connectors and harness routing (door and body side): Perform a careful visual and physical inspection of the left rear door ECU connector, terminals, and harness routing. Pay special attention to the door jamb boot/flex area, where conductor breaks and intermittent opens are common. Look for moisture, corrosion, fretting, terminal push-outs, and signs of prior repairs.
5. Wiggle test for intermittent communication loss: With ignition ON and the scan tool connected, monitor network status for the left rear door motor ECU (or related data list items) while gently moving the harness at the door jamb, near connectors, and near any splices/joint connectors. If communication drops in/out, isolate the segment that triggers the fault and inspect for broken conductors or poor terminal tension.
6. Check communication line integrity with ignition ON: If service information indicates dedicated communication lines to the left rear door motor ECU, test the communication circuit for shorts to ground/power and for opens. For any voltage-level checks on the communication lines, measure with ignition ON because network bias voltage is only present when the circuit is powered; ignition-OFF readings are not a valid reference. Compare left rear door circuit behavior to a known-good door/module circuit when possible (same test method, same conditions).
7. Isolate the ECU vs. wiring (module unplug test where appropriate): If the left rear door motor ECU is not detected on the scan tool, unplug the ECU and re-check the network behavior as directed by Toyota service information. A shorted module or shorted branch wiring can disturb communication; isolation testing can help determine whether the network recovers when the ECU/branch is disconnected. Reconnect and confirm whether the fault returns.
8. Functional checks of door operation and commands: Command door lock/unlock (and other applicable left rear door functions) using the scan tool active tests if available. Confirm whether the ECU responds, whether the actuator moves, and whether status inputs change plausibly. Lack of response together with a “communication stop” points back to power/ground, wiring integrity, or an internal ECU fault rather than a simple mechanical issue.
9. Repair as indicated and confirm the fix: Repair wiring, terminals, grounds, or power feeds found defective. Clear DTCs, cycle ignition, and re-run the Toyota network scan. Confirm the left rear door motor ECU is consistently identified and that B2324 does not reset during an extended wiggle test and repeated door operations.
10. Final verification under real conditions: Road test or operate the vehicle through typical conditions that previously triggered the code (door usage, lock/unlock cycles, temperature/moisture exposure if relevant). Recheck for pending/history DTCs and confirm consistent communication with the left rear door motor ECU.

Professional tip: For Toyota “communication stop” body codes, avoid replacing the door actuator/ECU assembly until you have proven stable power and ground at the ECU under load and confirmed the network branch to that door is healthy. The door-jamb flex harness is a frequent intermittent failure point; a clean-looking harness can still have broken conductors inside the insulation, so combine scan-tool monitoring with a controlled wiggle test to pinpoint the break.

Possible Fixes

• Repair or replace damaged wiring in the left rear door harness, especially at the door jamb/flex boot area
• Clean, tighten, or repair ECU connector terminals (address corrosion, terminal spread, backed-out pins, and moisture intrusion)
• Restore proper power/ground to the left rear door motor ECU (repair feeds/grounds, replace related fuse only after correcting the root cause)
• Repair communication line faults (open/short) in the affected body network branch, including any compromised splice/joint connector sections
• Replace the left rear door motor ECU/actuator assembly only after confirming wiring, power/ground, and network integrity are correct and the ECU still does not communicate
• Correct improper prior wiring repairs or accessory-related wiring issues affecting the left rear door circuit

Can I Still Drive With B2324?

On Toyota vehicles, DTC B2324 indicates a Left rear door motor electronic control unit (ECU) communication stop. In many cases, the vehicle remains drivable because this is a Body-network issue rather than an engine or braking fault. However, you should expect reduced or inconsistent operation of left rear door-related functions controlled by that door motor ECU (for example, power door lock/unlock behavior for that door, window/door motor features, or related convenience functions, depending on Prius configuration). Treat it as a “driveable but needs attention” fault: if the concern includes a door that won’t latch/lock reliably, a child safety concern, or intermittent electrical behavior that suggests a wiring short, avoid carrying passengers in that seating position until the fault is corrected and the code no longer returns.

How Serious Is This Code?

B2324 is usually moderate in severity. Most of the time it is an inconvenience (loss of a specific door function or intermittent door control behavior) rather than an immediate drivability problem, since the code’s official definition points to a communication stop with a door motor ECU in the Body system. It becomes more serious when the communication loss is caused by a wiring fault that can spread symptoms to other Body network nodes (multiple Body DTCs, repeated network dropouts), or when the failed door function creates a practical safety issue (door won’t lock, window won’t respond, or the door module cycles unexpectedly). If B2324 appears alongside widespread communication codes or the Prius shows multiple interior electrical glitches, prioritize diagnosis promptly to prevent battery drain, repeated wake-ups, or escalating network instability.

Common Misdiagnoses

Technicians commonly misdiagnose B2324 by replacing the left rear door motor ECU immediately, assuming the module is “dead,” without first proving the communication stop is internal to the ECU rather than caused by power/ground loss, connector damage, or network line issues. Another frequent mistake is chasing the symptom (a slow window, an inoperative lock) and replacing the motor/regulator assembly without confirming the scan tool’s network status and whether the ECU is present on the network. Water intrusion and door-jamb harness fatigue are often overlooked; if the communication drops only when the door moves, it points more strongly to harness/connector faults than to a module failure. Avoid wasted spending by verifying: consistent ECU power and ground under load, stable network integrity at the ECU connector, and whether other Body modules report related communication DTCs that suggest a shared network problem.

Most Likely Fix

The most frequently confirmed repair directions for a Toyota B2324 “communication stop” are (1) repairing wiring/connector faults between the Body network and the left rear door motor ECU (especially at the door-jamb harness, terminals, or corrosion/water intrusion points) and (2) restoring proper ECU power/ground by correcting blown fuses, poor grounds, or high-resistance connections that cause the ECU to drop offline intermittently. Only after those checks support it should a left rear door motor ECU be considered suspect. If module replacement is required, Toyota-specific initialization or configuration may be needed, and verification with a Toyota-compatible scan tool is typically part of a complete repair.

Repair Costs

Network and communication fault repairs vary by root cause — wiring/connectors are often the source, but module-level repairs or replacements can be significantly more expensive.

Last updated: March 28, 2026