B1814 — Wiper Rear Motor Down Relay Coil Circuit Failure #

Note: The description of code B1814 may vary depending on the vehicle manufacturer (OEM). Always refer to your service manual for the exact wording.

• B1814 — Rear Wiper Relay Coil Circuit Malfunction (Toyota, Lexus, Scion)
• B1814 — Wiper Rear Motor Down Relay Circuit Failure (Ford, Mazda)
• B1814 — Rear Wiper Relay Circuit Fault (Honda, Acura)
• B1814 — Rear Window Wiper Relay Error (Nissan, Infiniti)

Summary of Code B1814 #

Code B1814 is a Body Control Module (BCM)-related Diagnostic Trouble Code (DTC) that indicates a problem within the rear wiper motor down relay coil circuit. This circuit is responsible for controlling the electrical current to the rear wiper motor when it is supposed to move in the “down” or “park” position. When the BCM detects an abnormal voltage, open, or short in this specific section, it triggers the B1814 code. While this code does not affect engine performance, it can impact rear visibility and safety, especially in adverse weather. Understanding and resolving this code ensures your wiper system operates reliably as designed by the OEM.

Common Symptoms for Code B1814 #

When code B1814 is present, drivers may notice clear signs pointing to the rear wiper system. Symptoms are often straightforward, but sometimes intermittent, making diagnosis a bit like chasing shadows on a cloudy day. Here’s what you might experience:

• Rear wiper does not function or move to the park/down position
• Rear wiper moves erratically or gets stuck mid-sweep
• Intermittent operation of the rear wiper
• Clicking or buzzing sounds from the rear hatch area when activating the wiper
• Warning lights or messages on the dashboard referencing “Rear Wiper” or “Body Electrical”

Probable Causes for Code B1814 #

The B1814 code typically arises due to electrical interruptions or failures within the rear wiper relay coil circuit. Some causes are more common than others, but all should be considered for an accurate diagnosis. Here they are, listed in order of likelihood:

1. Faulty rear wiper relay (down/park relay coil malfunction or open circuit)
2. Broken, corroded, or disconnected wiring/connectors in the rear wiper relay circuit
3. Defective rear wiper motor (internal short/open affecting relay control)
4. Failed Body Control Module (BCM) or related control unit
5. Blown fuse specific to the rear wiper motor or relay

Step-by-Step Diagnosis for Code B1814 #

Diagnosing B1814 requires a methodical approach to pinpoint the cause without replacing unnecessary parts. Think of this as a detective’s checklist for the rear wiper system:

• Use an OBD-II/EOBD scanner to confirm the presence and history of B1814. Clear the code and see if it returns after operating the rear wiper.
• Inspect the rear wiper relay: locate it using the vehicle’s wiring diagram, listen for a clicking sound when the wiper is activated, and test the relay’s coil for continuity using a multimeter.
• Check the wiring and connectors between the BCM, relay, and rear wiper motor for corrosion, damage, or loose connections. Pay special attention to areas exposed to moisture.
• Test the rear wiper motor’s functionality by providing direct battery voltage and observing its response. If it fails to operate, internal faults may be present.
• Examine the relevant fuse for the rear wiper circuit. Replace if blown, but also investigate why it failed.
• If all hardware tests good, evaluate the BCM’s output using a scan tool with bi-directional controls or by measuring voltage at the relay control pin.

Possible Repairs for Code B1814 #

Repairing B1814 depends on what you discover in diagnosis. Addressing the root cause, rather than just symptoms, ensures a lasting fix. Consider these targeted repairs:

• Replace the faulty rear wiper relay if it fails continuity or function tests.
• Repair or replace damaged wiring, corroded terminals, or loose connectors in the rear wiper relay circuit.
• Replace the rear wiper motor if it is internally shorted, open, or unresponsive.
• Replace the blown fuse and correct any underlying issues causing it to blow.
• If the BCM is not providing correct outputs and all other components test good, consider BCM repair or replacement (after confirming with OEM procedures).

Is It Safe to Drive with Code B1814? #

Yes, but with limitations: Driving with code B1814 is typically safe as it does not impact the engine, brakes, or steering. However, your rear visibility is compromised in rain, snow, or dusty conditions. If you rely on the rear wiper for safety—like during adverse weather—it’s important to fix this issue before your next drive in challenging conditions. For most vehicles, this is not an immediate immobilizer, but it should not be ignored for long.

Vehicles Most Affected by Code B1814 #

B1814 is found across a variety of vehicles, especially those from manufacturers that use similar rear wiper relay designs. While not exclusive, these models see it most often:

• Toyota RAV4, Highlander, Sienna (Toyota/Lexus/Scion family)
• Ford Escape, Explorer, Edge (Ford/Mazda siblings)
• Honda CR-V, Pilot, Odyssey (Honda/Acura)
• Nissan Rogue, Murano, Pathfinder (Nissan/Infiniti)
• Hyundai Santa Fe, Kia Sorento (Hyundai/Kia)

Common Mistakes & Best Practices for Code B1814 #

Even experienced technicians can stumble when tackling B1814. Avoiding these pitfalls can save time and money, and ensure a professional repair:

• Replacing the rear wiper motor without testing the relay or wiring—often, the problem is with the relay or a corroded connector, not the motor itself.
• Overlooking the effects of water intrusion in hatchback wiring looms—moisture is a frequent culprit.
• Not checking fuse integrity or ignoring a blown fuse’s root cause.
• Neglecting to clear the code and test the system after repairs—this confirms the problem is actually resolved.
• Rushing to replace the BCM without following full OEM diagnostic flowcharts.

Express FAQ for Code B1814 #

Q: Can I fix B1814 myself without special tools?
A: Basic steps like checking fuses and connectors can be done with a multimeter and patience. However, advanced diagnosis may require a scan tool and wiring diagrams. If in doubt, consult a professional.

Q: Will B1814 clear itself after repairs?
A: Often, yes—once the fault is corrected and the system is reset with a scan tool, the code should not return. If it does, double-check your work or look for intermittent wiring faults.