B1814

Wiper Rear Motor Down Relay Coil Circuit Failure

Body Chassis/Safety Wiper System 🟢 Low — Fix at next service ✅ Safe to Drive
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What This Actually Means

In plain language — no jargon

The rear wiper motor's relay coil circuit has failed, meaning the electrical switch that controls the rear wiper isn't working properly. Think of it like a light switch that's broken and won't flip on or off to control the wiper motor.

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Symptoms You May Notice

3 known symptoms for this code
Rear wiper does not operate or moves intermittently
Rear wiper stuck in one position
No clicking sound from relay when wiper switch is activated
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How Your ECU Detects This

Technical sensor logic and voltage thresholds

The ECU monitors the voltage and current draw across the rear wiper motor relay coil circuit when the driver activates the rear wiper switch. It detects an open circuit, short circuit, or abnormal resistance that prevents the relay from energizing properly to control the motor.

Voltage & Parameter Thresholds

ParameterNormal RangeFault Condition
Relay Coil Voltage 11-14.5V when activated Below 9V or no voltage detected
Relay Coil Resistance 70-100 ohms Open circuit (infinite) or shorted (<10 ohms)
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Diagnostic & DIY Fix Guide

Check these in order — from cheapest to most complex
1
Rear Wiper Relay
Locate the relay in the fuse box (consult owner's manual), remove the faulty relay, and install a new one of the same part number.
2
Wiring Harness and Connectors
Inspect all connectors at the relay, motor, and switch for corrosion, loose pins, or damaged wires, and repair or reseat connections as needed.
3
Rear Wiper Motor Assembly
If relay and wiring are intact, the motor itself may be faulty; test with a multimeter or replace the entire motor assembly.
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When to See a Professional Mechanic

Not all fault codes are safe to DIY

Code B1814 is a low-severity fault. Your vehicle is generally safe to drive to a workshop for diagnosis. However, do not ignore it indefinitely — low-severity codes often indicate developing problems that become expensive if neglected. Book a diagnostic appointment within 2–4 weeks. If you notice any additional symptoms (rough running, power loss, unusual smells), treat it as higher priority.

Safety note: OBD-II codes identify the system or circuit where a fault was detected — they do not always identify the exact failed component. A professional mechanic using live sensor data will diagnose the root cause more accurately than replacing parts based on the code alone.
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How to Clear Code B1814

What happens after you fix the fault

Once the fault is repaired, B1814 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.

The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.

✅ Safe to Clear When
  • Fault has been diagnosed and repaired
  • You want to confirm the repair worked
  • Code appeared after a sensor was cleaned
⚠️ Do Not Clear When
  • Preparing for an emissions/PUC test
  • Root cause is still undiagnosed
  • Check engine light is flashing
Emissions test note: Clearing codes resets OBD readiness monitors. Most vehicles need 50–100 km of mixed driving before monitors complete. Do not clear codes immediately before an emissions or PUC inspection.