B1814 — Wiper Rear Motor Down Relay Coil Circuit Failure

B1814 — Wiper Rear Motor Down Relay Coil Circuit Failure. A fault in the ignition system. Short, gentle driving to a shop is usually possible. Typical causes: failed ignition coil or coil pack, faulty ignition control circuit in the ECM, worn spark plugs or wrong plug gap.

body electrical

Is it safe to drive?

Drive with caution Drive with caution and avoid load. Ignition faults cause misfires that quickly overheat and destroy the catalytic converter; if the Check Engine Light flashes, stop and fix it first.

How to diagnose with an OBD scanner

Read the code and freeze frame Connect an OBD2 scanner, confirm B1814 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
Check for companion codes and TSBs Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many B0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
Inspect wiring and connectors Visually inspect the wiring harness and connectors related to the ignition system for damage, corrosion, chafing or poor contact.
Subsystem check Swap the coil to another cylinder and see if the fault code follows it.
Subsystem check Inspect spark plugs for wear, oil or carbon tracks and check plug gaps.
Verify the repair Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm B1814 does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for B1814 (parts and labor, USD, independent shop rates): Replace an ignition coil: $150–$380; Repair coil wiring or connector: $80–$250; Replace spark plugs: $90–$250. Overall, fixing B1814 usually costs between $80 and $380. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Common questions

What are the symptoms of B1814?

Drivers most often notice: Check Engine Light on, loss of power and jerking, misfires under load or at idle, hard starting, especially in damp weather.

Is it safe to drive with B1814?

Drive with caution and avoid load. Ignition faults cause misfires that quickly overheat and destroy the catalytic converter; if the Check Engine Light flashes, stop and fix it first.

What does OBD2 code B1814 mean?

How much does it cost to fix B1814?

Replace an ignition coil — $150–$380; Repair coil wiring or connector — $80–$250; Replace spark plugs — $90–$250. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.

Will B1814 clear itself?

Sometimes B1814 clears after a few drive cycles if the fault was intermittent — for example a loose connector or a tank of bad fuel. The underlying cause usually remains, so the code tends to return. Clear it once; if it comes back, diagnose rather than erase it repeatedly.

The rear wiper motor circuit relies on a relay to send power to the motor when you activate the switch. The relay contains an electromagnetic coil that, when energized, pulls contacts closed to complete the high-current path to the motor. Code B1814 triggers when the powertrain or body control module detects that this coil circuit is not behaving correctly — either remaining open when it should close, or shorted when it should remain inactive. The fault must repeat under specific conditions before the module logs B1814 and illuminates the warning light.

When the module stores B1814, it also captures a freeze frame snapshot: engine load, RPM, coolant temperature, and vehicle speed at the moment the failure occurred. This data pinpoints exactly when the problem happened, which matters because you need to reproduce those conditions during testing. Without that context, you risk chasing a symptom that only appears under load or at certain speeds.

Not every rear wiper failure sets B1814. The circuit must fail in the specific way the diagnostic strategy monitors — a coil that opens or shorts in a way the module can detect. If the motor itself burns out but the relay circuit remains intact, this code typically does not appear.

Symptoms of B1814

Rear wiper fails to operate or moves sluggishly
Wiper stalls mid-stroke or does not complete the wiping arc
Check Engine Light or dedicated wiper warning indicator illuminates
Intermittent operation that worsens with temperature changes
Clicking sound from the relay area when the wiper is activated, with no motor movement
Other body electrical functions fail simultaneously if a shared ground or power feed is involved

Common Causes of B1814

Failed rear wiper relay — the coil inside the relay has opened or shorted
Damaged wiring or connector between the relay and rear wiper motor
Corrosion or moisture intrusion at the motor connector or relay socket
Blown fuse feeding the rear wiper circuit
Faulty body control module that cannot properly energize the relay coil
Short to ground or short to battery in the relay control circuit

How to Diagnose B1814

Connect an OBD2 scanner and confirm B1814 is stored. Save the freeze frame data — it records engine load, RPM, temperature, and speed when the fault occurred, giving you the exact conditions to reproduce during testing.
Check for related fault codes. Codes in the B0xxx or U0xxx range may point to a shared control issue or a problem in the module itself.
Consult manufacturer technical service bulletins for your vehicle make and model — many body electrical faults have published service procedures or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
Visually inspect the rear wiper relay, its socket, and the wiring harness running to the rear wiper motor. Look for damaged insulation, broken wires, pushed pins, or corrosion on the connector terminals.
Test the relay coil circuit with a multimeter — check for proper resistance at the relay coil terminals and verify that the control signal from the body module reaches the relay when the wiper switch is activated.
Clear the code, operate the rear wiper through a complete cycle, and verify B1814 does not return. If it recurs, the fault is confirmed and repair is needed.

Repair Options for B1814

Start with the least expensive components before replacing modules:

Replace the rear wiper relay — $50–$150 (parts and labor at independent shop rates)
Repair damaged wiring or connectors — $80–$250
Replace the rear wiper motor if the motor itself has failed — $120–$300
Body control module replacement or reprogramming — $200–$600 (rare; only if no other cause is found)

How Much Does It Cost to Fix B1814?

The total depends entirely on which part is actually at fault. Independent shop labor runs $75–$120 per hour in most markets. The most common fix is a failed relay, which typically costs $50–$150 including diagnosis and installation. If wiring repair is needed, expect $80–$250 depending on how much harness work is involved. The wiper motor itself runs $120–$300 installed. Module replacement is uncommon but can reach $200–$600 when required. An accurate diagnosis before buying parts keeps total cost predictable and prevents unnecessary component replacement.

Can You Drive with B1814?

B1814 affects the rear wiper only — it does not compromise engine operation, braking, or steering. Drive with caution in wet or low-visibility conditions where rear visibility matters. If the Check Engine Light flashes, the fault may be affecting other systems through a shared module or circuit, and you should have it diagnosed promptly. Otherwise, schedule repair at your convenience but do not ignore it before long highway trips in rain.