B1819 — Wiper Rear Motor Up Relay Coil Circuit Open

OBD2 code B1819 flags a problem with the ignition system (wiper rear motor up relay coil circuit open). Short, gentle driving to a shop is usually possible. Common culprits: faulty ignition control circuit in the ECM, failed ignition coil or coil pack, moisture or oil in the spark plug wells.

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

  1. Read the code and freeze frame Connect an OBD2 scanner, confirm B1819 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
  2. 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.
  3. Inspect wiring and connectors Visually inspect the wiring harness and connectors related to the ignition system for damage, corrosion, chafing or poor contact.
  4. Subsystem check Do a continuity test end-to-end on the wiper rear motor up relay coil circuit and wiggle the harness while measuring — intermittent opens show up as fluctuating readings.
  5. Subsystem check Swap the coil to another cylinder and see if the fault code follows it.
  6. Subsystem check Inspect spark plugs for wear, oil or carbon tracks and check plug gaps.
  7. Verify the repair Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm B1819 does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for B1819 (parts and labor, USD, independent shop rates): Replace spark plugs: $90–$250; Replace an ignition coil: $150–$380; Repair coil wiring or connector: $80–$250. Overall, fixing B1819 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 is the most common cause of B1819?

The most common causes are: faulty ignition control circuit in the ECM, failed ignition coil or coil pack, moisture or oil in the spark plug wells.

What does OBD2 code B1819 mean?

OBD2 code B1819 flags a problem with the ignition system (wiper rear motor up relay coil circuit open). Short, gentle driving to a shop is usually possible. Common culprits: faulty ignition control circuit in the ECM, failed ignition coil or coil pack, moisture or oil in the spark plug wells.

Is it safe to drive with B1819?

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 do I diagnose B1819 myself?

Start with a scan: confirm B1819, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the wiper rear motor up relay coil, and verify the suspect component against live data before buying parts.

How much does it cost to fix B1819?

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

The engine control module stores trouble code B1819 when it detects a break in the electrical path feeding the rear wiper motor's up relay coil. Put another way, the module is expecting to see a specific voltage or ground at a particular circuit, but that circuit is interrupted somewhere between the module and the relay coil. When the module cannot complete the expected current path, it logs B1819 and illuminates the Check Engine Light.

In modern vehicles, the body control module or engine control unit constantly monitors the health of circuits throughout the car. For the rear wiper circuit to function properly, each connection must be intact — the wiring harness, the connectors at both ends, the fuse that protects the circuit, and the relay coil itself. B1819 indicates that at least one of these links has failed, breaking the circuit somewhere along the path. The module typically requires multiple failed attempts across several drive cycles before it commits the code to memory. When it does, it also saves a freeze frame — a snapshot of engine rpm, load, coolant temperature, and vehicle speed captured at the exact moment the fault occurred.

Reading that freeze frame data before beginning any diagnosis is a smart first step. It tells you what conditions were present when the module first noticed the problem, which helps you reproduce the failure during testing. Many mechanics skip this step, but it often points you directly to the root cause rather than chasing symptoms.

Common symptoms of B1819

  • Rear wiper fails to activate or operate in the up direction
  • Intermittent wiper operation that comes and goes with vehicle vibration
  • Check Engine Light or dedicated body fault light illuminated on the instrument cluster
  • Loss of power under load or hesitation during acceleration
  • Rough idle or engine misfire noticeable through the steering wheel or seat
  • Hard starting, particularly in wet or humid conditions
  • Noticeable increase in fuel consumption over several fill-up cycles

What causes B1819?

  • Blown fuse protecting the rear wiper motor circuit
  • Electrical connector that is unplugged, has a backed-out terminal pin, or shows signs of corrosion
  • Broken or cut wire within the wiper motor harness, often caused by chafing against body panels
  • Internally open wiper rear motor up relay coil that no longer produces a magnetic field when energized
  • Failed ignition coil or coil pack producing weak or inconsistent spark
  • Faulty ignition control circuit inside the engine control module
  • Worn or incorrectly gapped spark plugs preventing proper combustion
  • Moisture or oil contamination in spark plug wells allowing stray current paths
  • Damaged coil wiring or deteriorated coil connectors creating high-resistance connections

How to diagnose B1819

  1. Connect an OBD2 scanner to the vehicle diagnostic port and verify that B1819 is present in the stored codes. Record the freeze frame data associated with the fault — this snapshot reveals engine speed, load percentage, coolant temperature, and vehicle speed at the moment the module detected the problem.
  2. Check for any additional diagnostic trouble codes that may have been set alongside B1819. Related codes often share a common root cause and can guide your inspection toward the most likely failed component. Review manufacturer technical service bulletins for your specific make and model — many B1819 issues have documented factory repairs or software calibrations that address known weaknesses.
  3. Perform a thorough visual inspection of the wiring harness and connectors associated with the rear wiper circuit. Look for damaged insulation, exposed copper strands, corrosion buildup on terminals, and any signs of connector separation or pin damage. Wiggle the harness while observing the connectors to reveal intermittent faults.
  4. Use a digital multimeter to perform continuity testing end-to-end on the wiper rear motor up relay coil circuit. Check each segment of the circuit individually and monitor the reading while gently moving the wiring — fluctuating or open readings indicate a broken wire or poor connection that is not yet completely failed.
  5. Test the relay coil itself for proper resistance using the multimeter and compare the reading to manufacturer specifications. An open coil winding will show infinite resistance and confirms an internally failed relay.
  6. Inspect the spark plugs for wear, carbon fouling, oil contamination, or incorrect electrode gap. Remove each plug and examine the ceramic insulator for cracks that could allow arcing. Check that the gap matches the specification in your service manual.
  7. Clear the code after completing your inspection and repairs, then drive the vehicle through a complete drive cycle that includes the conditions recorded in the freeze frame. If B1819 does not return after this verification drive, the repair is confirmed.

Repair options for B1819

The most cost-effective approach is to address the simplest and most common failures before replacing expensive components. Begin with fuse inspection and connector cleaning, then progress to wiring repair or component replacement as needed.

  • Replace all spark plugs with new units matching the correct heat range and electrode gap: $90–$250
  • Replace a failed ignition coil or coil pack with an OEM-quality replacement: $150–$380
  • Repair damaged coil wiring, replace a faulty connector, or solder broken harness connections: $80–$250

How much does it cost to fix B1819?

The total repair cost depends entirely on which component in the circuit has failed. Based on typical parts and labor rates at independent repair shops in the United States, expect the following scenarios for B1819:

  • Spark plug replacement typically runs $90–$250 including parts and labor
  • Ignition coil or coil pack replacement generally costs $150–$380 depending on the vehicle and part source
  • Wiring harness repair or connector replacement usually falls between $80–$250 depending on labor time and materials

Across all repair scenarios, fixing B1819 most commonly costs between $80 and $380. The key to avoiding unnecessary expense is performing a thorough diagnosis before purchasing parts. Replacing the most expensive component first is almost never the right move — the cheapest fix solves most B1819 faults.

Can you drive with B1819?

Use caution. The underlying fault that sets B1819 can produce engine misfires, and unresolved misfires generate excess heat that damages the catalytic converter over time. If the Check Engine Light is flashing rather than steadily illuminated, do not drive the vehicle — a flashing MIL indicates a active misfire that can quickly destroy emission control hardware. Even with a steady light, schedule diagnosis and repair at the earliest opportunity to prevent secondary damage and unnecessary fuel waste.

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