Introduction:
The B1818 trouble code indicates a fault within the rear wiper motor up relay coil circuit. This circuit is crucial for the proper functioning of the rear windshield wiper, ensuring clear visibility during inclement weather. Failure in this circuit can lead to a non-operational rear wiper, posing a safety hazard, especially in conditions with rain, snow, or road spray.
Table: B1818 Wiper Rear Motor Up Relay Coil Circuit Failure - Comprehensive Breakdown
| Aspect | Description | Potential Causes |
|---|---|---|
| Definition | Diagnostic Trouble Code (DTC) indicating a malfunction in the circuit controlling the relay that engages the rear wiper motor in the "up" or "on" position. | Open or shorted wiring in the relay coil circuit; faulty rear wiper motor up relay; corroded or damaged connectors; malfunctioning Powertrain Control Module (PCM) or Body Control Module (BCM); high resistance in the circuit; blown fuse related to the rear wiper system. |
| Symptoms | Rear wiper not functioning; rear wiper stuck in one position; intermittent rear wiper operation; rear wiper operates continuously; Check Engine Light illuminated (though less common, depending on the vehicle); other electrical issues related to the rear of the vehicle. | |
| Relay Function | An electromagnetic switch that controls the power supply to the rear wiper motor when activated. The "up" relay ensures the motor receives power to operate. | Relay failure; corroded relay terminals; shorted or open coil within the relay; incorrect relay type installed; relay improperly seated in the fuse box. |
| Coil Circuit | The winding within the relay that creates an electromagnetic field when energized, pulling the relay contacts together and completing the circuit to the wiper motor. | Open circuit in the coil winding; short circuit in the coil winding; high resistance in the coil winding; damaged insulation on the coil winding; voltage supply issue to the coil. |
| Wiring & Connectors | The wires and connectors that carry the electrical signals to and from the relay and the PCM/BCM. | Damaged or corroded wiring; loose or disconnected connectors; short to ground in the wiring; open circuit in the wiring; water intrusion into connectors; rodent damage to wiring; chafed or broken wires. |
| PCM/BCM Involvement | The computer modules that control various vehicle functions, including the rear wiper system. | Internal failure of the PCM/BCM; software glitch in the PCM/BCM; faulty output driver in the PCM/BCM responsible for controlling the relay; incorrect programming of the PCM/BCM; water damage to the PCM/BCM. |
| Diagnostic Procedure | Visual inspection; multimeter testing; scan tool diagnosis; relay testing; wiring diagram analysis. | Checking fuses; inspecting wiring and connectors for damage; testing the relay for proper operation; checking voltage and ground at the relay coil; using a scan tool to read DTCs and monitor data; performing a continuity test on the wiring; checking the PCM/BCM for proper operation. |
| Repair Strategies | Replacing faulty relay; repairing or replacing damaged wiring; cleaning or replacing corroded connectors; replacing the PCM/BCM (in rare cases); reprogramming the PCM/BCM; cleaning and drying water-damaged components. | |
| Tools Required | Multimeter; scan tool; wiring diagram; relay tester; wire stripper/crimper; soldering iron; electrical tape; dielectric grease; socket set; wrench set. | |
| Safety Precautions | Disconnect the battery before working on electrical components; use caution when working with electrical circuits; wear appropriate safety gear (e.g., gloves, eye protection); consult a repair manual or qualified technician if unsure about any procedure. | |
| Related DTCs | Other DTCs related to the rear wiper system or electrical faults in the vehicle. | B1819 (Wiper Rear Motor Down Relay Coil Circuit Failure); B1820 (Wiper Rear Motor Malfunction); circuit low or high voltage codes; general electrical system codes. |
| Common Misdiagnoses | Assuming the wiper motor is faulty without testing the relay and wiring; overlooking corroded connectors; failing to properly test the relay coil circuit; neglecting to check for blown fuses. | |
| Component Location | Location of the rear wiper motor up relay, wiring, and connectors varies depending on the vehicle make and model. Consult a repair manual or wiring diagram. | Typically found in the fuse box (under the hood or in the passenger compartment); wiring runs along the vehicle's chassis to the rear wiper motor; connectors are often located near the relay, the wiper motor, and the PCM/BCM. |
| Voltage Requirements | The voltage required to activate the relay coil and power the rear wiper motor varies depending on the vehicle. Consult a repair manual or wiring diagram. | Typically 12 volts DC for the relay coil and the wiper motor; voltage drop can indicate a wiring problem; insufficient voltage can prevent the relay from activating. |
| Resistance Values | Expected resistance values for the relay coil and the wiring can vary depending on the vehicle. Consult a repair manual or wiring diagram. | High resistance in the wiring can indicate corrosion or a loose connection; an open circuit will have infinite resistance; a short circuit will have very low resistance. |
Detailed Explanations:
Definition: The B1818 code pinpoints a specific electrical issue: a malfunction in the circuit that controls the relay responsible for powering the rear wiper motor. This relay acts as a switch, and the B1818 code indicates a problem with the relay's control circuit, not necessarily the wiper motor itself.
Symptoms: The most obvious symptom is a non-functional rear wiper. However, other symptoms can include the wiper being stuck in a particular position, intermittent operation (working sometimes, not others), or continuous operation even when the switch is off. A Check Engine Light might illuminate, though this is less common with rear wiper issues.
Relay Function: A relay is an electrically operated switch. In this case, the rear wiper motor up relay uses a small electrical current to control a larger current that powers the wiper motor. When the relay is activated, it allows power to flow to the wiper motor, causing it to operate.
Coil Circuit: The relay coil is a winding of wire inside the relay. When voltage is applied to the coil, it creates a magnetic field. This magnetic field pulls a set of contacts together, completing the circuit and allowing power to flow to the rear wiper motor. The B1818 code specifically refers to a problem within this coil circuit.
Wiring & Connectors: The wiring and connectors are the pathways for electrical signals. They connect the relay to the power source, the control module (PCM/BCM), and the wiper motor. Damage, corrosion, or loose connections in these components can disrupt the electrical flow and trigger the B1818 code.
PCM/BCM Involvement: The Powertrain Control Module (PCM) or Body Control Module (BCM) is the "brain" that controls many of the vehicle's functions, including the rear wiper system. The PCM/BCM sends a signal to the relay, telling it when to activate the rear wiper. A fault within the PCM/BCM itself, or its programming, can prevent it from properly controlling the relay.
Diagnostic Procedure: Diagnosing a B1818 code involves a systematic approach. Start with a visual inspection of the wiring and connectors. Use a multimeter to check for voltage, ground, and continuity in the relay coil circuit. A scan tool can be used to read DTCs and monitor data. Finally, test the relay itself to ensure it's functioning correctly.
Repair Strategies: The repair strategy depends on the cause of the problem. If the relay is faulty, it should be replaced. Damaged wiring or corroded connectors should be repaired or replaced. In rare cases, a faulty PCM/BCM may need to be replaced or reprogrammed.
Tools Required: A multimeter is essential for testing electrical circuits. A scan tool is helpful for reading DTCs and monitoring data. Other tools include a wiring diagram, relay tester, wire stripper/crimper, soldering iron, electrical tape, dielectric grease, socket set, and wrench set.
Safety Precautions: Always disconnect the battery before working on electrical components to prevent accidental shocks or damage to the vehicle's electrical system. Wear appropriate safety gear, such as gloves and eye protection. If you are unsure about any procedure, consult a repair manual or a qualified technician.
Related DTCs: Other DTCs that may be related to the B1818 code include B1819 (Wiper Rear Motor Down Relay Coil Circuit Failure), B1820 (Wiper Rear Motor Malfunction), and other codes related to electrical circuits, low voltage, or high voltage.
Common Misdiagnoses: A common mistake is to assume the wiper motor is faulty without thoroughly testing the relay and wiring. Also, overlooking corroded connectors or failing to properly test the relay coil circuit can lead to misdiagnosis. It's crucial to follow a systematic diagnostic procedure.
Component Location: The location of the rear wiper motor up relay, wiring, and connectors varies depending on the vehicle make and model. Consult a repair manual or wiring diagram for specific information. Relay locations are usually in fuse boxes inside the cabin or under the hood.
Voltage Requirements: Typically, the relay coil and the rear wiper motor operate on 12 volts DC. A significant voltage drop in the circuit can indicate a wiring problem or a faulty component. Always consult the vehicle's wiring diagram for specific voltage requirements.
Resistance Values: The expected resistance values for the relay coil and the wiring can vary. Consult a repair manual or wiring diagram for specific information. High resistance can indicate corrosion or a loose connection, while an open circuit will have infinite resistance.
Frequently Asked Questions:
-
What does the B1818 code mean? It indicates a problem in the circuit controlling the rear wiper motor up relay.
-
Will my car fail inspection with this code? It depends on your local regulations, but a non-functioning rear wiper could cause a failure.
-
Can I fix this myself? If you have electrical troubleshooting skills and the necessary tools, you may be able to fix it. Otherwise, seek professional help.
-
How much will it cost to fix? The cost depends on the cause of the problem and the labor rate of the repair shop.
-
Is it safe to drive with this code? It's generally safe, but a non-functioning rear wiper can reduce visibility in bad weather.
-
Where is the rear wiper relay located? This varies by vehicle, check your owner's manual or a repair database for your vehicle's specific location.
-
What is a relay coil? It's the winding inside the relay that creates a magnetic field to activate the switch.
Conclusion:
The B1818 code signifies a problem in the rear wiper motor up relay coil circuit, typically leading to a non-operational rear wiper. A systematic diagnostic approach, including checking the relay, wiring, and PCM/BCM, is crucial for accurate diagnosis and effective repair. Addressing this issue promptly ensures safe driving conditions and proper functionality of the rear wiper system.