Introduction
The B1817 diagnostic trouble code (DTC) indicates a fault within the rear wiper motor down relay coil circuit. Specifically, it signifies a short to ground, meaning an unintended electrical path is allowing current to flow directly to ground, bypassing the normal circuit components. This can prevent the rear wiper from functioning correctly and potentially damage related electrical components. Addressing this issue promptly is crucial to restore proper rear wiper operation and prevent further damage.
Table: B1817 Wiper Rear Motor Down Relay Coil Circuit Short to Ground
| Topic | Description | Potential Causes |
|---|---|---|
| Definition of B1817 | DTC indicating a short to ground in the rear wiper motor down relay coil circuit. The down relay controls the power supply to the wiper motor when it's moving the wiper to its park position. | Wiring harness damage, shorted relay coil, faulty ground connection, damaged rear wiper motor (internally shorted). |
| Symptoms | Non-functioning rear wiper, rear wiper stuck in a position other than the park position, blown fuse (related to the rear wiper circuit), intermittent wiper operation, rear wiper operates continuously. | Damaged wiring, shorted components, system overload. |
| Affected Components | Rear wiper motor, rear wiper motor down relay, wiring harness connecting these components, body control module (BCM) or other control module overseeing rear wiper function, fuses related to the rear wiper circuit, grounding points. | Corrosion, physical damage, electrical overload. |
| Possible Causes | Short to Ground: Damaged wiring insulation allowing direct contact with the vehicle chassis, corroded or damaged connector pins creating a short, internal short within the rear wiper motor down relay coil, internal short within the rear wiper motor itself. Faulty Relay: Malfunctioning relay coil causing a short. | Physical damage to wiring, corrosion in connectors, component failure due to age or stress, improper installation of aftermarket components. |
| Diagnostic Procedures | Visual inspection of wiring and connectors, multimeter testing for continuity to ground, relay testing (resistance and operation), circuit testing with a wiring diagram, scan tool diagnostics for related codes and data streams. | Inadequate tools, lack of diagnostic knowledge, misinterpretation of diagnostic data. |
| Troubleshooting Steps | Locate the rear wiper motor down relay (refer to vehicle-specific wiring diagrams). Visually inspect the relay and surrounding wiring for damage. Test the relay coil for continuity to ground. Check the wiring harness for shorts to ground using a multimeter. Isolate the shorted component by disconnecting components one at a time. | Incorrect wiring diagrams, misidentification of components, overlooking intermittent faults. |
| Common Ground Locations | Grounding points are usually located on the vehicle chassis, often near the rear of the vehicle, under the dashboard, or in the engine compartment. Look for clusters of wires attached to the body with a bolt or screw. | Corrosion at ground points, loose ground connections. |
| Tools Required | Multimeter, wiring diagrams, automotive test light, wire strippers, crimpers, terminal removal tools, scan tool (optional). | Using incorrect tools, lack of familiarity with tools. |
| Repair Procedures | Repair or replace damaged wiring, replace faulty relay, replace faulty rear wiper motor, clean and secure ground connections, reprogram control modules (if necessary). | Improper wiring repairs, using incorrect replacement parts. |
| Related DTCs | Other rear wiper-related DTCs, DTCs related to body control module (BCM) or other control modules involved in rear wiper operation. These could include open circuits or other relay faults. | Misinterpreting related codes, ignoring other underlying issues. |
| Safety Precautions | Disconnect the negative battery terminal before working on electrical components. Use caution when working with electrical wiring. Refer to vehicle-specific repair manuals for proper procedures. | Failure to disconnect battery, working on live circuits. |
| Importance of Wiring Diagrams | Wiring diagrams are essential for identifying the correct wires and components involved in the rear wiper circuit. They show the electrical connections between the various components and the location of ground points. | Using incorrect or outdated wiring diagrams. |
| Relay Function | A relay is an electrically operated switch. In this case, the down relay controls the power supply to the rear wiper motor when the motor needs to move the wiper blade to the park position. The B1817 code indicates a short in the coil of this relay, not necessarily the switching contacts. | Understanding relay operation is crucial for diagnosis. |
| Testing Relay Coil | To test the relay coil, use a multimeter to measure the resistance between the coil terminals (typically pins 85 and 86). A short to ground will show very low resistance (close to 0 ohms) between one of the coil terminals and the relay case (which is connected to ground). A healthy coil will have a resistance value specified in the relay's datasheet. | Misinterpreting resistance readings, testing the wrong pins. |
| Impact of a Short | A short to ground in the relay coil circuit can cause the relay to remain energized constantly, potentially burning out the relay coil or causing other electrical damage. It can also prevent the rear wiper from parking correctly or from operating at all. | Ignoring the short, leading to further damage. |
| Locating the Short | Locating the exact point of the short to ground can be challenging. Carefully inspect the wiring harness for any signs of damage, such as chafing, cuts, or corrosion. Pay particular attention to areas where the harness passes through the vehicle body or near sharp edges. Use a wiring diagram to trace the circuit and identify potential areas of concern. A short finder tool can also be helpful in locating the short. | Using improper techniques, damaging the wiring further. |
| Importance of Connector Inspection | Connectors are often a source of electrical problems. Inspect the connectors for corrosion, bent pins, or loose connections. Clean any corroded connectors with electrical contact cleaner. Ensure that the connectors are properly seated and locked in place. | Overlooking connector issues, causing intermittent problems. |
| Using a Scan Tool | While a scan tool might not directly pinpoint the location of the short to ground, it can provide valuable information about the rear wiper system. It can show the status of the rear wiper switch, the position of the rear wiper motor, and any other related DTCs. This information can help narrow down the possible causes of the problem. | Relying solely on the scan tool, ignoring basic troubleshooting steps. |
Detailed Explanations
Definition of B1817: This code specifically points to a short circuit where the wire carrying power to the rear wiper motor's "down" relay coil is directly connected to the vehicle's ground. This creates an unintended pathway for electricity. The "down" relay is responsible for ensuring the wiper returns to its parked position.
Symptoms: The most obvious symptom is a non-functioning rear wiper. Other symptoms include the wiper being stuck in an unusual position, a blown fuse related to the rear wiper circuit (due to the excessive current draw of the short), intermittent wiper operation, or the wiper running constantly.
Affected Components: The key components involved are the rear wiper motor itself, the rear wiper motor down relay, the wiring harness connecting these components, the BCM (or equivalent control module), fuses, and the ground points.
Possible Causes: The most likely cause is damaged wiring insulation, allowing the wire to contact the vehicle's metal chassis. This could be due to chafing, cuts, or corrosion. Other causes include a shorted relay coil or an internal short within the rear wiper motor.
Diagnostic Procedures: A systematic approach is crucial. Start with a visual inspection of the wiring and connectors. Use a multimeter to check for continuity to ground on the relay coil circuit. Test the relay itself to ensure it's functioning correctly. Refer to wiring diagrams to understand the circuit layout and identify potential problem areas. A scan tool can help read related codes and data.
Troubleshooting Steps: Locate the rear wiper motor down relay (refer to the wiring diagram). Inspect the relay and wiring for damage. Test the relay coil for continuity to ground. Check the wiring harness for shorts to ground using a multimeter. Disconnect components one at a time to isolate the shorted component.
Common Ground Locations: Grounding points are typically located on the vehicle chassis, often near the rear of the vehicle, under the dashboard, or in the engine compartment. Look for clusters of wires attached to the body with a bolt or screw.
Tools Required: A multimeter is essential for electrical testing. Wiring diagrams are crucial for understanding the circuit. An automotive test light can help check for power and ground. Wire strippers, crimpers, and terminal removal tools are needed for wiring repairs. A scan tool (optional) can provide additional diagnostic information.
Repair Procedures: Repair or replace damaged wiring. Replace the faulty relay or rear wiper motor if necessary. Clean and secure ground connections. Reprogram control modules if required (this is less common but possible).
Related DTCs: Be aware of other rear wiper-related DTCs, as well as codes related to the BCM or other control modules involved in rear wiper operation.
Safety Precautions: Always disconnect the negative battery terminal before working on electrical components to prevent accidental shocks or damage. Use caution when working with electrical wiring and refer to vehicle-specific repair manuals for proper procedures.
Importance of Wiring Diagrams: Wiring diagrams are indispensable for identifying the correct wires and components involved in the rear wiper circuit. They illustrate the electrical connections between components and the location of ground points.
Relay Function: The rear wiper down relay is an electrically operated switch. The relay coil, when energized, closes the switch, allowing power to flow to the wiper motor and move it to the park position. The B1817 code specifically indicates a fault within the relay coil circuit, not necessarily the switching contacts themselves.
Testing Relay Coil: Use a multimeter to measure the resistance between the coil terminals (typically pins 85 and 86). A short to ground will show very low resistance (close to 0 ohms) between one of the coil terminals and the relay case (which is connected to ground). A healthy coil will have a specific resistance value (consult the relay's datasheet).
Impact of a Short: A short to ground in the relay coil circuit can cause the relay to remain energized constantly. This can burn out the relay coil or cause other electrical damage. It can also prevent the rear wiper from parking correctly or operating at all.
Locating the Short: Locating the exact point of the short to ground can be difficult. Carefully inspect the wiring harness for any signs of damage, such as chafing, cuts, or corrosion. Pay particular attention to areas where the harness passes through the vehicle body or near sharp edges. Use a wiring diagram to trace the circuit.
Importance of Connector Inspection: Connectors are often a source of electrical problems. Inspect them for corrosion, bent pins, or loose connections. Clean corroded connectors with electrical contact cleaner and ensure they are properly seated and locked.
Using a Scan Tool: While not a direct short-finder, a scan tool can provide valuable information about the rear wiper system's status, the position of the rear wiper motor, and any related DTCs. This information can help narrow down the possible causes.
Frequently Asked Questions
What does the B1817 code mean? The B1817 code means there's a short to ground in the rear wiper motor down relay coil circuit, indicating an unintended electrical path.
What are the common symptoms of a B1817 code? Common symptoms include a non-functioning rear wiper, the wiper being stuck, a blown fuse, or intermittent operation.
What tools do I need to diagnose a B1817 code? You'll need a multimeter, wiring diagrams, an automotive test light, and potentially a scan tool.
How do I test the rear wiper motor down relay? Use a multimeter to measure the resistance between the relay coil terminals and check for continuity to ground. A short to ground will show very low resistance.
Where are the common ground locations on a vehicle? Grounding points are typically located on the chassis, often near the rear, under the dashboard, or in the engine compartment.
Conclusion
The B1817 DTC indicates a serious electrical fault that needs prompt attention. By systematically diagnosing the circuit, inspecting wiring, and testing components, you can identify and repair the short to ground, restoring proper rear wiper function.