Introduction:
The diagnostic trouble code (DTC) B1303, "Accessory Delay Relay Coil Circuit Open," indicates a fault within the electrical circuit controlling the accessory delay relay. This relay is crucial for maintaining power to certain vehicle accessories (like the radio, power windows, or interior lights) for a short period after the ignition is turned off, enhancing convenience for the driver and passengers. When this circuit is open, the relay may not function correctly, leading to the accessories shutting off immediately upon turning off the ignition or, conversely, failing to shut off at all, potentially draining the battery. This article will provide a comprehensive overview of the B1303 code, its causes, symptoms, diagnosis, and potential solutions.
| Topic | Description | Potential Impact |
|---|---|---|
| Accessory Delay Relay Function | Controls power to accessories for a short time after ignition is off. Usually powers radio, power windows, interior lights, etc. | Inconvenience, battery drain, malfunctioning accessories. |
| B1303 Code Definition | Indicates an open circuit in the relay coil circuit; ECU detects no current flow to activate the relay. | Relay does not activate or deactivate properly, leading to accessory malfunctions. |
| Common Causes | Faulty relay, wiring issues (broken, corroded, or shorted wires), loose connections, blown fuse, ECU malfunction, poor ground connection. | Intermittent or complete failure of the accessory delay function. |
| Symptoms | Accessories shutting off immediately with ignition, accessories remaining on after ignition is off, battery drain, no accessory function. | Driver inconvenience, potential for battery damage, inability to use accessories. |
| Diagnostic Steps | Visual inspection, fuse check, relay test, voltage/continuity testing of wiring, ECU diagnosis (if all else fails). | Identification of the root cause of the open circuit. |
| Potential Solutions | Relay replacement, wiring repair (splice, replace), connector cleaning/repair, fuse replacement, ECU replacement (rare), ground repair. | Restoration of proper accessory delay function. |
| Tools Needed | Multimeter, wiring diagram, test light, wire stripper/crimper, soldering iron (optional), fuse puller. | Accurate diagnosis and efficient repair. |
| Related Codes | B1300-B1399 (Body Control System Codes), specific codes related to individual accessory circuits. | Can help pinpoint the source of the problem if multiple systems are affected. |
| ECU Involvement | ECU monitors the relay circuit and sets the code when it detects an open. May also provide the ground for the relay coil. | ECU malfunction can sometimes cause the B1303 code, although this is less common. |
| Fuse Location | Varies depending on vehicle make and model; consult the owner's manual or a vehicle-specific wiring diagram. | Protecting other circuits from damage and ensuring proper system operation. |
| Relay Location | Typically located in the fuse box under the hood or inside the cabin; consult the owner's manual or a vehicle-specific repair manual. | Accessibility for testing and replacement. |
Detailed Explanations
Accessory Delay Relay Function:
The accessory delay relay serves as a switch that controls the power supply to various non-essential vehicle accessories after the ignition key is turned off. This allows occupants to continue using features like the radio, power windows, and interior lights for a short period (typically 10-30 minutes) without draining the battery excessively. The relay is triggered by the vehicle's electronic control unit (ECU) or body control module (BCM) when the ignition is turned off.
B1303 Code Definition:
The B1303 diagnostic trouble code signifies that the vehicle's ECU has detected an open circuit within the control circuit of the accessory delay relay. This means the ECU is unable to complete the circuit to activate the relay, preventing it from functioning as intended. The "coil circuit" refers to the winding within the relay that creates an electromagnetic field to close the relay contacts when energized.
Common Causes:
Several factors can contribute to a B1303 code:
- Faulty Relay: The relay itself may be defective, with an open or shorted coil.
- Wiring Issues: Damaged or corroded wiring between the ECU, relay, fuse box, and ground can disrupt the circuit. This includes broken wires, frayed insulation, or loose connections.
- Loose Connections: Poorly connected terminals at the relay, fuse box, or ground points can interrupt the flow of electricity.
- Blown Fuse: A blown fuse in the accessory delay relay circuit will prevent power from reaching the relay coil.
- ECU Malfunction: In rare cases, a malfunctioning ECU can incorrectly detect an open circuit or fail to properly control the relay.
- Poor Ground Connection: The relay coil needs a good ground connection to complete the circuit. A corroded or loose ground can cause an open circuit.
Symptoms:
The symptoms of a B1303 code can vary, but common indicators include:
- Accessories Shutting Off Immediately: The radio, power windows, or interior lights may turn off immediately when the ignition is switched off, without the usual delay.
- Accessories Remaining On: Conversely, the accessories might remain powered on even after the ignition is turned off, potentially draining the battery.
- Battery Drain: Due to the accessories remaining powered on, the vehicle's battery can be drained, especially if the issue is not addressed promptly.
- No Accessory Function: In some cases, the accessories might not function at all, even with the ignition on.
Diagnostic Steps:
Diagnosing a B1303 code requires a systematic approach:
- Visual Inspection: Begin by visually inspecting the wiring, connectors, and relay for any signs of damage, corrosion, or loose connections.
- Fuse Check: Check the fuse associated with the accessory delay relay using a test light or multimeter to ensure it is not blown. Consult the owner's manual for the fuse location.
- Relay Test: Test the relay itself. You can swap it with a known good relay of the same type or use a multimeter to check for continuity across the coil terminals. An open circuit indicates a faulty relay.
- Voltage/Continuity Testing: Use a multimeter to check for voltage and continuity in the wiring between the ECU, relay, fuse box, and ground points. Refer to a vehicle-specific wiring diagram to identify the correct wires and connections. Check for voltage at the relay when the ignition is in the "run" position.
- ECU Diagnosis: If all other components check out, consider the possibility of an ECU malfunction. This is less common but should be investigated if other diagnostic steps fail to identify the problem.
Potential Solutions:
The appropriate solution depends on the root cause of the B1303 code:
- Relay Replacement: If the relay is faulty, replace it with a new one.
- Wiring Repair: Repair any damaged or corroded wiring by splicing in new sections of wire, replacing connectors, or cleaning corroded terminals.
- Connector Cleaning/Repair: Clean corroded connectors with electrical contact cleaner and ensure they are securely connected. Repair or replace damaged connectors.
- Fuse Replacement: Replace a blown fuse with a new one of the correct amperage.
- ECU Replacement (Rare): If the ECU is determined to be the cause, it may need to be replaced and reprogrammed. This is a complex procedure best left to a qualified technician.
- Ground Repair: Clean and tighten any loose or corroded ground connections associated with the accessory delay relay circuit.
Tools Needed:
To effectively diagnose and repair a B1303 code, you will need the following tools:
- Multimeter: For testing voltage, continuity, and resistance.
- Wiring Diagram: To identify the correct wires and connections.
- Test Light: For checking for power and ground.
- Wire Stripper/Crimper: For repairing or replacing wiring.
- Soldering Iron (Optional): For making permanent wire connections.
- Fuse Puller: For removing fuses without damaging them.
Related Codes:
While B1303 specifically relates to the accessory delay relay coil circuit, other related codes within the B1300-B1399 range (Body Control System Codes) or specific codes related to individual accessory circuits might be present. These codes can provide additional clues to the underlying problem. For example, a code related to a specific power window motor or the radio circuit might indicate a more localized wiring issue affecting both the accessory delay relay and the affected accessory.
ECU Involvement:
The ECU plays a crucial role in the accessory delay system. It monitors the state of the ignition switch and, based on this information, activates or deactivates the accessory delay relay. The ECU often provides the ground path for the relay coil. When the ECU detects an open circuit in the relay coil circuit (no current flow), it sets the B1303 code. While ECU malfunction is a less frequent cause, it's important to consider, especially if all other components test correctly.
Fuse Location:
The location of the fuse protecting the accessory delay relay circuit varies depending on the vehicle's make, model, and year. Consult the owner's manual or a vehicle-specific wiring diagram to identify the correct fuse. It is typically located in the fuse box under the hood or inside the cabin.
Relay Location:
Similar to the fuse, the location of the accessory delay relay varies by vehicle. It's typically found in the fuse box, either under the hood or inside the cabin. Refer to the owner's manual or a vehicle-specific repair manual to pinpoint its exact location.
Frequently Asked Questions
What does the B1303 code mean?
It means there's an open circuit in the accessory delay relay coil circuit, preventing the relay from working properly.
What are the common symptoms of a B1303 code?
Accessories may shut off immediately with the ignition, remain on after ignition off, or not function at all.
Can a bad fuse cause a B1303 code?
Yes, a blown fuse in the accessory delay relay circuit can prevent power from reaching the relay coil.
How do I test the accessory delay relay?
You can swap it with a known good relay or use a multimeter to check for continuity across the coil terminals.
Can a faulty ECU cause a B1303 code?
While less common, an ECU malfunction can incorrectly detect an open circuit or fail to control the relay.
Conclusion
The B1303 code indicates a problem in the accessory delay relay coil circuit, leading to inconveniences and potential battery drain. A systematic approach to diagnosis, including visual inspection, fuse and relay testing, and voltage/continuity checks, is crucial for identifying the root cause. Repairing or replacing faulty components, such as the relay, wiring, connectors, or fuses, will typically resolve the issue and restore proper accessory delay function. Always consult a vehicle-specific wiring diagram for accurate information and consider seeking professional assistance if you are not comfortable performing electrical repairs.