B1475

What Does Code B1475 Mean?

DTC B1475 signifies an “Accessory Delay Relay Contact Short To Battery.” This diagnostic trouble code is typically registered by the Body Control Module (BCM), General Electronic Module (GEM), or a similar integrated control unit responsible for vehicle body electronics. The accessory delay relay, often part of the Retained Accessory Power (RAP) system, is designed to supply power to certain convenience accessories (e.g., power windows, radio, sunroof, 12V power outlets) for a brief period after the ignition is turned off, usually until a door is opened or a specified time elapses. Code B1475 indicates that the control module has detected a continuous battery voltage (B+) on the output circuit of this relay’s power contacts, even when the relay coil is de-energized and the accessory power should be off. This implies an unintended and uncontrolled energization of the accessory circuit, either due to the relay’s contacts being physically stuck closed or a direct short to a constant battery voltage source within the wiring downstream of the relay.

Common Symptoms

• Accessories Remain Powered: Components like the radio, power windows, sunroof, or 12V power outlets remain active even after the ignition is switched off and all doors are closed.
• Parasitic Battery Drain: An ongoing, unintended current draw from the battery can occur, leading to a discharged battery, especially after the vehicle has been parked for an extended period.
• Non-Operational Accessories: In some cases, while the code indicates a short to battery, the sustained voltage might disrupt the proper control logic, leading to intermittent or complete non-operation of the associated accessories.
• Relay Clicking: While less common for a “stuck closed” condition, an intermittently failing relay might cause audible clicking even when the ignition is off.

What Causes the Code B1475?

• Faulty Accessory Delay Relay: The most prevalent cause is an internal mechanical failure of the relay itself, where the power contacts become fused or welded in the closed (energized) position, regardless of the control coil’s state.
• Wiring Harness Short to Battery: A common issue is physical damage to the wiring harness on the output side of the accessory delay relay, causing the conductor to short circuit directly to a constant 12-volt battery supply wire or a component that is always hot. This could be due to chafing, corrosion, or impact damage.
• Internal Fault within the Control Module (BCM/GEM): Less frequently, the control module’s internal circuitry responsible for monitoring the relay’s output or controlling its coil may malfunction, erroneously reporting a short to battery or continuously energizing the relay coil.
• Damaged Fuse Box or Junction Block: If the accessory delay relay is integrated into a larger fuse box or junction block, an internal fault or short within this assembly could lead to the B1475 code.

How to Diagnose and Troubleshoot

1. Preliminary Visual Inspection: Begin by performing a thorough visual inspection of the accessory delay relay and its associated wiring. Look for signs of chafing, burnt insulation, corrosion, or loose connections, particularly where the wiring passes through the firewall or near sharp metal edges. Inspect the relay itself for any external damage or signs of overheating.

2. Retrieve Freeze Frame Data: Connect an OBD-II scan tool and retrieve any stored freeze frame data along with the B1475 code. This data provides valuable information about vehicle operating conditions (e.g., ignition status, battery voltage) at the moment the fault was detected, which can aid in pinpointing the fault.

3. Accessory Delay Relay Testing:

• Locate the Relay: Consult the vehicle’s service manual or fuse box diagram to accurately identify the accessory delay relay.
• Wiggle Test: With the ignition off, gently wiggle the relay in its socket. Observe if any accessories (radio, windows) momentarily activate or deactivate, which could indicate a loose connection or an intermittently faulty relay.
• Bench Test (if removable):

1. Remove the relay from its socket.
2. Using a Digital Multimeter (DMM) set to resistance (Ohms) mode, measure the resistance across the relay’s power contacts (typically pins 30 and 87). With the relay de-energized, there should be infinite resistance (open circuit). If continuity is detected (low resistance), the relay contacts are stuck closed, indicating a faulty relay.
3. Apply 12V to the relay’s control coil terminals (typically pins 85 and 86) using fused jumper wires. The relay should produce an audible “click,” and continuity should now be present between pins 30 and 87. If it fails to click, or if continuity isn’t established, the relay is faulty.

4. Circuit Voltage and Continuity Checks at Relay Socket:

• Voltage Measurement: With the accessory delay relay removed and the ignition off, use a DMM to measure voltage at the relay socket terminals. Identify the terminal that supplies constant battery voltage (pin 30). This should show approximately 12V. Critically, measure the voltage at the accessory circuit output terminal (pin 87). With the ignition off and the control module commanding the relay off, this terminal should read 0V. If 12V is present here, it confirms a short to battery either in the downstream wiring or indicates the relay’s contacts are internally stuck closed.
• Continuity Check for Short to Power: Disconnect the vehicle’s battery. With the accessory delay relay removed, use the DMM in continuity or resistance mode. Test for continuity between the accessory circuit output terminal (pin 87 socket) and other known constant B+ circuits within the fuse box or wiring harness. Any continuity indicates a short.

5. Parasitic Draw Test (if applicable): If battery drain is a symptom, perform a parasitic draw test. Connect an ammeter in series with the negative battery terminal. With all vehicle systems off and doors closed, allow the control modules to “sleep” (typically 15-30 minutes). Observe the current draw. Systematically remove fuses related to the accessory delay relay and its controlled components to identify if the current draw significantly decreases. This can help isolate the specific circuit causing the draw.

Recommended Repairs and Solutions

1. Replace the Accessory Delay Relay: If diagnostic procedures confirm that the relay’s contacts are fused or stuck closed, replacing the relay is the most direct and common solution. Ensure the replacement relay matches the OEM specifications for voltage, amperage, and pin configuration. Using a quality, OEM-equivalent relay is recommended to ensure reliability and proper function.

2. Repair or Replace Damaged Wiring: If the diagnostic process identifies a short to battery within the wiring harness leading from the accessory delay relay to the affected accessories, the damaged section of the wiring must be repaired. Carefully trace the harness to locate the exact point of damage. Repair the wiring using professional automotive repair techniques, such as soldering and heat-shrinking, rather than crimp connectors, for robust and lasting electrical connections. If the damage is extensive, consider replacing the entire segment of the affected harness.

3. Replace the Body Control Module (BCM/GEM): Replacement of the BCM or similar control module should only be considered after all other possibilities, including the relay and wiring, have been thoroughly ruled out. This is a significantly more complex and costly repair, often requiring specialized programming or synchronization with the vehicle’s other control modules. Always consult the factory service manual for specific BCM diagnostic and replacement procedures.

4. Inspect and Replace Fuse Box/Junction Block: If the accessory delay relay is an integral, non-serviceable component of a fuse box or junction block, or if internal damage to the block itself is causing the short, the entire fuse box or junction block may require replacement. This often involves careful transfer of wiring and potentially module programming.

Mechanic’s Tips: Always begin diagnostics with the simplest and most probable causes. A faulty relay is significantly more common than a control module failure or extensive wiring damage. When testing relays, apply voltage and ground to the coil terminals briefly to prevent overheating the coil, especially during repeated testing. For parasitic draw diagnostics, ensure all control modules have entered their low-power “sleep” mode before taking final current measurements, as this can take up to 30 minutes in some vehicles. Detailed documentation of all diagnostic steps and measurements is crucial for effective troubleshooting and future reference.