B1552

What Does Code B1552 Mean?

DTC B1552 indicates an Open Circuit condition detected within the decklid (trunk lid) release control circuit. This code is typically set by the Body Control Module (BCM), General Module (GM), or a similar integrated body electronics module responsible for monitoring and controlling convenience features such as the power decklid release. The BCM monitors the electrical continuity and current flow through the circuit connected to the decklid release actuator/solenoid. When the BCM attempts to activate the decklid release, it expects to detect a specific range of resistance and current draw. If the module senses an abnormally high resistance or an infinite resistance (an open circuit), meaning the electrical path is interrupted, it will register B1552. This signifies that the command from the BCM to unlock the decklid is not reaching the actuator due to a break in the wiring, a faulty actuator winding, or a poor connection, preventing the physical release mechanism from operating.

Common Symptoms

• Inoperative Decklid Release: The primary symptom is the complete failure of the decklid to open when commanded via the remote key fob, interior cabin switch, or sometimes the exterior key cylinder if electrically integrated.
• No Actuator Sound: There will be no audible click or mechanical engagement sound from the decklid latch mechanism when the release is attempted.
• Warning Light/Message: Depending on the vehicle manufacturer and model, a “Check Trunk Release System” or similar warning message may appear on the instrument cluster or driver information display.
• Intermittent Operation: In cases where the open circuit is due to a partially frayed or chafed wire, the decklid release may work intermittently before failing completely.

What Causes the Code B1552?

• Damaged Wiring Harness: The most prevalent cause, often found in the wiring harness segment that flexes repeatedly as the decklid opens and closes, typically located near the hinges. Wires can become frayed, chafed, or completely severed over time.
• Faulty Decklid Release Actuator/Solenoid: An internal open circuit within the coil winding of the electrical actuator or a broken internal connection within the actuator assembly itself.
• Corrosion or Poor Electrical Connection: Oxidation, dirt, or loose terminals at the electrical connectors for the decklid actuator, the body control module, or intervening inline connectors can create an open circuit.
• Blown Fuse: While an “open circuit” specifically points to a break in continuity rather than a short, a blown fuse supplying power to the circuit would effectively create an open circuit from the perspective of the actuator, preventing power flow.
• Faulty Decklid Release Switch: Less common as a direct cause of “circuit open” for the actuator, but an internal open in the switch itself could prevent the command signal from reaching the BCM or the actuator, depending on the circuit design.
• Faulty Body Control Module (BCM): Rare, but an internal failure within the BCM’s driver circuit for the decklid release, such as a burnt-out transistor or relay, could mimic an open circuit condition on the output side.

How to Diagnose and Troubleshoot

A systematic diagnostic approach is critical for B1552. Always begin with safety precautions, such as disconnecting the vehicle’s battery when performing electrical tests that require component disconnection, if specified by the manufacturer.

1. Visual Inspection:
   • Begin by meticulously inspecting the entire wiring harness that travels from the vehicle body into the decklid. Pay particular attention to areas of high stress and flexing, such as the hinge points, for signs of chafing, cuts, pinching, or corrosion.
   • Examine the electrical connector at the decklid latch/actuator. Look for bent or pushed-out pins, corrosion on the terminals, or a loose connection.
   • Trace the wiring as much as possible to identify any external damage along its path to the BCM or fuse panel.
2. OBD-II Scan Tool Analysis:
   • Connect an advanced diagnostic scanner capable of communicating with the Body Control Module (BCM) or relevant body electronics module.
   • Retrieve all stored and pending Diagnostic Trouble Codes (DTCs) from all applicable modules. Other related codes could provide additional context.
   • Access the BCM’s live data stream. Look for PIDs related to the decklid release switch status (to confirm input to the BCM) and the commanded status of the decklid release actuator.
   • If supported, utilize the bi-directional control function of the scan tool to command the decklid release actuator directly. Listen for the actuator and observe if the circuit status changes on the scan tool.
3. Digital Multimeter (DMM) Testing:
   • Continuity Test (Wiring): Disconnect the electrical connector at the decklid release actuator. Using a DMM set to ohms (Ω) or continuity mode, measure the resistance between the power/signal wire terminal at the actuator’s harness side connector and its corresponding terminal at the BCM connector (if accessible). An “OL” (Open Loop) or extremely high resistance indicates an open circuit in the wiring. Perform the same test for the ground wire.
   • Voltage Drop Test: With the ignition key in the “ON” position and the circuit activated (e.g., holding the decklid release button), carefully backprobe the power supply wire at the actuator’s harness connector. Verify battery voltage (approximately 12V). If no voltage is present, trace the power supply circuit back to its fuse and the BCM. Perform a similar check for the ground circuit integrity using a voltage drop test from the actuator ground to a known good chassis ground while the circuit is activated (expected voltage drop < 0.2V).
   • Actuator Resistance Test: Disconnect the decklid release actuator. Using the DMM set to ohms (Ω), measure the resistance across the actuator’s two electrical terminals. Compare this reading to manufacturer specifications (typically a low resistance value, e.g., 2-20 ohms). An “OL” (Open Loop) indicates an internal open circuit within the actuator, confirming it is faulty.
   • BCM Output Test: If the wiring and actuator test good, carefully backprobe the BCM’s output pin for the decklid release actuator. While commanding the release with a scan tool or the interior switch, observe if the BCM outputs the expected voltage. If the BCM outputs voltage, but it’s not present at the actuator, the fault lies definitively within the wiring harness between the BCM and the actuator.

Recommended Repairs and Solutions

Once the diagnostic process has pinpointed the exact cause of the open circuit, the following repairs are typically performed:

1. Repair or Replace Damaged Wiring: This is the most common repair. If damaged sections of wire are identified, carefully splice in new sections of wire of the correct gauge. Use high-quality solder connections and heat-shrink tubing to ensure robust, weather-resistant, and flexible repairs. Avoid simple crimp connectors in high-flex areas. If the damage is extensive or involves multiple wires, consider replacing the entire harness segment.
2. Replace Decklid Release Actuator: If the actuator itself tests as an open circuit (OL resistance), it must be replaced. Ensure the new actuator is securely mounted, and its electrical connector is clean and properly latched to prevent future issues.
3. Clean and Secure Electrical Connections: If corrosion or loose pins were found at any connectors (actuator, BCM, inline connectors), clean the terminals thoroughly using specialized electrical contact cleaner and a small brush. Apply dielectric grease to the cleaned terminals to prevent future corrosion and ensure a solid electrical connection, then re-seat the connector firmly.
4. Replace Blown Fuse: If a blown fuse was identified as the root cause, replace it with a new fuse of the exact specified amperage. It’s crucial to understand why the fuse blew, as an underlying short circuit could lead to immediate re-blowing of the new fuse, although B1552 typically indicates an open.
5. Body Control Module (BCM) Replacement: This should only be considered after all other components (wiring, actuator, fuses, switches) have been thoroughly tested and confirmed to be in good working order. BCM replacement often requires specialized programming or configuration using a factory-level scan tool to ensure proper vehicle function and integration.