B1352

What Does Code B1352 Mean?

DTC B1352 signifies an “Ignition Key-In Circuit Failure.” This code is typically set by the Body Control Module (BCM), Instrument Panel Cluster (IPC), or occasionally the Powertrain Control Module (PCM), indicating an unexpected or illogical signal state from the ignition key-in switch circuit. This switch is located within the ignition lock cylinder housing and is designed to detect the physical presence of a key. When a key is inserted, the switch closes (or opens, depending on design), sending a voltage signal or grounding a circuit to the respective control module. The BCM utilizes this input for various convenience features such as the key-in warning chime, Retained Accessory Power (RAP) functionality, and interaction with the vehicle’s security system. The B1352 code is logged when the module detects a discrepancy, such as a continuous “key-in” signal when no key is physically present, or a continuous “key-out” signal when a key is known to be inserted (e.g., ignition in “OFF” or “ACC” position with door open).

Common Symptoms

• Key-in Warning Chime Malfunction: The chime may sound continuously even after the key is removed, or fail to sound when the key is inserted and a door is open.
• Erratic Retained Accessory Power (RAP): Accessories (e.g., radio, power windows) may not stay on after the ignition is turned off and the door is opened, or they may remain on indefinitely, leading to potential battery drain.
• Security System Irregularities: The vehicle’s alarm or security system may not arm or disarm correctly, or it could trigger false alarms.
• Remote Start Inoperability: If equipped, the remote start feature may be disabled or function inconsistently.
• Battery Drain: If the module falsely detects a key-in state, certain vehicle systems may remain active longer than intended, resulting in a parasitic battery draw.

What Causes the Code B1352?

• Faulty Ignition Key-In Switch: The most prevalent cause, involving mechanical wear, sticking, or internal electrical failure of the switch located within the ignition lock cylinder.
• Wiring Harness Issues:
  • Open Circuit: A break or high resistance in the signal wire connecting the key-in switch to the control module.
  • Short to Ground: The signal wire is inadvertently grounded, causing the control module to perpetually detect a “key-in” state.
  • Short to Voltage: The signal wire is inadvertently exposed to battery voltage or another power source, causing a continuous “key-in” signal.
  • Corrosion: At electrical connectors or within the wiring itself, leading to intermittent or complete signal loss.
• Faulty Control Module: Less common, but an internal fault within the BCM, IPC, or PCM’s input circuit for the key-in signal can generate this code.
• Physical Damage to Ignition Lock Cylinder: Damage that prevents the key-in switch from correctly actuating, even if the switch itself is electrically sound.

How to Diagnose and Troubleshoot

Diagnosis of B1352 requires careful electrical testing and systematic verification:

1. Initial Scan Tool Analysis: Connect an OBD-II scan tool capable of communicating with the BCM, IPC, or relevant module. Confirm B1352 is active or stored. Review live data for “Ignition Key Status,” “Key In Switch State,” or similar parameters. Insert and remove the key multiple times while observing the scan tool data. The parameter should accurately reflect the key’s physical presence. If the scan tool data is inconsistent with the key’s actual position, proceed with circuit testing.
2. Visual Inspection:
   • Inspect the ignition lock cylinder for any physical damage, debris, or binding that could interfere with the key-in switch.
   • Examine the wiring harness leading to the ignition lock cylinder for visible damage, chafing, or corrosion.
3. Obtain Wiring Diagrams: Acquire the vehicle-specific wiring diagram for the ignition key-in switch circuit. This will identify the wire colors, pin locations at connectors, the specific control module involved, and the expected electrical behavior of the switch (e.g., normally open, normally closed, resistance values).
4. Test Key-In Switch (Component Level):
   • Disconnect the battery’s negative terminal for safety.
   • Locate and disconnect the electrical connector at the key-in switch, typically on the backside of the ignition lock cylinder.
   • Using a Digital Multimeter (DMM) set to ohms, test the switch:
     • With the key removed, check for continuity or specific resistance as per the wiring diagram.
     • Insert the key and recheck. The switch should change state (e.g., from open/infinite resistance to closed/near 0 ohms, or vice-versa, or a specific resistance value).
   • If the switch does not change state correctly, it is likely faulty.
5. Test Wiring Harness (Circuit Integrity):
   • With the key-in switch connector and the control module connector disconnected (ensure battery is disconnected), use the DMM for the following:
     • Continuity Test: Check for continuity between the key-in switch connector’s signal wire pin and the corresponding signal input pin at the control module connector. Resistance should be less than 0.5 ohms.
     • Short to Ground Test: Check for continuity between the signal wire at both the switch and module ends and chassis ground. There should be no continuity (OL – Over Limit/Open Line).
     • Short to Voltage Test: Reconnect the battery (temporarily) with the control module still disconnected. Use the DMM set to DC volts to check for any unintended voltage on the signal wire with the key removed and ignition off. Any significant voltage (e.g., near battery voltage) indicates a short to voltage.
   • Inspect all associated inline connectors for corrosion or loose pins.
6. Control Module Input Verification: If the switch and wiring test perfectly, and the scan tool still shows incorrect key status, it may indicate an internal fault within the control module. This is rare for a B1352.

Recommended Repairs and Solutions

The repair strategy for B1352 directly follows the diagnostic findings:

• Replace Ignition Key-In Switch: In the majority of cases, replacing the faulty key-in switch will resolve the issue. Confirm that the replacement switch is the correct part number for the vehicle. Follow manufacturer-specific procedures for removal and installation, ensuring the switch is correctly indexed and secured within the ignition lock cylinder assembly.
• Repair Wiring Harness: If an open circuit, short to ground, short to voltage, or high resistance due to corrosion is identified in the wiring, the affected section of the harness must be repaired. Use appropriate gauge wire, high-quality solder, and heat-shrink tubing for durable, weather-resistant repairs. Clean any corroded electrical connectors with a dedicated electrical contact cleaner and apply dielectric grease to prevent future corrosion.
• Replace Ignition Lock Cylinder Assembly: If the key-in switch is an integral, non-serviceable part of the ignition lock cylinder, or if physical damage to the lock cylinder itself prevents proper switch operation, the entire assembly may need replacement. Be aware that replacing the lock cylinder often necessitates key reprogramming or immobilization system relearning, which typically requires specialized diagnostic equipment or dealer service.
• Replace Control Module: Only as a last resort, after meticulously confirming that the key-in switch and all associated wiring are unequivocally functional and the issue persists. Control module replacement is typically an expensive repair and almost always requires programming, configuration, and potentially security system relearn procedures.
• Post-Repair Verification: After completing the repair, clear all stored DTCs using an OBD-II scanner. Cycle the ignition and insert/remove the key multiple times. Verify that the key-in warning chime, Retained Accessory Power (RAP), and any other affected convenience features now operate correctly. Perform another scan to ensure the B1352 code does not return.