B1364

What Does Code B1364 Mean?

DTC B1364 signifies an “Ignition Start Circuit Open” condition. This code is typically set by the Body Control Module (BCM), or in some vehicle architectures, the Powertrain Control Module (PCM/ECM), when it detects an open circuit in the electrical path responsible for signaling the starter motor to engage. Specifically, the module monitors a dedicated circuit that carries the “start” command originating from the ignition switch (or push-button start system) to the starter relay or solenoid. An “open circuit” means there is a break in the continuity of this electrical path, preventing current flow. This fault directly impacts the vehicle’s starting system, as the module cannot confirm or transmit the request to crank the engine, leading to a no-crank condition.

Common Symptoms

• Vehicle will not crank when the ignition key is turned to the “START” position or the start button is pressed.
• Engine fails to start entirely.
• Starter motor does not engage or make any noise.
• Dashboard warning lights (e.g., battery light, security light) may illuminate in conjunction with the no-start condition.
• Other electrical accessories may function normally, indicating the primary battery and main power distribution are intact.

What Causes the Code B1364?

• Faulty Ignition Switch: Internal mechanical or electrical failure of the ignition switch, specifically in the “START” position contact, preventing the voltage signal from being sent.
• Open or Damaged Wiring: A break, significant corrosion, chafing, or a high-resistance point in the wiring harness connecting the ignition switch to the BCM/PCM, the neutral safety switch/clutch pedal position switch, or the starter relay control circuit.
• Blown Fuse: A fuse that protects the ignition start circuit, the starter relay control circuit, or the power supply to the ignition switch may have failed.
• Faulty Neutral Safety Switch (Automatic Transmissions) or Clutch Pedal Position Switch (Manual Transmissions): An internal open circuit within these switches, or an open in their associated wiring, preventing the start signal from being completed to the BCM/PCM.
• Faulty Starter Relay (Control Side): An open circuit in the coil windings of the starter relay itself, or an issue with the ground or power supply to the relay’s control side.
• Faulty Body Control Module (BCM) or Powertrain Control Module (PCM): Internal module failure where the input for the ignition start signal is not being processed correctly, or the output signal to the starter relay is not being sent. This is less common than external wiring or switch failures.

How to Diagnose and Troubleshoot

Diagnosis of B1364 requires a systematic approach, utilizing a digital multimeter (DMM), wiring diagrams, and potentially an advanced OBD-II scanner with bi-directional control capabilities.

1. Verify Code and Symptoms: Connect an OBD-II scanner to confirm B1364 is present. Clear the code and attempt to replicate the no-start condition. Note any other accompanying DTCs.
2. Check Fuses: Consult the vehicle’s service manual to identify all fuses related to the ignition switch, starter motor, BCM/PCM, and starter relay. Using a DMM, check for continuity across each relevant fuse. A blown fuse will show infinite resistance (OL). Replace any blown fuses with the correct amperage rating.
3. Visual Inspection of Wiring: Thoroughly inspect the wiring harness from the ignition switch, through any safety switches (neutral safety/clutch pedal position), to the BCM/PCM, and finally to the starter relay. Look for signs of physical damage, corrosion, loose connectors, or repairs. Pay close attention to areas where the harness bends, passes through firewalls, or is exposed to heat/vibration.
4. Test Ignition Switch Output:
   • Access the connector for the ignition switch.
   • Refer to the wiring diagram to identify the ignition “START” signal wire.
   • Using a DMM, back-probe this wire with the negative lead connected to a known good ground.
   • Turn the ignition key to the “START” position and observe the voltage reading. You should see battery voltage (approximately 12V). If no voltage is present, the ignition switch is likely faulty, or its input power source is open.
5. Test Safety Switches (Neutral Safety/Clutch Pedal Position):
   • Locate the appropriate safety switch.
   • Using the wiring diagram, identify the input and output wires for the start signal.
   • Test for continuity or voltage drop across the switch while it is in the “start permissive” position (e.g., shifter in Park/Neutral, clutch pedal fully depressed). An open circuit or significant voltage drop indicates a faulty switch or its associated wiring.
6. Test Starter Relay Control Circuit:
   • Locate the starter relay (often in the under-hood fuse box).
   • Identify the control circuit terminals (typically pins 85 and 86 on a Bosch-style relay).
   • With the ignition key in the “START” position, use the DMM to check for the presence of power and ground at these terminals. One side typically receives battery voltage from the BCM/PCM (after processing the ignition start signal), and the other side is connected to ground (either constant or switched by the BCM/PCM). Lack of power or ground indicates an open circuit in the control wiring from the BCM/PCM to the relay, or a BCM/PCM output issue.
7. Continuity Test of Wiring Segments: If a lack of voltage or continuity is identified at an intermediate point, isolate the specific wire segment. Disconnect both ends of the suspect wire and perform a continuity test with the DMM. An “OL” (Open Line) reading confirms an open circuit. Also, check for shorts to ground or power in the circuit.
8. BCM/PCM Input/Output Test: If all external components and wiring test good up to the BCM/PCM, the issue may lie within the control module itself. With wiring diagrams, test the input signal at the BCM/PCM connector from the ignition switch/safety switches. If the input is present but the module is not outputting the control signal to the starter relay, the BCM/PCM may be faulty. This typically requires specialized diagnostic tools for confirmation.

Recommended Repairs and Solutions

Once the root cause of the B1364 code has been precisely identified through diagnosis, the following repairs are typically recommended:

• Replace Blown Fuses: If a blown fuse is found, replace it with a new fuse of the exact specified amperage. Investigate any underlying cause for the fuse blowing, such as a short circuit elsewhere in the system, to prevent recurrence.
• Repair or Replace Damaged Wiring: If an open circuit or high resistance is identified in the wiring harness, perform a professional repair by soldering and heat-shrinking the connection, or replace the entire affected harness section if damage is extensive. Ensure proper routing and protection of new wiring.
• Replace Faulty Ignition Switch: If the ignition switch fails to output voltage in the “START” position, it must be replaced. Ensure the new switch is compatible and, if applicable, correctly coded or programmed to the vehicle’s immobilizer system.
• Replace Faulty Neutral Safety Switch or Clutch Pedal Position Switch: If diagnostic tests confirm an internal open or failure of these safety switches, replacement is necessary. Verify proper adjustment after installation.
• Replace Faulty Starter Relay: If the starter relay’s control circuit receives proper power and ground but the relay does not energize or pass current to the starter solenoid, the relay itself is faulty and should be replaced.
• Replace Body Control Module (BCM) or Powertrain Control Module (PCM): This repair is reserved as a last resort, only after all other potential causes (wiring, switches, fuses, relays) have been exhaustively tested and ruled out. BCM/PCM replacement almost always requires programming, coding, or initialization to the specific vehicle, which typically necessitates factory-level diagnostic equipment and expertise.

Important Mechanic’s Tip: Always disconnect the vehicle’s battery terminals before performing any electrical repairs to prevent accidental shorts or damage to sensitive electronic components. After repairs are completed, clear the DTC B1364 with an OBD-II scanner and perform multiple start cycles to confirm the issue is resolved and the code does not return. Additionally, research any applicable Technical Service Bulletins (TSBs) for the specific vehicle make and model, as manufacturers often identify common failure points for certain codes.