B1507

What Does Code B1507 Mean?

DTC B1507 signifies a malfunction within the “Flash To Pass” (FTP) switch circuit. This code is typically set by the Body Control Module (BCM), or in some vehicle architectures, an Integrated Power Module (IPM) or Smart Junction Box (SJB), rather than the Engine Control Module (ECM/PCM). The FTP function allows the driver to momentarily activate the vehicle’s high beam headlamps without fully engaging the high beam latching mechanism, usually by pulling the multi-function stalk towards the steering wheel. The BCM continuously monitors the electrical state (voltage, resistance, or current) of the FTP switch input circuit. When the BCM detects a signal from this circuit that falls outside of its predetermined operational parameters – such as a constant open circuit, a continuous short to ground, a continuous short to voltage, or an improbable resistance value – it interprets this as a circuit failure and sets the B1507 code. This indicates that the BCM cannot reliably determine the state of the FTP switch.

Common Symptoms

• Inoperative Flash To Pass Function: The primary and most direct symptom is that the high beams will not momentarily activate when the FTP switch is engaged.
• High Beams Stuck On/Off Momentarily: In rare cases of a short to voltage or ground, the high beams might momentarily activate or fail to turn off as intended, but this is less common with just a circuit failure.
• No Malfunction Indicator Lamp (MIL) Illumination: B-codes (Body codes) typically do not trigger the primary check engine light (MIL) unless mandated by specific vehicle safety regulations or severe integrated system faults. However, a general electrical system warning light or a BCM-specific fault indicator might illuminate on some vehicles.
• Other Related Lighting Issues: Depending on the vehicle’s electrical architecture, a severe fault in the multi-function switch or related wiring could potentially affect other lighting functions or controls integrated into the same stalk, though B1507 specifically points to the FTP circuit.

What Causes the Code B1507?

• Faulty Flash To Pass Switch: The most common cause is an internal electrical or mechanical failure within the multi-function switch itself, preventing proper signal transmission.
• Wiring Harness Issues:
  • Open Circuit: A break or discontinuity in the signal wire between the FTP switch and the BCM.
  • Short Circuit to Ground: The signal wire inadvertently contacting the vehicle’s chassis or another ground source.
  • Short Circuit to Voltage: The signal wire inadvertently contacting a constant power supply wire.
  • Excessive Resistance: Corrosion, chafing, or damaged wire strands causing abnormally high resistance in the circuit.
• Poor Electrical Connections: Corroded, loose, or damaged connector pins at either the multi-function switch or the BCM.
• Faulty Body Control Module (BCM): Although less frequent, an internal failure within the BCM’s input monitoring circuit for the FTP switch can cause this code.

How to Diagnose and Troubleshoot

Diagnosing B1507 requires a systematic approach using a digital multimeter (DMM) and a capable OBD-II scanner:

1. Verify the Complaint: Confirm that the “Flash To Pass” function is indeed inoperative. Engage the switch multiple times to confirm the symptom.
2. Retrieve and Document DTCs: Connect an OBD-II scanner capable of communicating with the BCM. Record all present and pending diagnostic trouble codes. Note if any other B-codes or C-codes (Chassis codes) are present, as they might indicate a related issue.
3. Perform Visual Inspection:
   • Carefully inspect the multi-function switch stalk for any signs of physical damage, looseness, or foreign objects obstructing its movement.
   • Trace the wiring harness from the multi-function switch down the steering column. Look for chafed, cut, pinched, or corroded wires.
   • Inspect the electrical connectors at the multi-function switch and the BCM for bent, corroded, or pushed-out pins, as well as for moisture intrusion.
4. Obtain Wiring Diagrams: Access the vehicle-specific factory wiring diagram for the FTP circuit. This is crucial for identifying the correct power, ground, and signal wires.
5. Test Multi-Function Switch Operation (DMM):
   • Disconnect the electrical connector from the multi-function switch.
   • Using a DMM set to the resistance (Ohms) function, identify the terminals corresponding to the FTP function on the switch itself.
   • With the switch in its normal (released) position, measure resistance. It should typically show an open circuit (OL or very high resistance).
   • Momentarily activate the FTP switch. The DMM should now show a low resistance value (near 0 Ohms) if it’s a simple contact switch, or a specific resistance value if it’s a resistive-ladder type switch. Compare readings to manufacturer specifications. If the switch fails this test, it is faulty.
6. Test Circuit Integrity (DMM):
   • With the multi-function switch connector still disconnected (and the BCM connector potentially disconnected, depending on the test):
   • Continuity Test: Using the DMM set to Ohms, test for continuity between the FTP signal wire terminal at the switch harness connector and its corresponding terminal at the BCM harness connector. Resistance should be very low (typically less than 1 Ohm). High resistance indicates a damaged wire or poor connection.
   • Short to Ground Test: Measure resistance between the FTP signal wire terminal at the harness connector and a known good chassis ground. Resistance should be infinite (OL). Any low resistance indicates a short to ground.
   • Short to Voltage Test: With the ignition ON (and BCM connected, if required by the circuit design), use the DMM set to Volts to check for unintended voltage on the FTP signal wire at the harness connector. There should be no voltage present unless it’s a pull-up circuit from the BCM. Compare to the wiring diagram.
   • Reference Voltage/Ground Check: If the switch circuit utilizes a pull-up voltage or a switched ground, verify the presence of the correct voltage or ground at the appropriate terminal of the multi-function switch harness connector with the ignition ON.
7. Monitor Live Data (if available): If the OBD-II scanner provides live data parameters for the BCM, attempt to monitor the “Flash To Pass Switch Status” or similar input. Observe if the BCM registers the switch activation correctly when engaged. This can help isolate whether the issue is the input signal to the BCM or the BCM’s internal processing.

Recommended Repairs and Solutions

Based on the diagnostic findings, the following repairs are typically recommended:

1. Replace Faulty Multi-Function Switch: If the multi-function switch failed the continuity/resistance test, replace the entire switch assembly. This usually involves removing steering column shrouds and disconnecting electrical connectors. Ensure the replacement part is compatible with the vehicle’s specific options.
2. Repair Wiring Harness: If an open circuit, short to ground, short to voltage, or excessive resistance was identified in the wiring harness, perform the necessary repairs.
   • For opens or shorts, cut out the damaged section of wire and splice in a new section using solder and heat-shrink tubing for a durable, weather-resistant connection.
   • For excessive resistance due to corrosion, clean the affected areas thoroughly or replace the corroded wire/connector pins.
3. Clean or Repair Connectors: If corrosion or poor terminal tension was found at either the switch or BCM connector, use an electrical contact cleaner to remove corrosion and carefully adjust or replace damaged pins. Ensure connectors are fully seated and latched securely.
4. Replace Body Control Module (BCM): Only consider BCM replacement after absolutely ruling out the multi-function switch and all associated wiring and connectors. BCM replacement typically requires advanced diagnostic tools for programming, configuration, and potentially security-related functions, often necessitating dealer-level service.
5. Post-Repair Verification: After completing any repair, clear the DTCs from the BCM using the OBD-II scanner. Re-test the “Flash To Pass” function multiple times to confirm it operates correctly and that the B1507 code does not reappear. If possible, perform a short drive cycle to allow the BCM to re-evaluate the circuit and confirm proper operation.