Buick Code P1377 – Ignition Control Module 4X Reference Pulse Incorrect Camshaft Reference Pulse

P1377 Code Description Buick

The Buick diagnostic trouble code P1377 (DTC) indicates a problem with the Ignition Control Module (ICM) not receiving the correct ratio between the camshaft reference pulse and the 4X reference pulse. This issue typically occurs in vehicles equipped with a distributorless ignition system, where the ICM plays a crucial role in controlling ignition timing. The ICM uses inputs from the Camshaft Position Sensor (CMP) and the Crankshaft Position Sensor (CKP) to determine the correct ignition timing for the spark plugs. When the ICM does not receive the proper signal ratio from the camshaft and crankshaft sensors, it can lead to misfires, rough idling, poor acceleration, and potentially engine stalling.

Common Causes of Buick P1377 Code

NOTE: The listed causes may not be a complete list of all potential issues, and there could be other causes.

1. Faulty Camshaft Position Sensor: A defective CMP sensor can send incorrect signals to the ICM, triggering the P1377 code.
2. Faulty Crankshaft Position Sensor: A defective CKP sensor can also disrupt the signal ratio between the camshaft and crankshaft sensors.
3. Wiring Issues: Poor electrical connections, damaged wiring, or corroded connectors can interfere with signal transmission.
4. ICM Failure: The Ignition Control Module itself may be faulty, causing it to misinterpret sensor signals.
5. ECU Malfunction: In rare cases, an issue with the Engine Control Unit (ECU) can also trigger this DTC by sending incorrect commands to the ICM.

Symptoms of Buick P1377 Code

1. Unstable Idle or Hesitation: The engine may run unevenly or struggle to maintain a steady idle speed.
2. Misfires: The vehicle may experience intermittent misfires, resulting in a lack of power and irregular operation.
3. Engine Stalling: The engine may stall unexpectedly, especially at idle or when coming to a stop.
4. Reduced Fuel Efficiency: The vehicle may consume more fuel than usual due to inefficient combustion caused by incorrect ignition timing.

How to Fix Buick P1377 Code

1. Diagnose the Problem: Use a diagnostic scan tool to confirm the P1377 code and perform additional tests to identify the exact cause, such as checking CMP and CKP sensor signals.
2. Replace Faulty Sensors: If the camshaft or crankshaft position sensors are found to be defective, replace them with new OEM-quality parts.
3. Check Wiring and Connectors: Inspect the wiring harness, connectors, and grounds for any signs of damage or corrosion. Repair or replace as necessary.
4. Test the Ignition Control Module: If all sensors and wiring are correct, the ICM may need to be tested or replaced if found faulty.
5. Clear Codes and Perform a Road Test: After completing repairs, clear the DTC and road test the vehicle to ensure the issue has been resolved.