Timing Reference High Resolution Signal B Too Few Pulses
The P0377 code indicates that the Powertrain Control Module (PCM) has detected an insufficient number of pulses from the high-resolution timing reference signal B. This signal is typically generated by the crankshaft position sensor or camshaft position sensor and is critical for engine timing and fuel injection synchronization. A low pulse count can cause misfires, rough running, and starting difficulties.
1. Most Common Causes
- Faulty crankshaft position sensor
- Damaged or loose wiring/connectors to the sensor
- Intermittent sensor signal due to metal debris on sensor tip
- Failed PCM (rare)
2. Symptoms You Will Notice
- Engine misfire or rough idle
- Hard starting or no start condition
- Check Engine Light illuminated
- Reduced engine power or stalling
3. Step-by-Step Diagnosis
Step 1: Scan for additional codes and record freeze frame data.
Step 2: Visually inspect the crankshaft position sensor wiring and connector for damage, corrosion, or looseness.
Step 3: Test the sensor's resistance and AC voltage output while cranking the engine using a multimeter.
Step 4: Check the sensor's air gap and clean any metal debris from the sensor tip.
Step 5: If sensor and wiring are okay, test the PCM's ability to read the signal (may require oscilloscope).
4. Frequently Asked Questions
Is it safe to drive with this code?▼
No, it is not safe. The vehicle may stall or fail to start, leading to a potential accident or being stranded.
How much does it cost to fix?▼
Typically $50-$150 for a new crankshaft position sensor plus labor, but costs can vary depending on vehicle make and model.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.