Timing Reference High Resolution Signal B Intermittent/Erratic Pulses
The P0378 code indicates that the Powertrain Control Module (PCM) has detected intermittent or erratic 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 used for precise engine timing and fuel injection control. Erratic pulses can cause misfires, poor performance, and may lead to engine stalling or no-start conditions.
1. Most Common Causes
- Faulty or worn crankshaft position (CKP) or camshaft position (CMP) sensor
- Damaged, corroded, or loose wiring/connections in the high-resolution signal circuit
- Electromagnetic interference (EMI) affecting the wiring harness
- Damaged crankshaft or camshaft reluctor wheel with worn or missing teeth (for inductive or Hall-effect sensors)
- Internal ECM/PCM failure in the signal conditioning circuit
- Weak battery or charging system with fluctuating voltage
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Engine misfire or rough idle
- Hard starting or stalling
- Reduced engine power or hesitation
3. Step-by-Step Diagnosis
Step 1: Scan for additional codes and freeze frame data to identify related issues.
Step 2: Visually inspect the wiring and connectors for the crankshaft/camshaft position sensor for damage, corrosion, or loose connections.
Step 3: Test the sensor's resistance and signal output using a multimeter or oscilloscope per manufacturer specifications.
Step 4: If sensor and wiring are okay, check for metal debris on the sensor tip or damage to the reluctor wheel.
Step 5: If all else fails, test the PCM for proper signal reception and consider reprogramming or replacement.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive with this code as it can cause stalling or no-start conditions, leading to unsafe driving situations.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for diagnosis and sensor replacement, but can be higher if wiring repairs or PCM replacement is needed.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.