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 a crankshaft or camshaft position sensor and is used for precise fuel injection and ignition timing. Erratic pulses can cause misfires, poor performance, and may prevent the engine from starting. Common causes include a faulty sensor, damaged wiring, or issues with the reluctor wheel.
01. Most Common Causes
- Faulty crankshaft or camshaft position sensor
- Damaged or corroded wiring/connectors
- Magnetic debris on the sensor or reluctor wheel
- Damaged reluctor wheel (missing teeth or cracks)
02. Symptoms You Will Notice
- Engine misfire or rough running
- Hard starting or no start condition
- Check Engine Light illuminated
- Reduced engine power or stalling
03. Step-by-Step Diagnosis
Step 1: Scan for additional codes and record freeze frame data.
Step 2: Visually inspect the sensor and wiring for damage or corrosion.
Step 3: Test sensor resistance and AC voltage output with a multimeter while cranking.
Step 4: Check reluctor wheel for damage or debris using a borescope if necessary.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
No, it is not safe. The erratic signal can cause engine misfires, stalling, or no start, which may lead to an accident or further engine damage.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for a DIY sensor replacement, or $150 to $400 if professionally diagnosed and repaired, depending on labor rates and parts.