P0388: Crankshaft Position Sensor B Circuit High Input
The P0388 code indicates that the Engine Control Module (ECM) has detected a voltage signal from the crankshaft position sensor B that is higher than the expected range. This sensor monitors the rotational speed and position of the crankshaft, which is critical for engine timing, fuel injection, and ignition. A high input can result from a faulty sensor, wiring issues, or electrical interference, potentially causing drivability problems.
01. Most Common Causes
- Faulty crankshaft position sensor B
- Short to voltage in sensor circuit
- Damaged wiring or connector
- ECM malfunction (rare)
02. Symptoms You Will Notice
- Engine may not start or stalls
- Check Engine Light illuminated
- Rough idle or misfires
- Reduced engine performance
03. Step-by-Step Diagnosis
Step 1: Use an OBD2 scanner to confirm P0388 and check for other codes.
Step 2: Visually inspect the sensor and wiring for damage, corrosion, or loose connections.
Step 3: Test sensor resistance and voltage with a multimeter; compare to manufacturer specs.
Step 4: Check for shorts to power or ground in the circuit.
Step 5: If sensor and wiring are okay, test ECM output signals.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
No, it is not safe. The engine may stall or fail to start, leading to a potential accident or being stranded.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for a sensor replacement, plus diagnostic fees if done by a shop.