What causes fault code P0388?

• Most likely: Faulty crankshaft position sensor (internal short) • Likely: Wiring harness damage (short to voltage) • Possible: Corroded or loose connector at the sensor • Rare: Damaged reluctor ring or internal ECU failure

Powertrain (Engine & Gearbox)Standard EOBD

P0388 - Crankshaft Position Sensor B Circuit High

Q: What are the symptoms of fault code P0388?

• Check engine light (MIL) illuminated • Engine hard to start or no-start condition • Engine stalling during operation • Rough idling or misfiring • Vehicle may enter 'Limp home' mode

Q: How do you fix fault code P0388?

STEP 1: Inspect the sensor connector for oil contamination, moisture, or corrosion. Clean as necessary. STEP 2: Inspect the wiring harness between the sensor and ECU. Use a multimeter to check for a short to voltage on the signal wire. STEP 3: Measure sensor resistance (if inductive, typically 500-1500 Ohms) or use an oscilloscope to check the waveform during cranking. Hall-effect sensors should pulse between approx 0.5V and 4.5V. STEP 4: If wiring is intact but the signal remains high during rotation, replace the crankshaft position sensor.

Last updated:1 February 2026

Related:Crankshaft Position Sensor (CKP), Engine Control Unit (ECU/ECM), Reluktansring, Camshaft Position Sensor (CMP)

System

Powertrain (Engine & Gearbox)

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P0300

Random or Multiple Cylinder Misfire Detected

P0301

Cylinder 1 Misfire Detected

P0302

Cylinder 2 Misfire Detected

P0303

Cylinder 3 Misfire Detected

Technical Description

P0388 stands for Crankshaft Position Sensor B Circuit High. This diagnostic trouble code (DTC) is set when the Engine Control Module (ECM) perceives a voltage signal from the crankshaft position sensor 'B' circuit that is higher than the expected range. This usually indicates a short to voltage in the signal wire or a lost ground connection. The sensor is vital for calculating engine RPM and precise timing for fuel injection and ignition.

Possible Causes

Faulty crankshaft position sensor (internal short)

Wiring harness damage (short to voltage)

Corroded or loose connector at the sensor

Damaged reluctor ring or internal ECU failure

Symptoms

Check engine light (MIL) illuminated

Engine hard to start or no-start condition

Engine stalling during operation

Rough idling or misfiring

Vehicle may enter 'Limp home' mode

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P0388 - Crankshaft Position Sensor B Circuit High

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P0388 - Crankshaft Position Sensor B Circuit High

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