Failed crankshaft position sensor 'B' (internal open circuit or short); Damaged or corroded wiring harness between the sensor and ECM; Loose, dirty, or disconnected electrical connector at the sensor; Shorted or open signal circuit due to chafed insulation or broken wire; Faulty ECM driver or internal circuit for the sensor input (rare); Metallic debris or incorrect air gap between the sensor and reluctor wheel; Aftermarket sensor with incorrect resistance or output characteristics

DTC codes / P03xx · Ignition system and misfire / P0388

P0388Crankshaft Position Sensor 'B' Circuit High

Q: What does code P0388 mean?

Crankshaft Position Sensor 'B' Circuit High. P0388 indicates that the engine control module (ECM) has detected an abnormally high voltage on the crankshaft position sensor 'B' circuit, which is often the second crank sensor in systems that use two for redundancy or a specific signal path. The ECM expects the sensor's signal voltage to stay within a calibrated range, and a high reading means the circuit is open, shorted to power, or the sensor itself has failed.

P0388 indicates that the engine control module (ECM) has detected an abnormally high voltage on the crankshaft position sensor 'B' circuit, which is often the second crank sensor in systems that use two for redundancy or a specific signal path. The ECM expects the sensor's signal voltage to stay within a calibrated range, and a high reading means the circuit is open, shorted to power, or the sensor itself has failed.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaIgnition system and misfire

Symptoms you may notice

Illumination of the check engine light, often with no other noticeable symptoms
Intermittent or complete engine stall, especially when the engine is hot or under load
Difficulty starting or a no-start condition because the ECM cannot determine crankshaft position
Rough running, misfiring, or loss of power due to incorrect ignition and fuel timing
A tachometer that reads zero or fluctuates erratically while the engine is running

Common causes, most likely first

Failed crankshaft position sensor 'B' (internal open circuit or short)
Damaged or corroded wiring harness between the sensor and ECM
Loose, dirty, or disconnected electrical connector at the sensor
Shorted or open signal circuit due to chafed insulation or broken wire
Faulty ECM driver or internal circuit for the sensor input (rare)
Metallic debris or incorrect air gap between the sensor and reluctor wheel
Aftermarket sensor with incorrect resistance or output characteristics

How to diagnose and fix it

Perform a visual inspection of the sensor, connector, and wiring for obvious damage or corrosion
Use a scan tool to check for related codes and freeze-frame data to confirm the fault condition
Measure the sensor's resistance and compare it to the manufacturer's specification
Back-probe the sensor connector and check for reference voltage and ground with the key on
Inspect the signal wire for continuity and shorts to power or ground using a multimeter
Replace the crankshaft position sensor 'B' if electrical tests indicate an internal fault
Clear the codes and verify the repair with a test drive, ensuring the code does not return

What a high voltage on crank sensor B really means

A high voltage code often results from an open circuit rather than a shorted sensor, so check connector pins and wire continuity before condemning the sensor.
On some engines, sensor 'B' is a redundant crank sensor used for misfire detection or stop-start systems, so a failure may not cause a no-start but can disable those functions.
Metallic debris on the sensor tip or a damaged reluctor wheel can produce a high-voltage signal that mimics an electrical fault, so always inspect the sensor mounting area.
Aftermarket sensors with incorrect internal resistance are a common cause of repeat P0388 codes, and installing an OEM-quality part is often the permanent fix.
The ECM may set P0388 intermittently if the sensor signal is disrupted by a poor ground connection at the engine block, which is easy to overlook.

Can I keep driving with P0388?

If the engine starts and runs normally, you can drive cautiously to a repair shop, but avoid heavy acceleration or long trips because the fault can cause sudden stalling. If the engine stalls, misfires badly, or fails to start, stop driving and have the vehicle towed to prevent safety risks.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.