Fault codeP0387

Crankshaft Position Sensor B Circuit Low Input

What this code means

Crankshaft Position Sensor B Circuit Low Input.

P0387 is a generic code: it means the same thing on every make. P0387 belongs to family P03xx — Ignition and misfire. Its page explains how to read a code and groups all its codes by part.

Type of fault

The control unit reads a voltage on this circuit below its expected range. Usual causes: a wire shorted to ground or broken, a corroded or loose connector, or the component itself. Check the wiring and connector before replacing the part — that is where many of these faults turn out to be.

Crankshaft position sensor (engine speed)

The crankshaft sensor faces a toothed wheel on the crankshaft or flywheel and counts its teeth as they pass. From that signal the control unit knows the engine speed and the exact position of the pistons: it is the reference for all ignition and injection timing.

What you notice

Without this signal the engine cannot run. A failing sensor typically causes a sudden stall, often when hot, or an engine that cranks but will not start; the rev counter may drop to zero while driving.

How to check it

Look at the connector and the wiring near the gearbox or the crankshaft pulley, where it is exposed to heat and dirt. Clean metal debris off the sensor tip, and check the toothed wheel for missing or damaged teeth. If the engine still runs, Klaro's rev reading dropping out at the moment of a stutter is a strong clue.

Watch it live in Klaro

With an OBD2 adapter plugged in, these live readings show the part at work, when your car reports them:

• Engine RPM
• Timing advance

What to do

Have it checked promptly. A misfire sends unburnt fuel into the exhaust and destroys the catalytic converter within a few dozen kilometres. If the light is flashing, stop driving.

How to read this code

• PPowertrain
• 0standardised code
• 3Ignition and misfire
• 87P0387

Other codes for the same part

• P0372Timing Reference High Resolution Signal A Too Few Pulses
• P0373Timing Reference High Resolution Signal A Intermittent/Erratic Pulses
• P0374Timing Reference High Resolution Signal A No Pulses
• P0375Timing Reference High Resolution Signal B Malfunction
• P0376Timing Reference High Resolution Signal B Too Many Pulses
• P0377Timing Reference High Resolution Signal B Too Few Pulses
• P0378Timing Reference High Resolution Signal B Intermittent/Erratic Pulses
• P0379Timing Reference High Resolution Signal B No Pulses
• P0385Crankshaft Position Sensor B Circuit Malfunction
• P0386Crankshaft Position Sensor B Circuit Range/Performance
• P0388Crankshaft Position Sensor B Circuit High Input
• P0389Crankshaft Position Sensor B Circuit Intermittent