P0388
Crankshaft Position Sensor B Circuit High Input
If your code reader dashboard displays the generic DTC error code P0388, your vehicle is currently experiencing an active failure related to "Crankshaft Position Sensor B Circuit High Input". Proper system troubleshooting is required to safely clear this warning.
Driver's Summary
Storing code P0388 is your car's way of telling you something is wrong with the crankshaft position sensor b circuit high input. In practice, this fault causes no start condition, engine misfires. This is a serious fault — avoid extended driving and have your vehicle inspected by a mechanic as soon as possible to prevent further damage.
Symptoms
No start condition, engine misfires
Common Causes
- Short to battery voltage in sensor B circuit
- Open ground connection
- Failed crank sensor B
- Bad PCM
How to Fix
- 1 Fix short to power
- 2 Repair ground wire
- 3 Replace crankshaft sensor B
- 4 Test PCM
Technical Explanation
The ECM detects code P0388 by continuously monitoring the relevant sensor circuit against calibrated threshold values stored in its non-volatile memory. The PCM monitors crankshaft rotational velocity via the CKP sensor at a resolution of individual tooth gaps on the reluctor ring. A combustion event in each cylinder produces a measurable acceleration spike; its absence or weakness is flagged as a misfire event within a 200-revolution or 1000-revolution test window. The fault remains stored in memory even after the MIL is cleared; it becomes a confirmed DTC after failing two consecutive drive cycles, and the PCM logs a freeze frame record of the engine's exact operating state at the moment of detection.
Is It Safe to Drive?
With P0388 active, your engine or transmission is not operating within design parameters. Short-term driving may seem fine, but internal damage is accumulating — particularly to short to battery voltage in sensor b circuit.
Mechanic's Pro Tip
Module replacement should always be the last resort for P0388 after exhaustively verifying all power supply circuits, ground connections, and communication bus wiring. Use a wiring diagram to locate all fuses, relays, and ground points for the affected module, and measure voltage drop on each ground with the circuit loaded. A module "failure" is frequently a corroded ground eyelet or a weak battery causing brownout conditions — fix these first and you'll save hundreds of dollars on an unnecessary module replacement.
Sensor replacement: 150 - 350