Drive with caution — fix soon.
This code means the engine computer isn't receiving any pulses from the high-resolution timing reference signal (B), which it relies on for precise crankshaft or camshaft position and timing. It's usually caused by a failing timing reference sensor, damaged wiring or connectors, a poor ground, or a problem with the reluctor/tone ring. It's typically fixable by replacing the sensor or repairing the circuit.
$150 – $500
Varies by vehicle and root cause.
For short trips usually yes, but don't rely on it. This timing reference signal is critical to engine timing, and if it drops out completely the engine can stall or fail to start, so get it checked promptly.
Most repairs land between $150 and $500. A wiring or connector repair is on the low end, while replacing the timing reference sensor with labor pushes toward the higher end.
It's moderate but worth taking seriously. The engine may run for now, but a missing timing reference signal can cause sudden stalling or a no-start, which is why prompt repair is recommended.
It means the computer expected a stream of timing pulses from the high-resolution reference sensor but received none. That usually points to a dead sensor, a broken wire, or a damaged tone ring rather than just a weak signal.