What it means
Timing reference signal B delivers fewer pulses per crank revolution than expected — broken reluctor teeth, sensor air gap too wide, or tone wheel chipped.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The engine control module counts timing reference signal B pulses to track crankshaft rotation. This code sets when fewer pulses arrive per crank revolution than expected, which can happen if tone-wheel teeth are damaged or missing, the sensor gap is excessive, or the sensor or wiring is faulty.
Common causes
Most likely first.
- Damaged or missing tone-wheel teeth
- Excessive sensor-to-wheel gap
- Faulty timing reference sensor or wiring
Symptoms
- Check engine light on
- Hard starting or no start
- Engine stalling or rough running
- Power loss
How to diagnose it
- Save freeze-frame data and check live engine-speed data during cranking to see whether signal B drops out or appears unusually weak.
- Locate signal B using the wiring diagram, then inspect its connector and wiring for disconnection, corrosion, damage, or a poor fit.
- Check the signal B sensor mounting and measure its gap to the tone wheel against the manufacturer's specification.
- Inspect the tone wheel for chipped, bent, or missing teeth and verify that it is the correct part and properly aligned.
- Test signal B's circuit and waveform during cranking against the manufacturer's specification to separate a sensor or wiring fault from a damaged target.
Common fixes
- Reconnect or clean a loose or corroded signal B connector.
- Repair damaged signal B wiring.
- Correct the sensor mounting or air gap to the manufacturer's specification.
- Replace the faulty signal B sensor or repair the damaged tone wheel, as confirmed by testing.
Can I keep driving?
If the engine is stalling, hard to start, or losing power, avoid driving in traffic or at high speed because it may stall again. Continued operation with unreliable timing information can worsen drivability and leave you unable to restart.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.