P0378 — Timing Reference High Resolution Signal B Too Few Pulses
Drive with caution — fix soon.
What P0378 means
This code means the engine control module is counting fewer high-resolution timing pulses than expected from the 'B' reference sensor, usually a crankshaft or camshaft position sensor. It typically points to a failing sensor, damaged wiring or connector, or worn or damaged teeth on the reluctor ring. It's usually fixable by replacing the sensor or repairing the circuit, without major engine work.
Common symptoms
- Check engine light is on
- Engine hesitates or stumbles while driving
- Hard starting or longer cranking
- Rough idle or slight engine shaking
- Occasional stalling
Common causes
- Failing crankshaft or camshaft position sensor (B)
- Damaged or corroded sensor wiring or connector
- Worn or damaged reluctor/tone ring teeth
- Excessive air gap between sensor and ring
- Faulty engine control module (rare)
Typical repair cost
$150 – $450
Varies by vehicle and root cause.
Frequently asked questions
Can I keep driving with a P0378 code?
For short trips, usually yes, but you shouldn't rely on it. If the engine stumbles or is hard to start, get it checked promptly to avoid being stranded.
How much does it cost to fix a P0378 code?
Most repairs run between $150 and $450. A simple sensor replacement is on the lower end, while wiring or reluctor ring repairs cost more.
Is a P0378 code serious?
It's moderately serious. It won't usually damage your engine, but it can cause poor running and stalling, so it's best to address it soon.
What does 'too few pulses' mean for P0378?
It means the 'B' timing sensor is sending fewer signal pulses than the computer expects per engine revolution, often from a worn sensor, bad wiring, or damaged trigger wheel teeth.