Powertrain
Generic/SAE
OBD-II Fault Code
P0378: Timing Reference High Resolution Signal B Intermittent/Erratic Pulses
Meaning, symptoms, likely causes, diagnostic checks and repair guidance for P0378.
Engine timing / position
Use this category to narrow your checks before replacing parts.
High
Severity is a general guide. Confirm with scan-tool data and vehicle symptoms.
What P0378 usually means
Timing Reference High Resolution Signal B Intermittent/Erratic Pulses.
Common symptoms
Check Engine light; Poor drivability or reduced fuel economy depending on fault; No-start, rough running, limp mode or poor power possible
Likely causes
Faulty cam/crank sensor; Oil level/quality issue; VVT solenoid fault; Timing chain/belt issue; Wiring fault; High signal voltage; Open ground; Short to voltage; Failed sensor; Loose connector; Moisture/corrosion; Harness vibration fault
Diagnostic checks
Scan all modules and record freeze-frame data before clearing codes; Check battery voltage and related fuses; Check oil level/condition; Inspect sensor/solenoid connectors; Compare cam/crank correlation with scan data; Check sensor ground and signal circuit for short to voltage; Wiggle-test harness while watching live data; Inspect for water intrusion/corrosion
Repair guidance
Repair wiring or replace confirmed failed sensor/solenoid; Investigate mechanical timing if correlation faults remain; Repair ground/signal circuit or replace confirmed faulty sensor; Clean/secure connector and repair damaged harness
Verification after repair
Clear code, road-test through the same drive condition, then rescan