What are the common causes of P0379?

An open in the signal B circuit. A dead signal B sensor. A broken signal B tone ring. No reference voltage or ground at the signal B sensor. An ECM that lost the signal B input.

Check for signal B at the ECM with a scope while cranking. Test the signal B sensor for reference voltage and ground. Measure the signal B sensor resistance. Inspect the signal B tone ring for damage. Replace the signal B sensor if it is dead. Clear the code and retest.

P0379

Timing Reference High Resolution Signal B No Pulses

System: Ignition and misfire (P code)
Lamp: Check Engine Light
Category: Powertrain - Ignition

What it means

P0379 means Timing Reference High Resolution Signal B No Pulses.

Check these first

An open in the signal B circuit
A dead signal B sensor
A broken signal B tone ring
No reference voltage or ground at the signal B sensor
An ECM that lost the signal B input

What to do next

Check for signal B at the ECM with a scope while cranking
Test the signal B sensor for reference voltage and ground
Measure the signal B sensor resistance
Inspect the signal B tone ring for damage
Replace the signal B sensor if it is dead
Clear the code and retest

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Updated

Generic SAE J2012 definition. Last updated 2026-10-10.