What does P0378 mean?

Timing Reference High Resolution Signal B Intermittent/Erratic Pulses May cause rough idle, loss of power, hesitation/stalling, can still run but performance degraded

AutoFixDB - Free OBD-II diagnostic trouble code lookup. Find causes, symptoms, diagnostic steps and repair solutions.

Overview

Generic OBD-II code indicating erratic or intermittent high‑resolution timing reference signal 'B' from position sensors affecting engine timing.

Common Symptoms

Check Engine Light illuminated
Rough idling or unstable engine operation
Loss of power or poor acceleration
Hard starting or intermittent stalling

Most Common Causes

Faulty crankshaft or camshaft position sensor 'B' high

Sensor degradation, heat exposure, contamination commonly lead to erratic signals

Wiring damage or connector issues high

Corroded pins, broken wires or poor connections disrupt signal integrity

Reluctor/tooth wheel damage or misalignment medium

Damaged tone ring or disturbed timing hardware may create irregular pulses

ECM internal fault low

Less common but possible; module front‑end circuitry may misinterpret signals

Diagnostic Steps

Retrieve code and live data using OBD‑II scanner

Expected: Presence of P0378 and any related codes

Interpretation: Confirms code is current and checks for multiple faults
Visually inspect sensor harness and connectors

Expected: No corrosion, breaks, loose connections

Interpretation: Faults here often cause erratic signal pulses
Test sensor output with multimeter (and oscilloscope if available)

Expected: Stable voltage fluctuation or square waveform during cranking

Interpretation: Erratic/absent waveform suggests sensor or wiring issue
Check reluctor ring or timing hardware condition

Expected: No broken or misaligned teeth

Interpretation: Mechanical timing issues can mimic sensor faults
Verify ECM power, ground and update software if applicable

Expected: Proper supply and ground, updated calibration

Interpretation: Ensures control module isn’t misreading the signal

Repair Solutions

Replace faulty position sensor medium

Estimated Cost: $100 - $300

Sensor cost varies by vehicle; accessible on many engines

Repair or replace damaged wiring/connectors medium

Estimated Cost: $50 - $250

Extent of wiring repair impacts cost

Correct or replace reluctor ring/timing components hard

Estimated Cost: $300 - $800

Involves disassembly; cost depends on engine design

ECM reprogram or replacement hard

Estimated Cost: $400 - $1500

Consider if all sensor and wiring checks clear

Common Misdiagnoses

Avoid these common diagnostic mistakes:

Assuming only camshaft sensor when crankshaft sensor also can trigger this code

Frequently Asked Questions

Can you explain the meaning of P0378?

Technically, the P0378 code represents Timing Reference High Resolution Signal B Intermittent/Erratic Pulses. It usually points to a fault within the Ignition.

Reflecting on severity: How bad is P0378?

This is a medium priority issue. May cause rough idle, loss of power, hesitation/stalling, can still run but performance degraded

Symptoms associated with DTC P0378

You may experience the following: Check Engine Light illuminated, Rough idling or unstable engine operation, Loss of power or poor acceleration.

Why is my car throwing a P0378 code?

The most common causes are: Faulty crankshaft or camshaft position sensor 'B', Wiring damage or connector issues, Reluctor/tooth wheel damage or misalignment.

Estimated repair costs for different causes of P0378

It depends on what needs to be fixed. Repair or replace damaged wiring/connectors repairs are cheaper (~$250), while ECM reprogram or replacement repairs are on the higher end (~$1500).

Does code P0378 apply to Toyota vehicles?

P0378 is not specific to any one brand. It can appear on Ford, Dodge, Toyota, Honda, Jeep, and other vehicles.

P0378: Timing Reference High Resolution Signal B Intermittent/Erratic Pulses