P0377 medium Severity

P0377: Timing Reference High Resolution Signal B Too Few Pulses

May cause rough idle, misfires, hard starting or loss of power; continued driving with the issue can lead to more serious engine performance issues

Overview

P0377 timing reference high resolution signal B too few pulses engine position sensor signal

Common Symptoms

  • Check Engine Light illuminated
  • Rough idle
  • Difficulty starting or no start
  • Loss of engine power or hesitation
  • Occasional engine stall

Most Common Causes

Faulty high-resolution timing reference sensor (e.g., crankshaft or camshaft position sensor signal B) high

Primary sensor that generates pulses may fail and produce too few signals for PCM

Damaged or corroded wiring/connectors in the timing reference B circuit high

Wiring harness faults can attenuate or interrupt pulse signals

PCM/ECM communication fault or software calibration issue medium

Control module may fail to register pulses even when sensor function is nominal

Mechanical timing component issues (e.g., stretched timing chain/belt or damaged reluctor ring) medium

Irregular timing disc movement can cause inconsistent pulse generation

Diagnostic Steps

  1. Connect OBD-II scanner and confirm code P0377 and any related codes
    Expected: Presence of P0377 and possible related cam/crank sensor codes
    Interpretation: Confirms code and checks for additional context
  2. Visually inspect sensor connectors and wiring associated with timing reference signal B
    Expected: No loose, corroded, or damaged connectors or broken wires
    Interpretation: If damage is found, repair wiring and clear code; if not, proceed
  3. Test sensor output using a multimeter or oscilloscope while cranking or running
    Expected: Clean, consistent square wave pulses or within specified voltage/resistance
    Interpretation: Weak or irregular waveform indicates sensor replacement
  4. Check continuity and proper reference voltage supply to the sensor circuit
    Expected: Continuity and correct reference voltage from PCM
    Interpretation: Open circuits or incorrect reference indicate wiring/PCM faults
  5. Inspect timing belt/chain components and reluctor ring alignment
    Expected: Proper alignment and condition of mechanical timing components
    Interpretation: Mechanical irregularities contributing to pulse issues require repair

Repair Solutions

Replace faulty high-resolution timing reference sensor medium
Estimated Cost: $150 - $300

Costs vary by sensor type and vehicle model

Repair or replace damaged wiring/connectors medium
Estimated Cost: $50 - $200

Depends on extent of wiring damage

Update or reprogram PCM/ECM software medium
Estimated Cost: $100 - $250

May resolve calibration mismatches

Repair/replace timing belt/chain or reluctor ring issues hard
Estimated Cost: $300 - $800

Mechanical timing repairs can be labor-intensive

Common Misdiagnoses

Avoid these common diagnostic mistakes:

  • Replacing only the crankshaft position sensor without checking wiring or PCM calibration

Frequently Asked Questions

What does the P0377 code mean?

Timing Reference High Resolution Signal B Too Few Pulses is the standard definition for P0377. This diagnostic code is triggered when the ECU detects a problem in the Ignition.

Reflecting on severity: How bad is P0377?

You should treat P0377 as a medium issue. May cause rough idle, misfires, hard starting or loss of power; continued driving with the issue can lead to more serious engine performance issues

What are the symptoms of P0377?

Common symptoms include: Check Engine Light illuminated, Rough idle, Difficulty starting or no start. You might also notice the Check Engine Light is on.

Why is my car throwing a P0377 code?

It can be caused by several factors, most notably: Faulty high-resolution timing reference sensor (e.g., crankshaft or camshaft position sensor signal B), Damaged or corroded wiring/connectors in the timing reference B circuit, PCM/ECM communication fault or software calibration issue.

What is the price difference for fixing P0377?

It depends on what needs to be fixed. Repair or replace damaged wiring/connectors repairs are cheaper (~$200), while Repair/replace timing belt/chain or reluctor ring issues repairs are on the higher end (~$800).

Is the P0377 code specific to Jeep?

Yes, P0377 is a generic code that applies to all OBD-II compliant vehicles, including Ford, Toyota, Honda, Chevrolet, Nissan, Dodge, BMW, and more.

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