P0377 Code Meaning and Next Steps

First checks take 10 minutes for basic checks. No special tools are usually needed for the first checks.

Can you keep driving?

Stop driving if any of these apply

!The check-engine light is flashing or the engine is shaking badly.
!The vehicle is stalling, struggling to accelerate, or obviously running rough.

If the light is steady and the vehicle still drives normally: Maybe, but only for a very short distance if the engine still runs smoothly.

What to check first

Step-by-step checks

1
Free - no tools
Check whether the engine runs rough, stalls, or has starting trouble at the same time
2
Free - no tools
Inspect the timing sensor connector and harness for looseness or heat damage
3
Basic tool needed
Look for metal debris near the sensor or signs of a damaged target wheel
4
Basic tool needed
If scan data is available, compare reference signal behavior with engine RPM
5
Basic tool needed
Check whether the code appeared after timing work or sensor replacement

If the code returns

-If the pulse pattern is wrong at the sensor, the sensor or target wheel becomes more likely.
-If the signal is noisy only under vibration, the wiring path is a stronger suspect.
-If the code returns after connector repair, recheck sensor gap and mounting.

Background

What this code means

P0377 is a generic OBD-II code for a timing reference high-resolution signal that has too few pulses.

The engine controller expects a stable reference pattern. If the signal is missing pulses, the sensor, wiring, or target wheel may be the issue.

Diagnosis

Common causes

Most common

Faulty timing sensor

The sensor may be missing pulses or reading the pattern poorly.

Common

Damaged tone wheel or target wheel

The reference pattern may be physically distorted.

Common

Wiring or connector fault

A poor connection can make pulses disappear.

Possible

Metal debris near the sensor

Debris can interfere with the signal pattern.

Avoid these mistakes

What not to do

xDo not replace the ECU first if the sensor or target wheel is visibly damaged.
xDo not ignore starting or stalling symptoms that line up with the timing signal fault.

Parts

Parts that may need replacing

PartTypical costNotes

Timing sensor$40-$180Worth checking when the pulse pattern is missing data.

Connector or wiring repair$50-$250Useful when the signal is contaminated or intermittent.

Target wheel or reluctor repair$200-$900Relevant when the reference pattern is mechanically damaged.

Related OBD codes

P0376

P0376 means the engine timing reference high-resolution signal has too many pulses.

P0378

P0378 means the engine timing reference high-resolution signal is intermittent or erratic.

P0379

P0379 means the engine timing reference high-resolution signal has no pulses.

Source notes

Generic OBD-II (SAE J1979 / ISO 15031-5). P0377 was seeded from dtcdb and then expanded around timing reference pulse count faults, with emphasis on sensor, wiring, and target-wheel checks.

This guide is written as a generic multi-make reference, so bulletin history, sensor locations, and repair order can still change by manufacturer and engine family.

This is generic OBD-II guidance and should not override vehicle-specific service information. Exact diagnosis and repair steps vary by make, engine family, and model year.

Last reviewed: 2026-04-10

Reference: Open reference

P0377 - The Engine Timing Reference High-resolution Signal Has Too Few Pulses