AutoCodes – GMC – P1377 GMC

P1377 GMC Code - Ignition Control Module Cam Ref Pulse To 4X Ref Pulse Incorrect

Quick Answer

The Powertrain Control Module (PCM) has detected an incorrect number of 4X pulses compared to the cam reference- 4X signal is lost. Common causes include Faulty 4X Crankshaft Position (CKP) Sensor, 4X Crankshaft Position (CKP) Sensor harness is open or shorted, 4X Crankshaft Position (CKP) Sensor circuit poor electrical connection. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means: P1377 GMC indicates Ignition Control Module Cam Ref Pulse To 4X Ref Pulse Incorrect.
Common causes: Common causes include Faulty 4X Crankshaft Position (CKP) Sensor, 4X Crankshaft Position (CKP) Sensor harness is open or shorted, 4X Crankshaft Position (CKP) Sensor circuit poor electrical connection.
Severity: High - diagnose this code as soon as possible.
Can I drive?: Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

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Code Popularity 3,113

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Intermediate (2 / 3)

What is this?

Table of contents Created and updated by William Orellana on Aug 16, 2019

Description
Possible Causes
How To Fix
Cost to Diagnose
Comments
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Code P1377 GMC Description

The Powertrain Control Module (PCM) has detected an incorrect number of 4X pulses compared to the cam reference- 4X signal is lost.

OBDII Code P1377 GMC - Ignition Control Module Cam Ref Pulse To 4X Ref Pulse Incorrect - AutoCodes.com — P1377 GMC Code - Ignition Control Module Cam Ref Pulse To 4X Ref Pulse Incorrect

What does this mean?

What are the Possible Causes of the DTC P1377 GMC?

Faulty 4X Crankshaft Position (CKP) Sensor
4X Crankshaft Position (CKP) Sensor harness is open or shorted
4X Crankshaft Position (CKP) Sensor circuit poor electrical connection

How to Fix the DTC P1377 GMC?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P1377 GMC code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

Need more information about the P1377 GMC code?

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About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.