AutoCodes – Generic – P077A

P077A Code - Output Speed Sensor Circuit - Loss of Direction Signal

Quick Answer

The speed sensor detects the revolution of the idler gear parking pawl lock gear and emits a pulse signal. Common causes include Faulty Speed Sensor, Speed Sensor harness is open or shorted, Speed 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: P077A indicates Output Speed Sensor Circuit - Loss of Direction Signal.
Common causes: Common causes include Faulty Speed Sensor, Speed Sensor harness is open or shorted, Speed 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 2,102

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Jan 26, 2019

Description
Possible Causes
How To Fix
Cost to Diagnose
Comments
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Code P077A Description

The speed sensor detects the revolution of the idler gear parking pawl lock gear and emits a pulse signal. The pulse signal is sent to the Transmission Control Module (TCM) which converts it into vehicle speed.

OBDII Code P077A - Output Speed Sensor Circuit - Loss of Direction Signal - AutoCodes.com — P077A Code - Output Speed Sensor Circuit - Loss of Direction Signal

What does this mean?

What are the Possible Causes of the DTC P077A?

Faulty Speed Sensor
Speed Sensor harness is open or shorted
Speed Sensor circuit poor electrical connection

How to Fix the DTC P077A?

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 P077A 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.

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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.