AutoCodes – Chevrolet – P1A77 Chevrolet

P1A77 Chevrolet Code - Starter/Generator Control Module Coolant Temperature Sensor 2 Circuit High Voltage

Quick Answer

The Starter/Generator Control Module (SGCM) monitors its internal fluid temperature sensors to control the SGCM coolant pump and SGCM cooling fan. Common causes include Faulty Starter/Generator Control Module (SGCM), Starter/Generator Control Module (SGCM) harness is open or shorted, Starter/Generator Control Module (SGCM) 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: P1A77 Chevrolet indicates Starter/Generator Control Module Coolant Temperature Sensor 2 Circuit High Voltage.
Common causes: Common causes include Faulty Starter/Generator Control Module (SGCM), Starter/Generator Control Module (SGCM) harness is open or shorted, Starter/Generator Control Module (SGCM) 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 1,077

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 Feb 22, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P1A77 Chevrolet Description

The Starter/Generator Control Module (SGCM) monitors its internal fluid temperature sensors to control the SGCM coolant pump and SGCM cooling fan. The internal fluid temperature sensors of the SGCM are thermistors and are not serviceable. When the internal fluid temperatures are cold, the resistances of the sensors are high and the voltage signals are high. When the internal fluid temperatures are hot, the resistances of the sensors are low and the voltage signals are low. The input parameters are not displayed on the scan tool.

OBDII Code P1A77 Chevrolet - Starter/Generator Control Module Coolant Temperature Sensor 2 Circuit High Voltage - AutoCodes.com — P1A77 Chevrolet Code - Starter/Generator Control Module Coolant Temperature Sensor 2 Circuit High Voltage

What does this mean?

What are the Possible Causes of the DTC P1A77 Chevrolet?

Faulty Starter/Generator Control Module (SGCM)
Starter/Generator Control Module (SGCM) harness is open or shorted
Starter/Generator Control Module (SGCM) circuit poor electrical connection

How to Fix the DTC P1A77 Chevrolet?

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 P1A77 Chevrolet 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.

Frequently Asked Questions about P1A77 Chevrolet Code

1. What are common symptoms of OBDII code P1A77 in a Chevrolet related to the Starter/Generator Control Module Coolant Temperature Sensor 2 Circuit High Voltage issue?

- Common symptoms include engine overheating, poor fuel efficiency, and potential issues with the vehicle's starting and charging system.

2. What are the possible causes of OBDII code P1A77 in a Chevrolet indicating a problem with the Coolant Temperature Sensor 2 Circuit High Voltage?

- The possible causes may include a faulty coolant temperature sensor, issues with the wiring or connectors associated with the sensor, or a malfunctioning Starter/Generator Control Module.

3. How can I diagnose the OBDII code P1A77 related to the Coolant Temperature Sensor 2 Circuit High Voltage problem in my Chevrolet?

- You can use an OBDII scanner to retrieve the specific error code, visually inspect the sensor and its wiring for any visible damage, and perform electrical tests to check for proper sensor functionality.

4. What are some repair tips for addressing the Starter/Generator Control Module Coolant Temperature Sensor 2 Circuit High Voltage issue in a Chevrolet?

- Repair tips may include replacing the faulty coolant temperature sensor, repairing any damaged wiring or connectors, or reprogramming the Starter/Generator Control Module if necessary.

5. Is it safe to continue driving my Chevrolet with the OBDII code P1A77 related to the Coolant Temperature Sensor 2 Circuit High Voltage problem?

- It is not recommended to drive the vehicle with this issue as it can lead to engine overheating and potential damage to other components. It is best to address the problem promptly.

6. Can I reset the OBDII code P1A77 in my Chevrolet related to the Coolant Temperature Sensor 2 Circuit High Voltage issue by disconnecting the battery?

- While disconnecting the battery may clear the code temporarily, it is important to diagnose and repair the underlying issue causing the code to prevent it from reoccurring.

7. How much does it typically cost to repair the Starter/Generator Control Module Coolant Temperature Sensor 2 Circuit High Voltage problem in a Chevrolet?

- The cost of repair can vary depending on the exact cause of the issue, but it may involve replacing the coolant temperature sensor, repairing wiring, or reprogramming the control module. Costs can range from a few hundred to over a thousand dollars.

8. Are there any recalls or technical service bulletins (TSBs) related to OBDII code P1A77 in Chevrolet vehicles with Coolant Temperature Sensor 2 Circuit High Voltage issues?

- It is recommended to check with a Chevrolet dealership or visit the National Highway Traffic Safety Administration (NHTSA) website to see if there are any relevant recalls or TSBs related to this specific problem.

9. Can a DIY enthusiast with basic automotive knowledge repair the OBDII code P1A77 related to the Coolant Temperature Sensor 2 Circuit High Voltage issue in a Chevrolet?

- While some basic repairs like sensor replacement or wiring checks can be done by DIY enthusiasts, complex diagnostics and module reprogramming may require specialized tools and expertise, so professional help may be necessary.

10. How often should I check the Coolant Temperature Sensor and related components in my Chevrolet to prevent issues like OBDII code P1A77 from occurring?

- It is recommended to include regular coolant system maintenance in your vehicle's service schedule, which may include checking the coolant temperature sensor and associated wiring during routine inspections or when experiencing any symptoms of potential problems.