AutoCodes – Generic – P1A78

P1A78 Code - Starter/Generator Control Module Coolant Temperature Sensor 3 Performance

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: P1A78 indicates Starter/Generator Control Module Coolant Temperature Sensor 3 Performance.
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 2,339

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 P1A78 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 P1A78 - Starter/Generator Control Module Coolant Temperature Sensor 3 Performance - AutoCodes.com — P1A78 Code - Starter/Generator Control Module Coolant Temperature Sensor 3 Performance

What does this mean?

What are the Possible Causes of the DTC P1A78?

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 P1A78?

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 P1A78 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 P1A78 code?

Need more information on how to fix the P1A78 code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P1A78 code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

P1A78 Buick — Starter/Generator Control Module Coolant Temperature Sensor 3 Performance
P1A78 Cadillac — Starter/Generator Control Module Coolant Temperature Sensor 3 Performance
P1A78 Chevrolet — Starter/Generator Control Module Coolant Temperature Sensor 3 Performance
P1A78 GMC — Starter/Generator Control Module Coolant Temperature Sensor 3 Performance
P1A78 Saturn — Starter/Generator Control Module Coolant Temperature Sensor 3 Performance

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 P1A78 Code

1. What are the common symptoms of OBDII code P1A78?

- Common symptoms of this code may include engine overheating, poor vehicle performance, and issues with starting the vehicle.

2. What does the Starter/Generator Control Module Coolant Temperature Sensor 3 do?

- The sensor monitors the coolant temperature to ensure the engine operates within the optimal temperature range.

3. What are the possible causes of OBDII code P1A78?

- Potential causes of this code include a faulty coolant temperature sensor, wiring issues, or problems with the control module itself.

4. How can I diagnose the cause of OBDII code P1A78?

- Diagnosing this code typically involves testing the coolant temperature sensor, checking the wiring for any damage, and inspecting the control module for faults.

5. Can I still drive my vehicle with code P1A78 present?

- It is not recommended to drive your vehicle with this code present, as it can lead to further damage and potential safety hazards.

6. How is OBDII code P1A78 typically repaired?

- Repairing this code often involves replacing the faulty coolant temperature sensor, repairing any damaged wiring, or addressing issues with the control module.

7. Is it possible to clear OBDII code P1A78 without making repairs?

- Clearing the code without addressing the underlying issue is not recommended, as it will likely return once the problem persists.

8. Can a DIY enthusiast repair OBDII code P1A78 at home?

- Depending on your skill level and access to tools, some DIY enthusiasts may be able to address this code at home by following repair guides or consulting with a professional.

9. How important is it to address OBDII code P1A78 promptly?

- It is crucial to address this code promptly to prevent further damage to your vehicle and ensure its safe operation.

10. Are there any preventive maintenance steps to avoid OBDII code P1A78 in the future?

- Regularly checking and maintaining your vehicle's cooling system, including the coolant temperature sensor, can help prevent issues that may trigger this code.