P1A77 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 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.
Code P1A77 Description
What are the Possible Causes of the DTC P1A77?
- 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?
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 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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Information for Specific Makes
- P1A77 Buick — Starter/Generator Control Module Coolant Temperature Sensor 2 Circuit High Voltage
- P1A77 Cadillac — Starter/Generator Control Module Coolant Temperature Sensor 2 Circuit High Voltage
- P1A77 Chevrolet — Starter/Generator Control Module Coolant Temperature Sensor 2 Circuit High Voltage
- P1A77 GMC — Starter/Generator Control Module Coolant Temperature Sensor 2 Circuit High Voltage
- P1A77 Saturn — Starter/Generator Control Module Coolant Temperature Sensor 2 Circuit High Voltage
Frequently Asked Questions about P1A77 Code
1. What does the OBDII code P1A77 mean?
P1A77 indicates a high voltage issue in the Starter/Generator Control Module Coolant Temperature Sensor 2 circuit, which monitors the temperature of the coolant for the starter/generator system.
2. What are the common symptoms of code P1A77?
Symptoms may include engine overheating, reduced fuel efficiency, poor hybrid system performance, or the illumination of the check engine light.
3. What causes the P1A77 code to appear?
Common causes include a faulty coolant temperature sensor, damaged wiring or electrical connectors, a malfunctioning starter/generator control module, or low coolant levels.
4. Can I drive my car with the P1A77 code present?
It’s not recommended to drive with this code due to the risk of engine overheating or damage to the hybrid/electrical system.
5. How do you diagnose the P1A77 code?
Diagnosis involves scanning the system with an OBDII tool, inspecting the coolant temperature sensor wiring and connectors, and testing the sensor and related components for proper function.
6. How can I fix the P1A77 code?
Repairs may include replacing the coolant temperature sensor, repairing or replacing damaged wiring, ensuring proper coolant levels, or reprogramming the control module if necessary.
7. How much does it cost to fix the P1A77 code?
Repair costs depend on the issue but typically range from $100 to $300 for sensor replacement, with higher costs if the control module requires replacement or reprogramming.
8. Can low coolant levels trigger the P1A77 code?
Yes, low coolant levels can affect the sensor's readings and cause the code to be set.
9. Will resetting the check engine light fix the P1A77 code?
Resetting the light may temporarily clear the code, but the underlying issue must be resolved to prevent it from returning.
10. Is the P1A77 code specific to hybrid or electric vehicles?
Yes, this code is typically associated with hybrid or electric vehicles that use a starter/generator system with a dedicated cooling circuit.
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