P0128 GMC Code - Engine Coolant Temperature Below Thermostat Regulating Temperature
Quick Answer
The Engine Control Module (ECM) monitors the temperature of the engine coolant for engine control and as enabling criteria for some diagnostics. Common causes include Leaking or stuck open thermostat, Low engine coolant level, Insufficient warm-up time. 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
- P0128 GMC indicates Engine Coolant Temperature Below Thermostat Regulating Temperature.
- Common causes
- Common causes include Leaking or stuck open thermostat, Low engine coolant level, Insufficient warm-up time.
- 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 P0128 GMC Description
What are the Possible Causes of the DTC P0128 GMC?
- Leaking or stuck open thermostat
- Low engine coolant level
- Insufficient warm-up time
- Faulty Engine Coolant Temperature (ECT) sensor
- Engine Coolant Temperature sensor harness is open or shorted
- Engine Coolant Temperature sensor electrical circuit poor connection
How to Fix the DTC P0128 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.
Code Tech Notes
What is the Cost to Diagnose the Code?
Labor: 1.0
To diagnose the P0128 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 P0128 GMC code?
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Need Help with the Code?
Get the P0128 GMC code diagnosed by a professional: Find a repair shop in your area
Information for Specific GMC Models
- P0128 2014 GMC Sierra — Engine Coolant Temperature Below Thermostat Regulating Temperature
- P0128 2015 GMC Sierra — Engine Coolant Temperature Below Thermostat Regulating Temperature
- P0128 2016 GMC Sierra — Engine Coolant Temperature Below Thermostat Regulating Temperature
- P0128 2017 GMC Sierra — Engine Coolant Temperature Below Thermostat Regulating Temperature
- P0128 2018 GMC Sierra — Engine Coolant Temperature Below Thermostat Regulating Temperature
Frequently Asked Questions about P0128 GMC Code
1. What are the common symptoms of OBDII code P0128 in a GMC vehicle?
- Common symptoms include the engine running colder than normal, poor fuel economy, and the Check Engine light being illuminated.
2. What typically causes the OBDII code P0128 in a GMC vehicle?
- The most common cause is a malfunctioning thermostat, which fails to regulate the engine coolant temperature properly.
3. How serious is the OBDII code P0128 in a GMC vehicle?
- While it may not cause immediate harm to the vehicle, it can lead to reduced fuel efficiency, increased emissions, and potential damage to the engine over time.
4. Can a faulty coolant temperature sensor trigger the OBDII code P0128 in a GMC vehicle?
- Yes, a faulty coolant temperature sensor can sometimes be the cause of the P0128 code, as it may provide incorrect temperature readings to the engine control module.
5. What are some DIY repair tips for resolving the OBDII code P0128 in a GMC vehicle?
- DIY repair tips include checking and replacing the thermostat, ensuring proper coolant levels, and inspecting the cooling system for leaks or blockages.
6. How can a mechanic diagnose the OBDII code P0128 in a GMC vehicle?
- A mechanic can use a scan tool to read the code, test the thermostat for proper operation, check the coolant temperature sensor, and inspect the cooling system components.
7. Is it safe to continue driving with the OBDII code P0128 in a GMC vehicle?
- It is generally safe to drive with the P0128 code, but it is recommended to address the issue promptly to prevent potential engine damage and ensure optimal vehicle performance.
8. Will resetting the Check Engine light resolve the OBDII code P0128 in a GMC vehicle?
- Resetting the Check Engine light may temporarily turn it off, but it will not fix the underlying issue causing the P0128 code. The problem should be diagnosed and repaired.
9. How much does it typically cost to repair the OBDII code P0128 in a GMC vehicle at a mechanic or dealership?
- Repair costs can vary depending on the exact cause of the issue, but the average range is between $150 to $400 for parts and labor.
10. Can a clogged radiator or cooling system cause the OBDII code P0128 in a GMC vehicle?
- Yes, a clogged radiator or cooling system can restrict the flow of coolant and lead to improper temperature regulation, triggering the P0128 code.
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