2021 Mercedes-Benz AMG GT P012800 Coolant Temperature TSB

Owners of the 2021 Mercedes-Benz AMG GT may experience a Check Engine Light (CEL) illuminating on their dashboard. This often corresponds to diagnostic trouble code (DTC) P012800, which specifically indicates that "The Coolant Temperature is Below the Specified Temperature."

This issue has been documented by Mercedes-Benz in Technical Service Bulletin (TSB) LI20.10-P-072886, which applies to vehicles equipped with M176, M177, and M178 engines. The TSB provides guidance for technicians on how to diagnose and address the underlying cause of the P012800 code.

Symptoms

The primary symptom an owner will notice is the illumination of the Check Engine Light (CEL) on the instrument cluster. This is typically triggered by the engine management system detecting an abnormal coolant temperature condition.

Specifically, the TSB notes the symptom as "Power generation > Engine management > Indicator lamp > Engine diagnosis > lit," which refers to the Check Engine Light being active due to an engine diagnostic fault.

Fault Codes / DTCs

The specific diagnostic trouble code associated with this issue is:

• P012800: "The Coolant Temperature is Below the Specified Temperature"

This code indicates that the engine's coolant has not reached the expected operating temperature within a specified timeframe, or is consistently running cooler than it should. This can impact engine efficiency and emissions.

Cause of the Mercedes-Benz AMG GT P012800

According to Mercedes-Benz, the exact cause of the Mercedes-Benz AMG GT P012800 fault is currently "Under investigation." Despite being under investigation, the manufacturer has provided recommended measures to address the code.

Important Warnings

Mercedes-Benz explicitly states that this issue "is not an issue that affects drivability or performance and is not a safety concern." The vehicle remains safe to operate with this code.

However, the measures outlined in the "Remedy" section are strongly recommended to ensure proper engine function and to prevent potential long-term issues related to suboptimal operating temperatures. Owners should not ignore the Check Engine Light.

Repair Procedure Summary

The repair procedure outlined in TSB LI20.10-P-072886 focuses on checking for warranty coverage and then performing the necessary repairs, which often involve the engine thermostat. Technicians are instructed to follow these steps:

1. Check Emission Extended Warranty: Use the Vehicle Master Information (VMI) system to determine if the vehicle is covered under the Emission Extended Warranty for the engine thermostat, which includes potential software updates. This warranty may apply to various models and platforms from model years 2019-2023.
2. Follow NCU Instructions (if covered): If the vehicle is covered under the Emission Extended Warranty, the technician must perform the specific repair steps detailed in the New Control Unit (NCU) system. These instructions are proprietary to Mercedes-Benz and guide the technician through the repair process.
3. Refer to Attachments (if not covered): If the vehicle does not fall within the Emission Extended Warranty coverage, technicians are directed to consult the "Remedy Instructions" provided in the TSB's attachments. This attachment (LI20.10-P-072886 Remedy Instructions v2.docx) contains the detailed repair steps, which likely include replacing the thermostat and bleeding the coolant system, as indicated by WIS-Reference AR20.00-P-1142-04A.

Required Parts

Addressing the P012800 code often involves replacing the engine thermostat. The TSB lists the following relevant part numbers:

• A1772007901: Thermostat (for M177LS2, M177LSE engines)
• A1772008801: THERMOSTAT (for M176, M177LS1, M178 engines)

These parts are specified based on the particular engine variant installed in the vehicle.

Owner Action

If your 2021 Mercedes-Benz AMG GT displays a Check Engine Light with the DTC P012800, it is recommended to have your vehicle inspected by an authorized Mercedes-Benz service center. While the issue is not deemed a safety concern, addressing it promptly can help maintain optimal engine performance and efficiency.

Be sure to inquire about the Emission Extended Warranty coverage for the engine thermostat, as this could cover the cost of diagnosis and repair, including any necessary software updates.

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Source: NHTSA ID: 11027120