Decoding the EOBD/OBDII P1299 Code: Cylinder Head Overtemperature Protection Active

Encountering an “Engine Coolant Overtemp” (ECO) warning on your dashboard can be unsettling, especially when accompanied by a “Check Engine Light” (MIL). For Ford Fusion owners, or drivers of any modern vehicle equipped with an OBDII system, these warnings can often be linked to specific diagnostic trouble codes (DTCs). One such code, P1299, signals a critical issue: “Cylinder head overtemperature protection active.”

This article delves into the Eobd/obdii P1299 code, exploring its meaning, potential causes, and troubleshooting steps. Understanding this code is crucial for maintaining your vehicle’s engine health and preventing potential damage.

Initially, a car owner reported experiencing this very issue on a 2013 Ford Fusion 1.6L. Despite the ECO warning and the appearance of the MIL, they noted the engine didn’t feel excessively hot to the touch. Further investigation revealed a low coolant level, prompting them to add more coolant. However, the warning persisted, even after replacing the Coolant Temperature Sensor (CTS).

The diagnostic codes retrieved in this case were:

• P018C – Fuel Pressure Sensor “B” Circuit Low
• P1299 – Cylinder head overtemperature protection active
• P2560 – Engine Coolant Level Low
• U0159 – Lost Communication with Parking Assist Control Module “A”

While the initial reaction might be to focus solely on the coolant temperature due to the “Engine Coolant Overtemp” message, the P1299 code specifically points to the cylinder head overheating. This is a critical distinction.

Ford Fusion Engine Bay and Diagnostic Codes Displaying P1299 Error

Understanding the P1299 Code and its Implications

The P1299 code is an OBDII (On-Board Diagnostics II) trouble code, and within the European EOBD (European On-Board Diagnostics) standard, it carries the same meaning. It indicates that the Powertrain Control Module (PCM) has detected a cylinder head overtemperature condition and has activated a protection strategy to prevent engine damage.

This “protection strategy” typically involves actions taken by the PCM to reduce engine temperature, such as:

• Fuel Cut-off: Reducing or cutting off fuel supply to cylinders to decrease combustion and heat generation.
• Ignition Timing Retard: Adjusting ignition timing to reduce combustion temperature.
• Limiting Engine Load/RPM: Restricting engine performance to reduce heat production.

The fact that the P1299 code is active even with the engine off, as reported in the initial case, suggests that the PCM might be retaining this code due to a persistent issue or a need for code clearing with a scan tool after the problem is resolved. Simply disconnecting the battery may not always clear this specific code.

Potential Causes of the P1299 Code

While the initial troubleshooting in the forum post focused on the Coolant Temperature Sensor (CTS), the P1299 code and the “Cylinder head overtemperature protection active” message suggest a broader range of potential problems. These can include:

1. Actual Engine Overheating: Despite the engine feeling cool to the touch, there could be localized overheating in the cylinder head area. This could be due to:

   • Low Coolant Level: As indicated by the P2560 code, low coolant can directly lead to overheating.
   • Coolant Circulation Issues: A faulty water pump, blocked coolant passages, or air pockets in the system can impede coolant flow and cause hot spots.
   • Thermostat Problems: A stuck closed thermostat prevents coolant from circulating through the radiator, leading to overheating.
   • Radiator Fan Malfunction: If the radiator fan isn’t operating correctly, especially at low speeds or when idling, it can reduce cooling efficiency.
   • Cylinder Head Gasket Leak: While often causing coolant in oil or exhaust, a head gasket leak can also lead to localized overheating.

2. Faulty Cylinder Head Temperature Sensor (CHT): Modern vehicles often use a dedicated Cylinder Head Temperature (CHT) sensor, separate from the CTS, to directly monitor cylinder head temperature. A malfunctioning CHT sensor could send false high-temperature readings to the PCM, triggering the P1299 code even if the engine isn’t actually overheating.

3. Wiring or PCM Issues: Less commonly, wiring problems in the CHT sensor circuit or a fault within the PCM itself could cause an erroneous P1299 code.

Troubleshooting Steps for the P1299 Code

Addressing the P1299 code requires a systematic approach:

1. Verify Coolant Level and System: Start by visually inspecting the coolant level and checking for any leaks. Examine the coolant condition – is it clean or contaminated? Consider pressure testing the cooling system to check for leaks.

2. Check for Coolant Circulation: With the engine running (if safe to do so without severe overheating), feel the upper and lower radiator hoses. They should both get hot, indicating coolant circulation through the radiator. If the upper hose is hot but the lower is cold, the thermostat might be stuck closed, or there could be a blockage.

3. Inspect Radiator Fan Operation: Ensure the radiator fan turns on when the engine reaches operating temperature or when the air conditioning is turned on.

4. Examine the CHT Sensor and Wiring: Locate the Cylinder Head Temperature (CHT) sensor. Consult a repair manual for your specific vehicle to find its location and testing procedures. Check the wiring and connectors for any damage or corrosion. Use a multimeter to test the sensor’s resistance and the wiring continuity, as outlined in a vehicle-specific repair manual.

5. Use a Scan Tool for Live Data: A scan tool is invaluable for diagnosing P1299. Monitor live data for both the Coolant Temperature Sensor (CTS) and Cylinder Head Temperature (CHT) sensor readings. Compare these readings to expected values. Check if the CHT reading is excessively high, even when the engine is not overheating.

6. Address Other Diagnostic Codes: The presence of other codes like P018C (Fuel Pressure Sensor) and P2560 (Coolant Level Low) should also be investigated as they might be related or contributing factors to the P1299 code. Low fuel pressure could potentially lead to lean conditions and increased engine temperature.

7. Professional Diagnosis: If you’ve performed these initial checks and the P1299 code persists, or if you are uncomfortable with these diagnostic steps, it’s best to seek professional diagnosis from a qualified mechanic. They have specialized tools and expertise to pinpoint the root cause of the problem accurately.

The EOBD/OBDII P1299 code is a serious indicator of potential engine overheating. Prompt and thorough diagnosis is essential to prevent engine damage and ensure the longevity of your vehicle. By understanding the potential causes and following a systematic troubleshooting process, you can effectively address this issue and get your vehicle back in optimal running condition.