P0218: Transmission Fluid Temp Sensor (TFT) Over Temperature

What Does Code P0218 Mean?

When an OBD-II vehicle has a code P0218 stored in the computer, it means that the transmission fluid temperature that is being measured by a sensor and read by the powertrain control module (PCM) has exceeded the temperature limit- normally about 290 degrees for a calculated period of time.

How Is Trans. Fluid Heated and Cooled

The oil pan is where the transmission fluid is stored. Normal capacity is about 4-5 quarts. This is not the fluid capacity of the entire transmission, just what is in the pan. Fluid is drawn through the filter and the valve body assembly before it goes through the transmission case passages on it's way to the pump.

Trans. fluid is pressurized in the oil pump where it is then directed to the pressure regulator valve. It then supplies fluid to the transmission hydraulic circuits including all of the internal components such as pistons, valves, clutches and various other components.

The now heated fluid flows into the transmission cooler lines through the torque converter clutch (TCC) apply valve and to the radiator which has a cooler interanl and seperate from the antifreezze, or to an external cooler. The cooled fluid then returns to the transmission to lubricate and remove heat again in an endless cycle.

Code P0218 Symptoms

• Low fluid level in the transaxle or transmission
• Fluid leaking from an internal torque converter seal, pan or cooler
• No gear engagement, slipping
• Limp home mode activated by the PCM

Common Causes of P0218

• Faulty transmission fluid temperature (TFT) sensor
• Damaged or missing front air dam or spoiler
• Broken cooling fan or fan clutch
• Low transmission fluid
• Fluid leak from torque converter seal, pan, cooler, etc.
• Debris or other restrictions in transmission cooler
• Transmission lines or cooler restricted
• Towing overloaded trailer leading to overheating

How to Diagnose P0218?

This code will not cause a check a check engine light, so a symptom above would be the only indicator a code is store. A mechanic would first scan the computer and find this code. To diagnose, a mechanic wwill usually start by checking the condition and level of the transmission fluid. There may be some damage to the transmission parts if the fluid smells burnt or is low.

The technician will look for leaks at any of the transmission external gaskets or the cooling system. Before any further diagnosis can take place, any leaks will need to be repaired and the transmission fluid must be at the proper level. Low fluid level will quickly cause it to become overheated as well as internal parts.

What Will Fix Code P0218?

This code is usually set as a result of serious internal problems- just like an overheating engine. A bad sensor can cause the code but that is not as likely. First, you may need to replace any gaskets, cooler lines, hoses, or a radiator to fix a leak. If the fluid is not low but is burnt then either a component such as a clutch pack is slipping, a valve is sticking or the cooler is plugged not alowwing proper heat transfer. Cleaning the outside of the radiator or cooler and flushing the inside can fix code P0218.