P0218 Code: Transmission Over Temperature — Meaning & Fix

Sun West Transmissions — Glendale, AZ. Free estimates, honest diagnosis and a 3-year / 40,000-mile warranty on qualifying rebuilds and replacements.

What Does P0218 Mean?

P0218 is the code for “Transmission Fluid Over Temperature Condition.” Your transmission computer monitors fluid temperature through a sensor, and when it records temperatures above a calibrated limit for a period of time, it sets P0218. Some vehicles also display a message such as “Transmission Hot” or “Transmission Overheating.”

This is one of the most important transmission codes for Phoenix-area drivers. Heat is the number one enemy of automatic transmission fluid, seals and clutches, and the West Valley gives transmissions plenty of it: summer air temperatures well above 100 degrees, hot pavement, stop-and-go traffic and lots of trucks pulling trailers and boats. Read more in how Arizona heat affects your transmission.

What To Do Right Away

1. When it is safe, pull over or ease off. Reduce load and speed.
2. Shift into Park and let the engine idle for a few minutes so the pump keeps circulating fluid through the cooler. Do not shut the engine off unless the engine itself is overheating or the manufacturer instructs otherwise.
3. If towing, consider whether you can continue at lower speed or need to stop and wait for cooler temperatures.
4. Watch the engine temperature gauge too. A cooling system failure can overheat both engine and transmission.

Never open a hot radiator cap or touch transmission lines, the pan or the cooler after driving. Fluid and components can cause serious burns.

Common Causes of Transmission Overheating

Heavy Loads and Towing

Towing a camper up I-17 toward Sunset Point, hauling a trailer on the Carefree Highway or pulling a boat to Lake Pleasant on a summer afternoon pushes fluid temperatures up fast. Running in a gear that does not allow converter lockup adds even more heat. See towing and your transmission.

Low or Degraded Fluid

Low fluid means less fluid to carry heat away. Old fluid oxidizes and loses its ability to protect parts. Burnt fluid both causes and indicates overheating.

Restricted Cooling

Transmission coolers in the radiator or in front of it can become clogged externally with dirt and bugs, or internally with debris. Kinked cooler lines, a failing radiator, a weak cooling fan or a stuck thermostat bypass valve can all reduce cooling.

Torque Converter Slip

A converter clutch that will not lock, or slips when locked, generates large amounts of heat. Codes such as P0741 often appear alongside P0218.

Internal Slipping

Worn clutches or low line pressure make clutches slip, which turns engine power into heat. A slipping transmission and an overheating transmission are often the same transmission.

Sensor Problems

Occasionally the temperature reading is wrong. A faulty sensor can set over-temperature codes when the fluid is actually normal. See P0711.

What You Can Check

• Fluid level and smell, using the correct procedure for your vehicle
• The front of the radiator and any auxiliary cooler for debris
• Coolant level when the engine is cold
• Whether the cooling fan runs when the A/C is on or the engine is hot

How Sun West Diagnoses P0218

We review freeze-frame data to see the temperature, speed, gear and load when the code set. Then we inspect fluid level and condition, the cooler, cooler lines and radiator, and check cooling fan operation. On a road test we monitor fluid temperature, converter slip and gear ratios to spot slipping. If the fluid is burnt, we inspect the pan for friction material and metal to judge internal condition.

The goal is to find and fix the source of the heat, not just clear the code. Our transmission diagnostic testing covers this process.

Is It Safe to Keep Driving?

Driving with an overheating transmission can destroy it quickly. Seals harden, clutches glaze and fluid breaks down. Stop driving if the warning stays on after cooling down, if the transmission slips or smells burnt, or if the engine also overheats.

Repair Options

Depending on the cause, repairs may include a fluid service, cooler flush or replacement, radiator replacement, an auxiliary transmission cooler installation, torque converter replacement, or a rebuild if internal damage has occurred. Cost depends on the vehicle and findings, so call for a free quote. Qualifying rebuilds and replacements include our 3-year / 40,000-mile warranty.

P0218 Code FAQ

Can a transmission recover after overheating once?

Sometimes, if it was brief and the fluid is changed promptly. Repeated overheating causes lasting damage.

Will an auxiliary cooler stop P0218?

It helps a lot for towing and summer driving, but it will not fix internal slipping. See our auxiliary cooling system page.

Should I change my fluid after an overheat?

Yes, overheated fluid loses its protective properties. Have it inspected and serviced.