OBD-II trouble code
P0218: Transmission Over Temperature Condition
The transmission fluid temperature has exceeded the safe threshold. The ECM/TCM logged an overheating event, which can accelerate fluid breakdown and internal wear if it keeps happening.
Quick facts
- System
- Powertrain
- Category
- Transmission
- Severity
- High severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $120 – $1,500
- DIY difficulty
- Intermediate DIY
What does P0218 mean?
P0218 sets when the transmission's fluid temperature rises above the safe limit the control module monitors. Automatic transmission fluid both lubricates and transfers hydraulic pressure, and it is very sensitive to heat — sustained high temperatures break the fluid down, reduce its ability to protect internal parts, and can lead to slipping, harsh shifts, and eventually serious damage. The code is the transmission's way of reporting that it got too hot, whether briefly under extreme load or repeatedly over time.
The most common causes are low or old/degraded transmission fluid, a restricted or failed transmission cooler (or a plugged cooler line), heavy loads such as towing or mountain driving, a stuck thermostat or cooling-system problem on shared-cooling designs, and internal transmission wear that generates excess heat. Because overheating is genuinely damaging, P0218 should be treated seriously even though the vehicle can usually still be driven: many vehicles will reduce power or limit shifting to protect the transmission until it cools. Start with fluid level and condition and cooler flow, since those are the cheapest and most frequent causes, before suspecting internal damage.
Common causes
- Low, old, or degraded transmission fluid
- Restricted, leaking, or failed transmission cooler or cooler lines
- Heavy towing, overloading, or prolonged high-load driving
- Cooling-system problem (stuck thermostat, low coolant) on shared-cooling designs
- Failed transmission fluid temperature sensor reading high
- Internal transmission wear or a slipping clutch generating excess heat
- Torque converter problem increasing heat load
Symptoms
- Check engine light and/or a transmission-temperature warning
- Reduced power or limited shifting (protection mode)
- Harsh, delayed, or slipping shifts
- Burnt-smelling or discolored transmission fluid
- Overheating during towing or climbing
Diagnostic steps
- 1.Scan and record all codes; note any transmission or cooling-system companions.
- 2.Check transmission fluid level and condition — low or burnt fluid is a leading cause.
- 3.Inspect the transmission cooler and lines for restriction, leaks, or damage, and confirm adequate flow.
- 4.On shared-cooling vehicles, verify engine coolant level and thermostat operation.
- 5.Compare the live transmission fluid temperature reading against actual temperature to rule out a bad sensor.
- 6.If fluid, cooler, and cooling system are good but temperatures still climb, inspect for internal wear or torque-converter issues.
Repair cost
$120 – $1,500
A fluid and filter service is often $120-$300 and resolves many cases caught early. Cooler or line repair varies. Sustained overheating that has already damaged the transmission internally is the expensive scenario, potentially well over $1,500. Address the heat source promptly to avoid internal damage.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with transmission fluid service preselected. Adjust labor rate and vehicle category to fit your situation.
Related repairs
DIY vs shop
This is an intermediate DIY job. It usually involves diagnostic steps, specialty parts, and some careful work in tight spaces. If you have the tools and a service manual or trustworthy video for your specific vehicle, it is achievable in a weekend. Otherwise, a competent independent shop will be faster.