Code
P0218
SEAT
P — Powertrain
Temp light - transaxle hot
AI status
Completed
Completed
100%
Causes
- Low transmission fluid level
- Contaminated, degraded or burnt transmission fluid
- Faulty transmission temperature sensor or switch
- Open/short/corroded wiring or poor connector at temperature sensor
- Blocked or damaged transmission fluid cooler or cooler lines
- Radiator/auxiliary cooler or fan not operating properly
Symptoms
- Transmission/transaxle temperature warning light illuminated
- Transmission may enter limp mode or reduced performance
- Harsh shifting, slipping or delayed gear engagement
- Burning smell from transmission area
- Dark, burnt-smelling transmission fluid or metal particles in fluid
- Erratic temperature readings on a scan tool or gauge
What to check
- Confirm DTC and read freeze-frame data with a diagnostic scanner (operating temp, vehicle speed, load)
- Retrieve live transmission fluid temperature from scan tool and compare to ambient and expected values
- Visually inspect transmission fluid level and condition (check for dark color, burnt smell)
- Inspect temperature sensor connector and wiring for corrosion, damage, pin push-out, or water ingress
- Check transmission cooler, cooler lines and radiator/condenser for blockage, kinks, leaks or collapsed hoses
- Verify cooling fan(s) and fan control operation, and A/C condenser airflow
Signal parameters
- Typical transaxle fluid operating temp: approximately 70–100°C (158–212°F) under normal driving; prolonged values above ~120–140°C (248–284°F) indicate overheating (manufacturer-specific)
- Transmission temperature sensor is commonly a thermistor (NTC) or switch with a 0–5 V signal to the TCM/ECM — voltage/resistance varies with temp (resistance usually decreases as temperature rises for NTC sensors)
- Over-temperature DTCs may be set when the sensor report exceeds the manufacturer high-temperature threshold or when sensor circuit voltage is out of range
Diagnostic algorithm
- Confirm P0218 is current — read freeze-frame and related codes; note vehicle conditions when stored (speed, load, ambient temp).
- With engine warmed, read transmission fluid temperature with a scan tool and compare to ambient; if possible measure fluid temperature directly with probe at fluid pan or cooler line and compare to scan tool reading.
- Inspect fluid level and condition; if low, correct level and inspect for leaks. If fluid is burnt or contaminated, plan for fluid change and flush of cooler lines.
- Inspect transmission temperature sensor/switch: check connector for corrosion, bent pins or poor fit; back-probe sensor and check voltage/resistance against manufacturer data. Replace sensor if out of spec.
- Inspect cooler system: check radiator/auxiliary cooler, cooler lines, and transmission oil cooler for restriction or external blockage; ensure hoses are not collapsed.
- Verify cooling fan(s), fan clutch or electric fan operation and A/C condenser cleanliness to ensure adequate airflow.
- If wiring fault suspected, perform continuity and resistance checks from sensor connector to TCM/ECM and check for shorts to power/ground. Repair wiring as needed.
- After repairs, clear codes and perform road test under similar load conditions while monitoring transmission temperature; confirm code does not return.
- If overheating persists with good sensor readings and cooling system, investigate internal transmission issues (clutch pack wear, valve body blockage, failing torque converter) and consult transmission specialist.
Likely causes
- Low/old/contaminated transaxle fluid reducing cooling capacity
- Faulty temperature sensor/switch or connector corrosion
- Restricted fluid flow through cooler (clogged cooler, collapsed hose, external debris)
- Cooling fan or condenser airflow restriction (blocked fins, failed fan)
Fault status
Status
Transmission temperature warning — transaxle reported overheated or transmission temperature sensor circuit indicates high temperature.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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