OBD-II Diagnostic Trouble Code
P0218 — Transmission Over Temperature Condition
P0218 means the transmission fluid temperature exceeded the over-temperature threshold. It is a condition code indicating actual overheating of the transmission, usually an automatic or automated transmission, rather than a sensor circuit fault. Confirm the reading before replacing parts.
Severity 4/5
Truck-relevant
Stop within 50 mi
Severity
Stop within 50 mi
Transmission Over Temperature Condition
Code
P0218
Category
Powertrain
Subsystem
Transmission
Truck-relevant
Yes
What this means for truckers
Stop within ~50 miles on a Cummins X15, Detroit DD15, PACCAR MX-13. Driving longer risks damaging adjacent components (turbo housing, head gasket, aftertreatment) and turning a $300 fix into a $3,000 fix.
Before you replace parts — try this first
P0218 on the Transmission system is most often low or degraded transmission fluid — not a dead part. On commercial diesels especially, work these in order before spending money on parts:
- Confirm the symptoms. Match what your truck is doing to the Symptoms section below. If the code is set but the symptoms are not there, clear the code and re-test after a drive cycle — it may not return.
- Clean and dry the sensor connector. Water, road salt, or oil seeping into a connector is the #1 fake sensor failure. Disconnect, look for green corrosion or moisture, spray with electrical contact cleaner, dry, reseat. Many faults clear here for $0.
- Inspect the wiring harness. Trace the wire from the sensor toward the ECM — look for chafing against the engine block, melted insulation near the turbo or exhaust, or pinch points where a clamp has rubbed through.
- Test the sensor before swapping it. Most Common Causes (below) list the expected voltage or resistance range — a $20 multimeter saves a $300 sensor swap that does not fix the problem.
- Only then, replace the part. Use the OEM or a tier-1 aftermarket. Cheap sensors throw the same code in two weeks.
Symptoms
Transmission temperature warning, harsh or delayed shifts, the transmission may hold gears or enter limp mode, and fluid may smell burnt. Overheating often happens when hauling heavy, idling long in gear or on long grades.
Common causes
- CommonLow or degraded transmission fluid ($150–$500)
- CommonRestricted or blocked transmission cooler or cooler lines ($200–$1000)
- CommonHeavy load or severe duty operation beyond cooling capacity ($0–$300)
- OccasionalInternal slipping clutches or torque converter problem ($1500–$7000)
- RareFaulty transmission temperature sensor ($150–$500)
How to fix
Check fluid level and condition and change fluid and filters if degraded
When to use: First step
Inspect and flow-test the cooler and lines, clean or replace as needed
When to use: When fluid is good but temperature climbs
Verify temperature with an infrared thermometer against the scan tool value
When to use: To rule out a false sensor reading
Perform stall and slip tests and check for internal faults
When to use: When fluid is burnt or slipping codes are present
Affects most
No specific vehicle pattern found in our complaint database. This code can appear on any vehicle that supports OBD-II diagnostics.
Related
- → Browse all DTC trouble codes
- → Decode a VIN to check codes for your truck
- → Owner-operator maintenance guides
- → P0200 — Injector Circuit Malfunction
- → P0201 — Injector Circuit Malfunction - Cylinder 1
- → P0202 — Injector Circuit Malfunction - Cylinder 2
- → P0203 — Injector Circuit Malfunction - Cylinder 3
- → P0204 — Injector Circuit Malfunction - Cylinder 4
Frequently Asked Questions
Can I drive with code P0218?
Drive with caution. P0218 is severity 4 — stop within ~50 miles. Most commercial diesel codes at this severity (turbo, fuel rail, transmission solenoid) can damage adjacent expensive components if left unrepaired. Get to a service location before highway-speed loads.
How much does it cost to fix P0218 on a commercial truck?
Total repair cost ranges varies depending on the root cause. The cheapest fix is usually the first one listed below — Low or degraded transmission fluid — which is also the most common. On commercial trucks the cost is usually higher than passenger vehicles due to part availability and shop labor rates ($120–185/hour at most truck shops, vs $90–130 at general auto shops). DIY-capable fixes (sensors, hoses, filters) are at the low end; major component replacements (turbo actuator, high-pressure fuel pump, transmission solenoid pack) are at the high end. Always diagnose with a scan tool BEFORE replacing parts — guessing wrong on a $1,500 turbo actuator when the actual issue was a $30 boost hose is a common expensive mistake.
Will P0218 fail a DOT inspection?
P0218 typically doesn't fail an inspection on its own. Inspectors focus on safety items (brakes, steering, tires, lights, HOS). Transmission codes only become an issue if the truck has shifting problems severe enough to qualify as 'mechanical fitness' OOS. Fix to prevent escalation.
What's the difference between P0218 and related codes?
P0218 is closely related to: P0200 (Injector Circuit Malfunction), P0201 (Injector Circuit Malfunction - Cylinder 1), P0202 (Injector Circuit Malfunction - Cylinder 2), P0203 (Injector Circuit Malfunction - Cylinder 3). These codes share the same subsystem (transmission) and often appear together. If you see this code, scan for the full code list — fixing the root cause usually clears multiple companion codes at once. If only P0218 is set without the companions, the issue is more isolated.
How do I prevent P0218 from coming back after a repair?
For P0218 (Transmission Over Temperature Condition), prevention centers on the transmission system. Service transmission fluid at the OEM interval (typically 150K–250K miles for HD autos). Don't skip the magnet/strainer inspection. After repair, perform an adaptive shift relearn with a scan tool (or drive 40+ miles for adaptive ECMs to relearn naturally).