P050C
Cold Start Engine Coolant Temperature Performance.
- Generic
- Powertrain
- Generic code
- Low severity
How this code is built
- P
- SystemPowertrain
- 0
- Defined bySAE, the same on every car
- 5
- AreaVehicle speed, idle control and auxiliary inputs
- 0C
- FaultThe specific fault in that area
What it means
P050C is the generic code for a cold start engine coolant temperature performance fault. The control unit has compared the coolant temperature reading after a cold start with what it expects, such as the intake air temperature, or how quickly the engine should warm, and the values did not agree sensibly. The exact test and thresholds vary by manufacturer and engine, so check the model-specific procedure.
Symptoms
- Check engine light on
- Hard or extended cranking when starting from cold
- Rough or unstable idle until warm
- Poor fuel economy or a rich-smelling exhaust on cold starts
- Cooling fans running at odd times or temperature gauge reading incorrectly
- Cabin heater slow to warm up or not warming properly
Possible causes
- Faulty engine coolant temperature sensor reading inaccurately or slowlylikely
- Damaged wiring, corrosion or poor connection at the coolant temperature sensor connectorlikely
- Thermostat stuck open, so the engine warms too slowlylikely
- Low coolant level or air trapped in the cooling system giving false readingspossible
- Faulty intake air temperature sensor or other sensor used for the cold start comparisonpossible
- Engine block heater or coolant heater affecting the cold start values (where fitted)rare
- Fault within the control unit or an outdated calibration, where the manufacturer has identified thisrare
How to diagnose
- Read the stored and pending codes and the freeze frame data, noting coolant and intake air temperatures at the time the code set
- Check for other related codes, such as coolant temperature circuit or thermostat codes, and deal with those first
- Check the coolant level and condition when the engine is cold, and look for leaks
- Inspect the coolant temperature sensor wiring and connector for damage, corrosion, moisture or a loose fit
- With the engine fully cold (left overnight), compare the live coolant temperature with the intake air temperature and a known ambient temperature; they should be close
- Watch the live coolant temperature as the engine warms and look for jumps, lag or a reading that stalls
- Check the sensor's resistance against the manufacturer's specification at a known temperature
- Check the thermostat operation and that the engine reaches normal operating temperature in a reasonable time
How to fix
- Replace the engine coolant temperature sensor if it reads inaccurately or fails the resistance check
- Repair or replace damaged wiring or connectors in the sensor circuit
- Replace a thermostat that is stuck open or opens too early
- Top up or refill the coolant and bleed the system to remove trapped air, fixing any leak found
- Replace a faulty intake air temperature sensor if it is the cause of the comparison fault
- Apply a manufacturer calibration update only if one is published for this fault
Can I keep driving?
Low severity
The car can normally be driven while you book it in, but a wrong coolant reading can cause poor running and economy. Keep an eye on the temperature gauge and stop if the engine overheats.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.