P0115
Engine Coolant Temperature Circuit
- Severity
- Medium
- Driving
- Drivable — book it in
A fault in the engine coolant temperature sensor circuit. This reading matters more than most people expect: the module uses it to decide how much extra fuel to add when cold, when to enable closed-loop fuelling, and when to run the cooling fans. A wrong reading has knock-on effects across all of those.
Possible causes
- CommonFailed coolant temperature sensor
- CommonDamaged wiring or connector at the sensor
- PossibleLow coolant level leaving the sensor out of the coolant
- PossibleCorrosion in the connector
What you might notice
- Check engine light on
- Worse fuel economy
- Cooling fans running constantly or not at all
- Harder starting
- Temperature gauge reading implausibly
What to check, in order
- Check the coolant level first - a sensor sitting in air rather than coolant reads wrongly through no fault of its own.
- Compare the coolant temperature reading on the live data screen against the gauge and against intake air temperature on a cold engine. On a cold car all should read close to ambient.
- Inspect the connector for corrosion and the wiring for chafing.
- Replace the sensor once wiring and coolant level are eliminated.
Read this code from your own car
Plug an ELM327 adapter into the OBD-II port under the dashboard. Pin16 reads every stored, pending and permanent code, explains each one like this page does — offline, with no account — and shows what the car recorded when the fault was set.
Where this code sits
P00xxP01xxP02xxP03xxP04xxP05xxP06xxP07xxP08xxP09xxP0AxxP0BxxP0CxxP0DxxP0ExxP0FxxP10xxP11xxP12xxP13xxP14xxP15xxP16xxP17xxP18xxP19xxP1AxxP1BxxP1CxxP1DxxP1ExxP1FxxP20xxP21xxP22xxP23xxP24xxP25xxP26xxP27xxP28xxP29xxP2AxxP2BxxP2CxxP2DxxP2ExxP2FxxP30xxP31xxP32xxP33xxP34xxP35xxP36xxP37xxP38xxP39xxP3AxxP3BxxP3CxxP3DxxP3ExxP3Fxx
Fuel and air metering
P0100P0101P0102P0103P0104P0105P0106P0107P0108P0109P0110P0111P0112P0113P0114P0115P0116P0117P0118P0119P0120P0121P0122P0123P0124P0125P0126P0127P0128P0129P0130P0131P0132P0133P0134P0135P0136P0137P0138P0139P0140P0141P0142P0143P0144P0145P0146P0147P0148P0149P0150P0151P0152P0153P0154P0155P0156P0157P0158P0159P0160P0161P0162P0163P0164P0165P0166P0167P0168P0169P0170P0171P0172P0173P0174P0175P0176P0177P0178P0179P0180P0181P0182P0183P0184P0185P0186P0187P0188P0189P0190P0191P0192P0193P0194P0195P0196P0197P0198P0199