Faulty or drifting coolant temperature sensor 3; Corroded, loose or damaged connector terminals at the sensor; Damaged wiring, with chafing, high resistance or a poor earth or reference; Low coolant level or air trapped in the cooling system giving false readings; Thermostat or cooling flow fault causing a genuine temperature mismatch; Engine control unit fault or outdated software, only where the manufacturer lists it as a known cause.

P01E4

Engine Coolant Temperature Sensor 3 Circuit Range/Performance.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
1: AreaFuel and air metering
E4: FaultThe specific fault in that area

What it means

P01E4 is a generic code meaning the engine control unit has found that the signal from engine coolant temperature sensor 3 is out of range or does not make sense when compared with expected values or other temperature inputs. The sensor circuit is not fully open or shorted, but the reading is implausible, stuck, slow to respond or drifting. Which part of the cooling system sensor 3 monitors depends on the vehicle and engine.

Symptoms

Engine warning light on
Temperature gauge reading incorrectly or erratically
Cooling fan running constantly or at the wrong times
Poor fuel economy or rough running
Hard starting when hot or cold
Heater output not matching engine temperature

Possible causes

Faulty or drifting coolant temperature sensor 3likely
Corroded, loose or damaged connector terminals at the sensorlikely
Damaged wiring, with chafing, high resistance or a poor earth or referencepossible
Low coolant level or air trapped in the cooling system giving false readingspossible
Thermostat or cooling flow fault causing a genuine temperature mismatchpossible
Engine control unit fault or outdated software, only where the manufacturer lists it as a known causerare

How to diagnose

Read all stored and pending codes and the freeze frame data, noting coolant temperature and engine run time when the code set.
Check the coolant level when the engine is cold and look for leaks, signs of air in the system or poor coolant condition.
Find where sensor 3 is fitted on this engine using the manufacturer's data, then inspect its connector and wiring for damage, corrosion, moisture or chafing.
With live data, compare sensor 3 with the other coolant temperature readings and the intake air temperature on a fully cold engine; they should be close.
Watch the sensor 3 reading as the engine warms up and check it rises smoothly and plausibly, without jumps or freezing.
Measure the sensor resistance and the circuit voltage, reference and earth against the manufacturer's specification.
Check the thermostat and cooling flow, for example with an independent temperature measurement of the housing or hose.
Check for relevant software updates or technical bulletins for this model once the hardware checks are complete.

How to fix

Replace coolant temperature sensor 3 if its readings or resistance are out of specification.
Clean, repair or replace the damaged connector terminals and fix any wiring faults found.
Top up and correctly bleed the cooling system with the correct coolant mix, and repair any leaks.
Replace a faulty thermostat or repair the cooling flow problem that is causing a real temperature difference.
Update the control unit software only if the manufacturer identifies an outdated calibration as a cause for this fault.

Can I keep driving?

Medium severity

The car can usually be driven for a short time, but book it in soon because poor temperature data can cause incorrect fuelling and cooling fan control. If the temperature gauge reads high or the engine overheats, stop driving and have it checked.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.