P01E4: Engine Coolant Temperature Sensor 3 Circuit Range/Performance

Coolant temperature sensor 3 is a third NTC coolant sensor on engines with thermal management or split cooling circuits; its position is defined by the manufacturer – on Jaguar Land Rover's 2018–2019 Ingenium petrol engines it sits in the engine block water jacket, on Audi's 3.0 TFSI V6 it is part of the thermal management. As with every NTC sensor, a low signal voltage means hot and a high one cold. CARB requires such additional sensors to be monitored from model year 2019 onwards. P01E4 means the signal is electrically valid but implausible. Audi documents it on 2017–2021 3.0 TFSI V6 models together with cooling system, cylinder head temperature and 'engine temperature too low' codes: the cause was a thermostat that did not close fully, and Audi states that replacing the sensor does not fix it.

Symptoms

• Check engine light on
• Engine warms up slowly, heater output weak
• Often together with cooling system codes

Most likely causes

• Thermostat not closing fully
• Sensor 3 drifting
• Low coolant or air at the sensor
• Contact resistance at the connector

What to check, in order

Start with the simplest. You can tick off each step.

1. With the engine cold, check the coolant level; never do this when the system is hot
2. Compare the reading with other engine data while varying the engine speed.
3. Check the actual temperature in live data
4. Make sure the fan comes on when it should
5. Check the thermostat and connector
6. Measure the sensor and replace it if its readings do not make sense

Good to know

• Repair difficulty: medium
• It affects emissions.

What each character of P01E4 means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• 1: Air and fuel
• E4: Specific fault in that system

Frequently asked questions

Can I keep driving with code P01E4?

Watch the temperature gauge. If it climbs or a warning appears, stop the car in a safe place and turn off the engine: overheating can cause serious damage.

What causes code P01E4?

The most common causes are: thermostat not closing fully; sensor 3 drifting; low coolant or air at the sensor.

Related codes

• P01E3Engine Coolant Temperature Sensor 3 Circuit
• P01E5Engine Coolant Temperature Sensor 3 Circuit Low
• P01E6Engine Coolant Temperature Sensor 3 Circuit High
• P0128Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)
• P017BCylinder Head Temperature Sensor A Range/Performance
• P2181Cooling System Performance

Sources

• law.cornell.edu: 13 CCR 1968.2
• static.nhtsa.gov: MC 10208895 0001
• static.nhtsa.gov: MC 10172596 0001

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.