Damaged wiring or short to voltage on the coolant heater B control circuit; Corroded, loose or contaminated connector at the heater or control unit; Faulty heater relay or switching module for heater B (where fitted); Internal fault in the coolant heater element or its integrated electronics; Open circuit or poor earth causing the control line to read high; Fault in the engine control unit output driver or outdated software where a known issue is documented.

P01EE

Engine Coolant Heater B Control Circuit High.

Generic
Powertrain
Generic code
Low severity

How this code is built

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

What it means

P01EE means the engine control unit has detected a high voltage or high signal state on the control circuit for engine coolant heater B. This is usually a fault in the circuit itself, such as a short to voltage, an open circuit that lets the line float high, or a driver fault, rather than a failure to heat. The exact location and design of heater B, and how the unit monitors it, vary by model and engine, so check manufacturer data.

Symptoms

Engine warning light on
Slow cabin warm-up in cold weather
Engine takes longer to reach operating temperature
Poor heater output on cold starts
Higher fuel consumption on short cold journeys
Possible other heater-related codes stored

Possible causes

Damaged wiring or short to voltage on the coolant heater B control circuitlikely
Corroded, loose or contaminated connector at the heater or control unitlikely
Faulty heater relay or switching module for heater B (where fitted)possible
Internal fault in the coolant heater element or its integrated electronicspossible
Open circuit or poor earth causing the control line to read highpossible
Fault in the engine control unit output driver or outdated software where a known issue is documentedrare

How to diagnose

Read all stored and pending codes and note any related heater, coolant temperature or battery voltage codes
Review freeze frame data, including coolant and ambient temperature and battery voltage when the code set
Visually inspect the heater B wiring, connector and any relay or fuse for chafing, corrosion, water ingress or heat damage
Check the supply fuse and relay for heater B against the wiring diagram for that model
Use a scan tool to command the heater on and off, if supported, and watch whether the circuit state changes
With the connector unplugged, test the control wire for short to voltage, open circuit and earth integrity against the wiring diagram
Measure the heater element resistance and compare with the manufacturer specification
Check for applicable software updates or technical bulletins for the model before suspecting the control unit

How to fix

Repair or replace damaged wiring and fix any short to voltage on the control circuit
Clean, repair or replace corroded or damaged connectors and terminals
Replace a faulty relay or switching module for heater B
Replace the coolant heater if its element or integrated electronics are faulty
Restore a poor earth or open circuit connection found during testing
Replace or reprogram the control unit only after the wiring and heater are proven good, or if a calibration fix is documented

Can I keep driving?

Low severity

The car can usually be driven as the fault mainly affects warm-up and cabin heat. Book it in soon, and keep an eye on the temperature gauge and any other warning lights.

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