Control module mounted in a hot location with poor cooling, or heat soak from nearby components such as the exhaust or engine; Internal fault in the control module's temperature sensing circuit; Power supply or earth fault to the module (poor connection, corroded terminals, low or unstable voltage) upsetting its internal readings; Water ingress, corrosion or damaged connector pins at the module; Faulty external component overloading the module, such as a shorted injector, coil or actuator driver; Outdated or faulty module software where the manufacturer has issued a known update for this fault.

P0669

Control Module Internal Temperature Sensor A Circuit High.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
6: AreaComputer and output circuits
69: FaultThe specific fault in that area

What it means

P0669 is the generic code for the internal temperature sensor 'A' inside a control module (usually the engine control unit, though which module it refers to depends on the vehicle) reporting a signal that is too high. The module monitors its own temperature with a sensor built into its circuit board. It sets this code when the sensor voltage or reading stays above the expected range, which can mean a genuine overheat condition or a fault in the module's own sensing circuit.

Symptoms

Engine warning light on
Reduced power or limp mode in some cases
Intermittent misfires, stalling or hard starting if the module is overheating
Other control module or communication fault codes stored alongside it
No noticeable symptoms other than the warning light

Possible causes

Control module mounted in a hot location with poor cooling, or heat soak from nearby components such as the exhaust or enginepossible
Internal fault in the control module's temperature sensing circuitlikely
Power supply or earth fault to the module (poor connection, corroded terminals, low or unstable voltage) upsetting its internal readingslikely
Water ingress, corrosion or damaged connector pins at the modulepossible
Faulty external component overloading the module, such as a shorted injector, coil or actuator driverpossible
Outdated or faulty module software where the manufacturer has issued a known update for this faultrare

How to diagnose

Read all stored codes and freeze frame data, noting engine temperature, battery voltage and whether the fault is current or historic
Check for other codes, especially module supply, communication or driver circuit faults, and address those first
Visually inspect the module, its mounting location and connectors for heat damage, moisture, corrosion or loose fixings
Check battery condition and charging voltage, then test the module's power feeds and earths for voltage drop under load
Check that nearby heat sources, shielding and any module cooling arrangements are intact (varies by model)
Clear the code and road test, watching live data for the module temperature value if available, and see whether the reading is implausible or rises with heat
Disconnect and test actuator and injector circuits that are driven by the module for shorts or excess current draw
Check the manufacturer's service information for software updates or known faults for this module and engine

How to fix

Repair or replace corroded or damaged connectors, terminals and wiring to the module
Correct power supply or earth faults and replace the battery or repair the charging system if voltage is unstable
Restore heat shielding or mounting position, and fix any water ingress source
Replace any shorted component that is overloading the module's output drivers
Update the module software only if the manufacturer lists it as the fix for this fault
Repair or replace the control module if its internal sensor is confirmed faulty, with coding or programming as required by the vehicle

Can I keep driving?

Medium severity

The car can usually be driven for a short time, but get it checked soon as an overheating or failing module could cause poor running, limp mode or a breakdown. If the engine runs roughly, stalls or loses power, stop driving and have it inspected.

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