Faulty cylinder head temperature sensor, typically an open or shorted thermistor element; Damaged or chafed wiring between the CHT sensor and the PCM, especially near hot exhaust components; Corroded or loose connector pins at the CHT sensor or PCM harness; High resistance in the sensor ground circuit, which pulls the signal below the self-test threshold; PCM internal fault on the CHT input circuit, though this is the least common cause; Coolant level low enough to expose the sensor tip, causing an artificially low reading during the self-test; Aftermarket sensor or pigtail with incorrect resistance characteristics installed during a previous repair

DTC codes / Ford codes / P1290

P1290 · FordCylinder Head Temperature Sensor Signal Less Than Self-Test Range

P1290 on a Ford means the powertrain control module (PCM) commanded a self-test of the cylinder head temperature (CHT) sensor circuit and the signal it read back was below the minimum value the test allows. The computer saw a voltage or temperature reading from the CHT sensor that was lower than any plausible reading for the engine at that moment, so it flagged the circuit as faulty.

SystemPowertrain

Code typeFord specific

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering (injector circuits)

Symptoms you may notice

Illuminated check engine light, often with no other noticeable symptoms
Rough idle or stumbling when the engine is cold, because the PCM is not receiving an accurate head temperature
Poor fuel economy or black smoke from the tailpipe if the PCM defaults to a rich fuel strategy
Cooling fan running constantly or not at all, since fan operation is tied to CHT readings on many Ford models
Hard starting or extended cranking when hot, if the PCM misjudges the engine temperature
Temperature gauge or dashboard message behaving erratically on vehicles that display CHT-derived data

Common causes, most likely first

Faulty cylinder head temperature sensor, typically an open or shorted thermistor element
Damaged or chafed wiring between the CHT sensor and the PCM, especially near hot exhaust components
Corroded or loose connector pins at the CHT sensor or PCM harness
High resistance in the sensor ground circuit, which pulls the signal below the self-test threshold
PCM internal fault on the CHT input circuit, though this is the least common cause
Coolant level low enough to expose the sensor tip, causing an artificially low reading during the self-test
Aftermarket sensor or pigtail with incorrect resistance characteristics installed during a previous repair

How to diagnose and fix it

Scan all modules and record freeze-frame data for P1290, then clear the code and verify whether it returns on a cold start
Inspect the CHT sensor connector and the harness run for chafing, heat damage, or pushed-out pins, and repair as needed
Measure the CHT sensor resistance with a multimeter and compare it to the Ford specification for the current engine temperature
Back-probe the sensor signal and ground wires at the PCM and check for excessive voltage drop on the ground side
Check coolant level and confirm the sensor is fully immersed, then top up and retest if low
Replace the CHT sensor with a Ford-specified part and clear the code, then run a cold-start self-test to confirm the repair
If the circuit tests good but the code persists, perform a PCM pin-fit and continuity test on the CHT input before condemning the PCM

Why a cold start matters for P1290

The self-test that sets P1290 runs under specific conditions, often after a cold soak, so a warm engine may pass the test and hide the fault until the next morning.
A low coolant level can expose the CHT sensor tip and produce a reading below the self-test range even when the sensor and wiring are perfectly good.
Technicians sometimes replace the CHT sensor when the real problem is a corroded ground splice shared with other sensors, so always check ground integrity first.
On some Ford engines the CHT sensor is a two-wire thermistor and on others it is integrated into a coolant temperature sensor assembly, so confirm the exact configuration before ordering parts.
P1290 does not always mean the sensor has failed; a pinched harness behind the intake or near the thermostat housing can short the signal to ground intermittently.

Can I keep driving with P1290?

You can usually drive the vehicle short distances to a repair shop, but avoid heavy loads, long trips, and towing until the fault is repaired because the PCM may be running a default fuel and fan strategy. If the engine overheats or the cooling fan stops working, pull over and stop driving.

Tools that help

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Guidance is general and written for Ford vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.