If your engine cranks longer than normal or your temperature gauge acts strangely, the cylinder head temperature sensor is one of the first parts you should check. This sensor is a thermistor threaded into the cylinder head that reads the metal temperature directly and sends that signal to the powertrain control module (PCM), which uses that signal to set fuel delivery, spark timing, and cooling fan speed.
In This Article
Explore Our Categories
How a Cylinder Head Temperature Sensor Works
Inside the housing sits a negative temperature coefficient (NTC) thermistor. As cylinder head temperature rises, resistance drops, and your PCM reads that change as a temperature value.
Where Is the Sensor Located?
On most Ford applications, the engine cylinder head temperature sensor threads into a port on the left cylinder head, usually below the intake manifold or near the rear of the head.
6 Symptoms of a Failing Sensor
- Check engine light. The most common first warning.
- Hard starting when warm. Incorrect temperature readings affect fuel delivery.
- Cooling fans running at full speed. The PCM defaults to protection mode.
- Dead or erratic temperature gauge.
- Rough idle and lost power.
- Overheat warnings or failsafe mode.
Diagnostic Trouble Codes to Look For
| Code | Meaning |
|---|---|
| P1285 | Cylinder head over temperature condition |
| P1288 | Sensor circuit out of self-test range |
| P1289 | Cyover-temperature sensor signal greater than self-test range |
| P1290 | Cylinder head temperature sensor signal less than self-test range |
| P1299 | Head over temperature protection active |
CHT Sensor vs. Coolant Temperature Sensor
The engine coolant temperature (ECT) sensor reads coolant temperature, while the cylinder head temperature sensor reads the actual temperature of the head casting.
How to Test It
- Scan for codes and record freeze frame data.
- Inspect the connector and wiring for damage.
- Compare live freeze-frame readings.
- Measure sensor resistance against factory specifications.
- Check reference voltage and ground circuits.
Replacement Cost and Tips
An engine cylinder head temperature sensor usually costs $20 to $90. Labor can range from $75 to $300 depending on accessibility. A V8 requiring intake manifold removal can increase the total repair cost.
Why Do Overheating Codes Come Back After Replacing the Sensor?
Repeated overheating codes after replacing the sensor may indicate deeper issues, including a warped cylinder head, failed head gasket, or restricted cooling passages.
Frequently Asked Questions
Can I drive with a bad cylinder head temperature sensor?
You can, but we do not recommend it. A faulty reading prevents your PCM from properly protecting the engine.
How long does replacement take?
You can usually expect replacement to take about 30 minutes on an accessible four-cylinder engine. If you have a V8 where the intake manifold needs to be removed first, plan for around two to three hours to complete the job.
Will a bad cylinder head temp sensor stop the engine from starting?
Yes. Incorrect temperature readings can cause the PCM to deliver the wrong fuel amount, leading to extended cranking or a no-start condition.
Does high voltage on a CHT sensor mean the engine is hot?
No. Since the CHT sensor is an NTC thermistor, voltage drops as temperature increases. High voltage usually indicates the PCM is seeing a cold condition.
Final Thoughts
A cylinder head temperature that sensor is a small component that protects one of your engine’s most expensive parts. Always diagnose the wiring, check sensor resistance, and verify readings before replacing components.
That is where we can help. Allied Motor Parts stocks remanufactured, new, and performance cylinder heads, head kits, and gasket sets backed by a 1-year warranty.
