Engine Temperature Gauge Circuit Malfunction
What does B1404 mean?
The B1404 code means the vehicle's onboard diagnostic system has detected: Engine Temperature Gauge Circuit Malfunction. This is a moderate severity code.
Common Symptoms
- Temperature gauge not reading
- Gauge stuck on cold even after engine warms up
- Temperature gauge reads maximum immediately
- Erratic temperature gauge fluctuations
- No overheat warning despite hot engine
Probable Causes (Ranked by Likelihood)
- Failed engine coolant temperature sensor for gauge Very High
- Corroded temperature sensor connector High
- Faulty gauge stepper motor in instrument cluster Moderate
- Damaged wiring from sensor to cluster or PCM Moderate
- Instrument cluster internal fault Low
Step-by-Step Diagnostic Procedure
-
Check coolant temperature reading on scan tool
-
Compare scan tool temperature to gauge reading
-
Test coolant temperature sensor resistance
-
Inspect sensor connector for corrosion
-
Perform instrument cluster self-test
Frequently Asked Questions
Is this the same sensor used by the engine computer?
Some vehicles use one sensor for both the gauge and PCM, while others have two separate sensors. Check your vehicle's wiring diagram to determine which applies.
Can I overheat without knowing if the gauge is broken?
Yes. Without a working temperature gauge or warning light, you will not know the engine is overheating until significant damage occurs. Monitor the scan tool temperature reading as a precaution.
How do I test the coolant temperature sensor?
Measure the sensor's resistance with a multimeter and compare it to the specification for the current coolant temperature. Resistance should change as temperature changes.