Engine Hot Lamp Control Circuit Malfunction (Chevrolet)
What does P1673 mean?
The P1673 code means the vehicle's onboard diagnostic system has detected: Engine Hot Lamp Control Circuit Malfunction (Chevrolet). This is a critical severity code.
Common Symptoms
- Engine overheating warning light on
- Temperature gauge reading high
- Check Engine Light on
- Overheating warning not displaying when engine is hot
- Steam from engine compartment
Probable Causes (Ranked by Likelihood)
- Faulty coolant temperature sensor for warning circuit Very High
- Actual engine overheating condition High
- Open or shorted wiring in hot lamp circuit Moderate
- Instrument cluster or PCM lamp driver failure Low
Step-by-Step Diagnostic Procedure
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Immediately check the coolant temperature gauge and scan tool reading. If the engine is actually overheating, stop and address the cooling system.
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If the engine is not overheating, test the coolant temperature sensor resistance at various temperatures.
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Inspect wiring between the temperature sensor and the instrument cluster or PCM.
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Check the warning lamp bulb or LED in the instrument cluster during the key-on bulb check.
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Verify the cooling system is functioning: check coolant level, thermostat, water pump, and radiator fan.
Frequently Asked Questions
Is my engine actually overheating?
You must verify immediately. Use a scan tool or infrared thermometer to check actual coolant temperature. If over 240F, stop driving and let the engine cool.
Why is the hot lamp important?
The engine hot lamp is a critical safety warning. Without it, you may not notice overheating, which can cause head gasket failure or engine seizure.
Can I just watch the temperature gauge instead?
While the gauge provides information, the warning lamp is designed to be an unmistakable alert. Repair it to ensure you are always warned of dangerous temperatures.