What does it mean?
P1673 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Engine Hot Lamp Control Circuit Malfunction .
Symptoms
- The overheat warning lamp never lights during the ignition bulb check
- Or it stays lit continuously while the coolant temperature is normal
- MIL on, with no change in engine performance
- The real danger is that a genuine overheating condition is never shown to the driver
- Other cluster warning lamps may be affected at the same time
Likely causes
- Overheat indicator bulb or LED failed in the instrument cluster
- Open or shorted control wire between the control module and the cluster
- Corroded or loose cluster connector terminals
- Internal failure of the cluster indicator circuit
- Failed lamp output driver in the control module
- Blown instrument panel fuse
- A replacement cluster that does not match the vehicle specification
How to fix it
- Watch the cluster during the ignition-on bulb check to see whether the lamp can illuminate at all
- Compare the coolant temperature on scan tool live data with the gauge reading and the lamp state
- Check the instrument panel fuse and the cluster power and ground feeds
- Unplug and inspect the cluster connector for corrosion, bent pins and weak terminal tension
- Test the control wire between module and cluster for continuity and for shorts to ground and battery voltage
- Replace a burnt bulb or repair the cluster indicator circuit
- While the lamp is unreliable, monitor coolant temperature with a scan tool so a real overheat is not missed, and check the cooling system condition