Open circuit, short to ground or short to voltage in the wiring between the module and the instrument cluster lamp; Corroded, loose or damaged connector terminals at the module or instrument cluster; Faulty instrument cluster or failed lamp driver or bulb circuit within it; Fault in the engine coolant temperature sensor circuit causing the lamp to be commanded incorrectly; Internal fault in the powertrain control module output driver; Genuine engine overheating or low coolant level triggering the lamp command.

P1673

Engine Hot Lamp Control Circuit.

GM
Powertrain
Manufacturer code
Medium severity

How this code is built

P: SystemPowertrain
1: Defined byThe manufacturer
6: AreaComputer and output circuits
73: FaultThe specific fault in that area

What it means

P1673 on GM vehicles means the powertrain control module has detected a fault in the control circuit for the engine hot (temperature warning) lamp in the instrument cluster. The module commands the lamp on or off and monitors the circuit, and it set the code because the circuit voltage did not match what it expected. This points to a problem with the lamp circuit rather than necessarily with the engine actually overheating.

Symptoms

Engine hot or temperature warning lamp stays on constantly
Engine hot lamp does not light at all during the bulb check at ignition on
Lamp flickers or comes on intermittently
Malfunction indicator lamp may be on with the code stored
Temperature gauge reading may or may not agree with the warning lamp

Possible causes

Open circuit, short to ground or short to voltage in the wiring between the module and the instrument cluster lamplikely
Corroded, loose or damaged connector terminals at the module or instrument clusterlikely
Faulty instrument cluster or failed lamp driver or bulb circuit within itpossible
Fault in the engine coolant temperature sensor circuit causing the lamp to be commanded incorrectlypossible
Internal fault in the powertrain control module output driverrare
Genuine engine overheating or low coolant level triggering the lamp commandpossible

How to diagnose

Read all stored and pending codes and note the freeze frame data, checking for any coolant temperature sensor codes alongside P1673
Check the coolant level when the engine is cold and compare the gauge reading with a scan tool coolant temperature value to rule out real overheating
Watch the engine hot lamp during the ignition-on bulb check and note whether it lights, stays on or stays off
Inspect the wiring and connectors at the instrument cluster and powertrain control module for damage, corrosion, pushed-out pins or water ingress
Check the lamp circuit for continuity, short to ground and short to voltage using the wiring diagram for the specific model and year
Use the scan tool bi-directional controls, if supported, to command the lamp on and off and see if the cluster responds
Check the powertrain control module and cluster power and earth supplies and related fuses
Check for any technical service bulletins or calibration updates for the specific model and engine

How to fix

Repair or replace damaged wiring in the lamp control circuit
Clean or replace corroded or loose connector terminals at the module and cluster
Repair or replace the instrument cluster if the lamp driver circuit is faulty
Repair any coolant temperature sensor or wiring fault found, and correct any real cooling system problem such as low coolant
Replace or reprogram the powertrain control module only after the wiring and cluster are proven good, and only if an updated calibration or a fault is confirmed

Can I keep driving?

Medium severity

If the engine is not actually overheating, the car can be driven short-term, but the warning lamp may not be reliable so watch the temperature gauge closely. Get it checked soon, and stop at once if the gauge shows high temperature or you see steam or coolant loss.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.