Open or blown bulb or faulty LED in the instrument cluster hot lamp circuit; Damaged, chafed or corroded wiring between the powertrain control module and the instrument cluster; Poor connection at the cluster or powertrain control module connector, such as loose, spread or corroded terminals; Fault inside the instrument cluster lamp driver or circuit board; Faulty powertrain control module output driver for the lamp; Wiring short caused by earlier repair work or water ingress.

P1673

Engine Hot Lamp Control Circuit.

Buick
Powertrain
Manufacturer code
Low 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 a Buick is a manufacturer-specific code for a fault in the Engine Hot Lamp control circuit. The powertrain control module drives the engine hot warning lamp and sets the code when the voltage it sees on that output does not match what it commanded, for example a short to ground, a short to voltage or an open circuit. It is a fault in the lamp circuit, not proof that the engine is actually overheating.

Symptoms

Engine hot warning lamp stays on, never comes on, or does not light during the bulb check at key-on
Engine hot lamp flickers or behaves erratically
Check engine lamp or service engine soon lamp on with P1673 stored
Temperature gauge reading may or may not agree with the lamp state
No other change in how the engine runs in most cases

Possible causes

Open or blown bulb or faulty LED in the instrument cluster hot lamp circuitlikely
Damaged, chafed or corroded wiring between the powertrain control module and the instrument clusterlikely
Poor connection at the cluster or powertrain control module connector, such as loose, spread or corroded terminalspossible
Fault inside the instrument cluster lamp driver or circuit boardpossible
Faulty powertrain control module output driver for the lamprare
Wiring short caused by earlier repair work or water ingresspossible

How to diagnose

Read all stored codes and freeze frame data, and note any coolant temperature or other cooling system codes alongside P1673
Check the coolant level when cold and confirm the engine is not actually running hot, comparing the gauge with a scan tool coolant temperature reading
Observe the engine hot lamp at key-on and note whether it lights, stays on or stays off
Inspect the wiring and connectors between the instrument cluster and the powertrain control module for chafing, corrosion, water and pin damage
Check the lamp circuit with a wiring diagram for the specific model and year, testing for short to ground, short to voltage and open circuit with the connectors disconnected
Verify the supply and ground to the instrument cluster, as the circuit layout varies by model
Use the scan tool bidirectional controls, if available for the model, to command the lamp on and off and compare the response
Clear the code after repair and road test to confirm it does not return

How to fix

Replace the failed bulb or lamp element where the cluster design allows it
Repair or replace damaged wiring and secure it clear of sharp edges and heat
Clean or repair corroded or loose terminals and reseat the connectors
Repair or replace the instrument cluster if the lamp driver is faulty
Replace or repair the powertrain control module only after wiring and cluster are proven good, following the model-specific procedure

Can I keep driving?

Low severity

The car can normally be driven while you book it in, as this is a lamp circuit fault. However, the lamp may not warn you of real overheating, so watch the temperature gauge closely and stop at once if the engine seems to run hot.

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