Open circuit or poor connection in the wiring between the engine control module and the instrument cluster lamp; Short to ground or short to voltage in the lamp control wire; Corroded or loose connector terminals at the module or instrument cluster; Faulty instrument cluster or failed lamp driver or bulb; Fault inside the engine control module lamp driver output; Previous wiring repair or aftermarket accessory wiring interfering with the circuit.

P1673

Engine Hot Lamp Control Circuit.

GMC
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 GMC means the engine control module has detected a fault in the control circuit for the engine hot (overtemperature) warning lamp. The module commands the lamp on and off and monitors the circuit, and it saw a voltage or state that did not match the command, such as an open circuit, short to ground or short to voltage. The code points to the lamp circuit, not necessarily to the engine actually overheating.

Symptoms

Engine hot warning lamp stays on, or never lights
Lamp does not light briefly during the bulb check at ignition on
Check engine lamp or service message may be displayed
Temperature gauge reading may be normal while the lamp misbehaves
Intermittent lamp operation when driving over bumps

Possible causes

Open circuit or poor connection in the wiring between the engine control module and the instrument cluster lamplikely
Short to ground or short to voltage in the lamp control wirelikely
Corroded or loose connector terminals at the module or instrument clusterpossible
Faulty instrument cluster or failed lamp driver or bulbpossible
Fault inside the engine control module lamp driver outputrare
Previous wiring repair or aftermarket accessory wiring interfering with the circuitrare

How to diagnose

Read all stored codes and freeze frame data, and note whether other cooling system or coolant temperature codes are present
Check the actual engine temperature against the gauge and a scan tool coolant temperature reading to confirm the engine is not really overheating
Observe the hot lamp during the ignition-on bulb check and see whether it matches the commanded state
Visually inspect the wiring harness and connectors between the engine control module and the instrument cluster for chafing, water ingress, corrosion and damage
Check the coolant level and condition, as a genuine overheating condition should be ruled out first
Using the wiring diagram for the specific model and year, test the lamp control wire for continuity, short to ground and short to voltage
Check the supply and ground to the instrument cluster and confirm the lamp or its driver works
Command the lamp with a bidirectional function if available, to see whether the module output responds

How to fix

Repair or replace damaged wiring and restore the circuit to specification
Clean, tighten or replace corroded or loose connector terminals
Replace the failed bulb or repair or replace the instrument cluster if the lamp driver is faulty
Replace or repair the engine control module only after wiring and cluster have been proven good, and have it programmed as required for the model
Remove any faulty aftermarket wiring and clear the codes, then confirm the fault does not return

Can I keep driving?

Low severity

If the engine temperature is confirmed normal, the vehicle can usually be driven and booked in for repair. Keep a close eye on the temperature gauge, because the warning lamp may not be reliable to warn you of overheating.

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