Rich fuel mixture from a leaking or stuck-open fuel injector; Misfiring engine sending unburned fuel into the exhaust; Failed ignition coil, spark plug, or spark plug wire causing incomplete combustion; Faulty oxygen sensor reporting incorrect mixture and causing over-fueling; Restricted exhaust flow from a collapsed converter substrate or damaged pipe; Engine coolant temperature sensor fault causing the PCM to command a rich mixture; Excessive oil consumption or coolant intrusion burning in the exhaust

DTC codes / GM codes / P1484

P1484 · GMCatalytic Converter Overheat Detected

Q: What does code P1484 mean?

Catalytic Converter Overheat Detected. P1484 on GM vehicles indicates that the powertrain control module has detected conditions consistent with an overheated catalytic converter, typically by monitoring exhaust temperature or oxygen sensor behavior. The computer is flagging a thermal event that can melt the converter substrate and damage surrounding components if ignored.

P1484 on GM vehicles indicates that the powertrain control module has detected conditions consistent with an overheated catalytic converter, typically by monitoring exhaust temperature or oxygen sensor behavior. The computer is flagging a thermal event that can melt the converter substrate and damage surrounding components if ignored.

SystemPowertrain

Code typeGM specific

SeverityHigh

Fix difficultyProfessional

AreaAuxiliary emission controls

Symptoms you may notice

Illuminated check engine light, often with no other noticeable symptoms
Rotten egg sulfur smell from the exhaust after driving
Rattling or buzzing noise from under the vehicle at idle or during acceleration
Reduced engine power or poor fuel economy in severe cases
Heat discoloration or glowing converter body visible underneath at night
In rare cases, a burning smell or smoke from the floorboard area

Common causes, most likely first

Rich fuel mixture from a leaking or stuck-open fuel injector
Misfiring engine sending unburned fuel into the exhaust
Failed ignition coil, spark plug, or spark plug wire causing incomplete combustion
Faulty oxygen sensor reporting incorrect mixture and causing over-fueling
Restricted exhaust flow from a collapsed converter substrate or damaged pipe
Engine coolant temperature sensor fault causing the PCM to command a rich mixture
Excessive oil consumption or coolant intrusion burning in the exhaust

How to diagnose and fix it

Scan all modules for stored and pending codes, especially misfire and fuel trim codes, before touching the converter
Inspect spark plugs, ignition coils, and wires for signs of misfire or fouling
Check live fuel trim data to confirm whether the engine is running rich
Test oxygen sensors and coolant temperature sensor with a scan tool and multimeter
Perform a backpressure test on the exhaust system to rule out a restricted converter or pipe
Verify injector operation and check for leaking injectors with a fuel pressure leak-down test
Replace the catalytic converter only after correcting the root cause, then clear codes and verify readiness monitors

Before you replace the catalytic converter

A converter that overheats is almost always a victim of another fault, so replacing it without fixing the rich mixture or misfire will destroy the new unit in short order.
GM vehicles often set P1484 alongside misfire codes that the driver never felt, so a scan tool history check is more reliable than seat-of-the-pants diagnosis.
A restricted exhaust can mimic converter overheat symptoms, so a backpressure test is cheaper and faster than swapping parts.
Some aftermarket or universal converters run hotter than the original unit and can trigger this code even when the engine is running correctly.
The PCM may set P1484 based on calculated exhaust temperature rather than a dedicated sensor, so a failed oxygen sensor can falsely trigger the code.

Can I keep driving with P1484?

Limit driving to a short trip to a repair shop and avoid heavy throttle or sustained high speeds, because an overheating converter can melt internally and cause a costly exhaust restriction or fire risk.

Tools that help

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Guidance is general and written for GM vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.