Failed or degraded catalytic converter heater element, which is the most common cause on high-mileage vehicles; Damaged or corroded wiring and connector terminals between the heater and the control module; Open or shorted heater circuit caused by road debris, heat damage, or chafing; A control module driver circuit that is weak or failing, though this is less common; Poor ground connection for the heater circuit, leading to excessive voltage drop; Aftermarket or incorrect catalytic converter assembly with a heater that does not match the original specifications

DTC codes / P04xx · Auxiliary emission controls / P04FF

P04FFCatalyst Heater Circuit Performance Bank 2

Q: What does code P04FF mean?

Catalyst Heater Circuit Performance Bank 2. P04FF indicates that the powertrain control module has detected a performance fault in the heater circuit for the bank 2 catalytic converter, which is the converter on the side of the engine that does not contain cylinder number one. The computer monitors the heater element's electrical current and response time during cold starts, and it sets this code when the heater does not warm the catalyst as quickly or as effectively as the stored model expects.

P04FF indicates that the powertrain control module has detected a performance fault in the heater circuit for the bank 2 catalytic converter, which is the converter on the side of the engine that does not contain cylinder number one. The computer monitors the heater element's electrical current and response time during cold starts, and it sets this code when the heater does not warm the catalyst as quickly or as effectively as the stored model expects.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaAuxiliary emission controls

Symptoms you may notice

Illumination of the check engine light, often with no other noticeable symptoms
A slightly longer than normal period of elevated cold-start emissions, which the driver cannot feel
In rare cases, a pending fault that clears itself after a few drive cycles if the heater circuit intermittently performs
No change in engine power, fuel economy, or driveability in most instances
Possible secondary code for catalyst efficiency if the heater fault persists and the converter never reaches operating temperature

Common causes, most likely first

Failed or degraded catalytic converter heater element, which is the most common cause on high-mileage vehicles
Damaged or corroded wiring and connector terminals between the heater and the control module
Open or shorted heater circuit caused by road debris, heat damage, or chafing
A control module driver circuit that is weak or failing, though this is less common
Poor ground connection for the heater circuit, leading to excessive voltage drop
Aftermarket or incorrect catalytic converter assembly with a heater that does not match the original specifications

How to diagnose and fix it

Scan all modules and record freeze-frame data for P04FF and any related codes before clearing anything
Visually inspect the bank 2 converter heater connector, wiring, and ground points for corrosion, chafing, or heat damage
Measure the heater element resistance with a multimeter and compare it to the manufacturer's specification
Check for voltage and ground at the heater connector during a cold-start command using a scan tool or a test light
Perform a voltage drop test on both the power and ground sides of the heater circuit under load
If the circuit tests good, command the heater on with a scan tool and verify current draw with a low-current clamp
Replace the catalytic converter assembly only after confirming the heater element itself is open or out of specification

What the heater circuit test really shows

A heater element can pass a simple resistance check when cold yet still fail to draw enough current when commanded on, so a current clamp test is more reliable than a multimeter alone.
The bank 2 designation refers to the side of the engine opposite cylinder number one, and on V-configuration engines this is often the harder converter to access, which leads to skipped inspections.
A weak battery or charging system can cause the control module to abort the heater test and set a performance code without any actual heater fault, so always check system voltage first.
Aftermarket converters sometimes use a heater with a different resistance curve, and the control module may set P04FF even though the new part works, simply because the feedback does not match the stored model.
The code does not always mean the converter is failing; a poor ground shared with another circuit can pull the heater voltage down just enough to trigger the performance monitor.

Can I keep driving with P04FF?

You can usually continue driving with P04FF because the fault mainly affects cold-start emissions and does not create a safety risk, but avoid long periods of short trips that never let the converter warm up, and have the circuit inspected soon to prevent a more expensive converter failure.

Tools that help

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