P20F0: SCR NOx Catalyst Over Temperature (Bank 2)

What it means

SCR NOx Catalyst Over Temperature (Bank 2): the component is overheating, typically from extended load or slip.

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test
• The engine or gearbox may go into limp mode

How it works

The SCR catalyst in bank 2 treats nitrogen oxides in the exhaust using injected reductant. The control module monitors its temperature from exhaust sensors or a calculated value. This code sets when the bank 2 catalyst temperature exceeds the allowed limit under monitor conditions.

Common causes

Most likely first.

1. Runaway DPF regeneration upstream
2. Temperature sensor drift high

Symptoms

• Check engine light on
• Failed emissions inspection
• Possibly slightly increased fuel consumption
• Sulfur (rotten egg) smell from exhaust under load

How to diagnose it

1. Read freeze-frame data and live bank 2 exhaust-temperature readings to determine when the catalyst was judged too hot.
2. Compare bank 2 temperature sensor data with other exhaust temperature readings to check for a sensor drifting high.
3. Inspect bank 2 temperature-sensor wiring and connectors for heat damage, corrosion, or a poor connection.
4. Check for DPF regeneration, engine overheating, dosing, and exhaust restriction codes that could point to the source of excess temperature.
5. Inspect the bank 2 SCR catalyst and exhaust path for restriction or heat damage, and verify dosing against the manufacturer's specification.

Common fixes

• Repair damaged bank 2 temperature-sensor wiring or connections.
• Replace a bank 2 exhaust-temperature sensor confirmed to read high inaccurately.
• Correct a runaway or abnormal DPF regeneration or other upstream source of excessive exhaust heat.
• Repair an exhaust restriction or reductant-dosing fault identified during diagnosis.
• Replace the bank 2 SCR catalyst if it is confirmed heat damaged after upstream causes are addressed.

Can I keep driving?

Avoid heavy acceleration, towing, and long trips because continued overheating can damage the bank 2 catalyst and may trigger reduced power. If the vehicle enters limp mode or displays a severe exhaust warning, stop when safe and arrange assistance.