P205F: Reductant System Performance (Bank 2)

P205F is the Bank 2 version of the reductant system performance check, meant for engines in which the second cylinder bank has its own SCR branch with separate pressure supply or valve. It applies when that branch is electrically sound but fails to reach or regulate the pressure or quantity the controller asks for. No manufacturer publicly documents P205F; even a V-engine such as Ram's 3.0 L EcoDiesel V6 lists delivery problems as P204F in its bulletins. The Bank 1 logic gives orientation: GM's 6.6 L LML waits for 30 failed build-up attempts below 350 kPa before setting a Type A code. CARB requires every SCR system to detect delivery faults before emissions exceed the limits. Look for blocked lines, a sticking valve or crystallised DEF in the second branch.

Bank 2 is the side without cylinder 1, so it only exists on V or boxer engines.

Symptoms

• MIL and DEF warning on
• Higher NOx from Bank 2, possible inducement

Most likely causes

• Blocked or frozen DEF line to the Bank 2 branch
• Bank 2 injector sticking due to DEF crystals
• Insufficient pump or metering unit pressure for the second branch

What to check, in order

Start with the simplest. You can tick off each step.

1. Check the AdBlue/DEF level and quality, and do not add additives or water
2. Compare the reading with other engine data while varying the engine speed.
3. Look for white crystals around the injector and the tank
4. Check connectors and heaters with the scanner
5. Run the dosing test available on your diagnostic tool
6. Replace parts only when the test points to that component

Good to know

• Repair difficulty: hard
• It can trigger limp mode.
• It affects emissions.

What each character of P205F means

• P: Powertrain: engine and transmission
• 2: Generic code: same on every make
• 0: Subsystem depends on the code range
• 5F: Specific fault in that system

Frequently asked questions

Can I keep driving with code P205F?

Deal with it soon. If the instrument cluster shows a countdown, the car may not restart once it reaches zero.

What causes code P205F?

The most common causes are: blocked or frozen DEF line to the Bank 2 branch; bank 2 injector sticking due to DEF crystals; insufficient pump or metering unit pressure for the second branch.

Related codes

• P204FReductant System Performance (Bank 1)
• P20E8Reductant Pressure Too Low
• P20E9Reductant Pressure Too High
• P201AReductant Injection Valve Circuit Range/Performance (Bank 2 Unit 1)

Sources

• law.cornell.edu: 13 CCR 1968.2
• gsi.ext.gm.com: 14OBDG10 Engine Diagnostics
• static.nhtsa.gov: MC 10220589 9999

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.