P2056: Reductant Injection Valve Circuit/Open (Bank 2 Unit 2)

P2056 refers to the fourth possible DEF injector position: the second valve in the Bank 2 exhaust line. It requires both a twin-bank layout and two dosing points per bank, a combination hardly any production engine uses; no manufacturer publicly documents the code. Detection would resemble GM's open-load check for metering valve 2 in its 2025 table (P2053): driver status read every 100 ms, more than 11 V on board, 30 bad samples out of 60, Type A. CARB lists reductant system valves among the electrical components whose circuits the OBD system has to verify. Before condemning a part, confirm which physical injector the scan tool assigns to Bank 2, unit 2, because confusing banks and units is an easy way to replace the wrong valve.

Medium severity. Can I keep driving?Deal with it soon. If the instrument cluster shows a countdown, the car may not restart once it reaches zero.

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

Symptoms

MIL on
Reduced NOx conversion on Bank 2

Most likely causes

Connector of the Bank 2 second injector unplugged or corroded
Broken wire in the Bank 2 dosing harness
Open injector coil

What to check, in order

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

Check the AdBlue/DEF level and quality, and do not add additives or water
Check the continuity of the wire between the component and the control module.
Look for white crystals around the injector and the tank
Check connectors and heaters with the scanner
Run the dosing test available on your diagnostic tool
Replace parts only when the test points to that component

Good to know

Repair difficulty: medium
It can trigger limp mode.
It affects emissions.

What each character of P2056 means

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

Frequently asked questions

Can I keep driving with code P2056?

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

What causes code P2056?

The most common causes are: connector of the Bank 2 second injector unplugged or corroded; broken wire in the Bank 2 dosing harness; open injector coil.

Related codes

Sources

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.