HomeTrouble CodesP2057

P2057 — Reductant Injection Valve Circuit Low Bank 2 Unit 2

Manufacturer-specificPowertrain (engine & transmission)

This code indicates the engine control module has detected a lower than expected voltage condition in the circuit for the Diesel Exhaust Fluid (DEF) injector on bank 2, unit 2. This specific injector is part of the Selective Catalytic Reduction (SCR) system used to reduce nitrogen oxide emissions in diesel engines. The issue is typically electrical, involving the injector itself or the wiring harness connecting it to the control module.

Symptoms

What causes it — most likely first

1. Failed DEF injector assembly

Internal electrical shorts within the injector heater or valve are the most common cause of low voltage codes. Replacement is usually required to resolve the internal failure.

2. Damaged wiring harness

Wires near exhaust components often degrade due to heat exposure or chafing against engine parts. Insulation melting can expose conductors to ground causing low voltage.

3. Corroded electrical connector

Exposure to road salts and DEF fluid spills can cause terminal corrosion leading to poor contact. This increases resistance and drops circuit voltage.

4. DEF crystallization buildup

Hardened fluid around the injector tip can stress internal components and cause electrical faults. Leakage from the seal often contributes to connector corrosion.

5. Shorted circuit in wiring loom

Insulation failure within the main harness can cause the circuit voltage to drop below thresholds. Vibration over time often leads to wire fatigue and breaks.

6. Faulty engine control module

Internal driver failure within the PCM is possible but statistically rare compared to component failure. This should only be considered after all external circuits are verified.

How it's diagnosed

  1. Visually inspect the wiring harness and connector at the Bank 2 Unit 2 injector for physical damage or corrosion.
  2. Disconnect the injector and measure resistance across the terminals to check for internal shorts.
  3. Check continuity and voltage supply at the harness connector with the key on and engine off.
  4. Inspect the injector mounting area for signs of DEF leakage or crystallization.
  5. Repair any found wiring issues and clear codes to test system operation.
  6. Replace the injector if resistance values are outside of manufacturer specifications.

Code facts & related codes

SystemPowertrain (engine & transmission)
StandardizationManufacturer-specific (P1/B1/C1/U1)

Frequently asked

Is this code caused by a bad computer?

It is highly unlikely. Control module failure is rare for this code; the injector or wiring is the cause in the vast majority of cases.

Can I continue driving with this code?

Short-term driving is possible, but the vehicle may enter reduced power mode and will fail emissions inspections.

Will refilling the DEF tank fix this code?

No, this code indicates an electrical circuit fault, not a low fluid level condition.

Can the injector be cleaned instead of replaced?

Cleaning is generally not effective for internal electrical failures; replacement is the standard repair procedure.