P20F7

Code

Generic P — Powertrain

Reductant Injection Valve Stuck Open Bank 2 Unit 1

Brand: Generic

Type: P — Powertrain

Views: UK: 26 EN: 34 RU: 26

AI status

Completed

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Completed 100%

Page language: EN

Causes

Reductant injection valve mechanically stuck open (crystallized/blocked by dried urea deposits)
Valve solenoid electrical short or stuck actuator
Contaminated or blocked reductant lines or filter causing valve to hang open
Wiring harness connector corrosion, short-to-ground, or short-to-voltage
Faulty injector driver or engine control module (ECM)
Low or contaminated reductant (DEF) quality causing deposits

Symptoms

Malfunction Indicator Lamp (MIL) or check-engine light on
Rapidly dropping DEF level or unexpectedly low reservoir level
Excess ammonia (NH3) slip or strong odor from exhaust
SCR efficiency fault, increased NOx emissions or failed emissions test
Possible DTCs related to SCR/reductant system and injectors
Visible DEF leaks or puddling under vehicle near injector area (in some cases)

What to check

Retrieve all stored codes and freeze-frame data with a scan tool; note operating conditions when fault occurred
Visually inspect DEF tank level, quality (contamination, discoloration), and supply lines for leaks or crystals
Inspect connector at the reductant injection valve for corrosion, bent pins, or moisture ingress
Perform an active command (bi-directional test) to open and close the valve while watching scan tool feedback
Measure valve coil resistance and compare to manufacturer specification
Backprobe the valve connector and check for proper control voltage/PWM and ground while commanding the valve

Signal parameters

Valve coil resistance (typical solenoid range ~10–40 ohms — check manufacturer spec)
Control voltage to valve: 0–12 V (may be switched or PWM)
Command signal: duty cycle 0–100% when PWM-controlled
Operating current when energized: ~0.1–2.5 A (depending on design)
Injector open/closed state feedback (if equipped) or expected change in reductant flow when commanded
DEF system pressure or pump output when injector should be closed vs. open

Diagnostic algorithm

Retrieve and record DTCs and freeze-frame data. Check for related SCR/NOx codes.
Visually inspect DEF tank, lines, filter, and injector area for leaks, crystallization or contamination. Replace contaminated DEF and clean crystals before further testing.
Check connector and wiring: unplug valve connector, inspect pins for corrosion or damage, wiggle-test harness while monitoring for intermittent faults.
Measure valve coil resistance with ohmmeter; compare with spec. An open or very low resistance indicates coil failure.
With a scan tool, perform an active test: command the valve closed and open. Observe reductant flow (if visible), pressure/flow parameters, and monitor current draw/waveform. A valve that cannot close or shows constant flow when commanded closed is likely stuck mechanically.
Backprobe connector while commanding valve: verify proper control voltage/PWM and reliable ground. If control signals are correct but valve does not respond, suspect valve mechanical failure.
If wiring or connector faults are found, repair/replace damaged harness or connector and re-test. If electrical signals are missing, trace to ECU and check injector driver outputs.
If valve is confirmed stuck or mechanically failed, replace the reductant injection valve and any contaminated filters or lines. Clean surrounding deposits and flush lines per manufacturer service instructions.
After repairs, clear codes, top up with clean OEM-spec DEF, perform active tests and a road test to confirm normal operation and that no new codes return. Re-scan to ensure SCR system parameters are within expected ranges.
If replacement valve does not correct the fault and wiring/connector are good, consider ECU/driver module diagnosis or reflashing per manufacturer guidance.

Likely causes

Urea crystallization or contamination causing the injector to stick open
Wiring connector corrosion or short in the valve circuit
Solenoid coil or internal actuator failure
Clogged valve body or nozzle preventing proper seating
Faulty ECU/injector driver (less common)

Fault status

⚠️ Status

Reductant injection valve (Bank 2, Unit 1) detected stuck open — continuous or unintended reductant flow when valve should be closed. Inspect valve, wiring, and DEF system components.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.5-3.0 hours