P204E
Pressure Sensor Circuit Intermittent/ErraticP204E is a generic OBD-II powertrain diagnostic trouble code: Pressure Sensor Circuit Intermittent/Erratic. It is logged by the engine control unit when the powertrain monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.
What P204E means
P204E is stored when the SCR after-treatment control module determines that the DEF injection valve is stuck in the open position. The control module infers valve position from a combination of DEF flow rate feedback, dosing pressure, and the upstream and downstream NOx sensor signals. When the valve cannot close on command, DEF continues to flow into the exhaust stream beyond the required quantity, leading to ammonia slip past the SCR catalyst and potential catalyst damage from ammonia saturating the catalyst washcoat.
A stuck-open injector can also deposit excess urea in the exhaust pipe and diesel particulate filter upstream of the SCR, which can cause urea decomposition products to accumulate and block the DPF or SCR catalyst inlet. On many platforms, the module will disable the DEF dosing system entirely and illuminate the SCR warning lamp alongside the MIL to prevent further over-dosing.
Mechanical sticking is the most common cause, typically due to urea crystal deposits jamming the valve needle in the open seat, or a solenoid that has lost sufficient closing force. Electrical diagnosis should confirm the solenoid is not being permanently energized before condemning the valve mechanically.
Common causes
Most-frequently reported root causes when P204E is logged.
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1
Urea crystal deposits on the injector needle seat preventing the valve from closing.
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2
Solenoid return spring weakened or broken, reducing closing force.
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3
Control module or wiring fault permanently energizing the solenoid command signal.
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4
Contaminated DEF fluid leaving heavy deposits that jam the needle open.
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5
Corrosion or mechanical damage to the injector body preventing needle travel.
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6
Heat damage to the solenoid coil from exhaust proximity, reducing magnetic closing force.
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7
DEF rail pressure abnormally high, overpowering the spring closing force.
Symptoms drivers notice
How to diagnose P204E
A typical diagnostic flow when this code is present.
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1
Retrieve all DTCs and review freeze frame; confirm the fault is not accompanied by a wiring short that could be keeping the solenoid energized.
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2
With the engine off and DEF system depressurized, command the injector valve closed via the scan tool and verify DEF pressure drops as expected.
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3
Inspect the DEF injector electrical connector; confirm there is no voltage on the signal wire when the valve is not commanded open.
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4
Remove the DEF injector and inspect the needle seat area for urea crystallization deposits.
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5
Attempt to clean the injector tip with warm water per the service procedure; test valve operation before reinstalling.
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6
If cleaning does not restore proper closure, replace the DEF injection valve.
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7
After replacement, perform a DEF system leak check and verify dosing quantity with the scan tool.
Related powertrain codes
- P2000 — NOx Adsorber Efficiency Below Threshold Bank 1
- P2001 — NOx Adsorber Efficiency Below Threshold Bank 2
- P2002 — Diesel Particulate Filter Efficiency Below Threshold Bank 1
- P2003 — Diesel Particulate Filter Efficiency Below Threshold Bank 2
- P2004 — Intake Manifold Runner Control Stuck Open Bank 1
- P2005 — Intake Manifold Runner Control Stuck Open Bank 2
Frequently asked questions
Can I clean a stuck-open DEF injector rather than replacing it?
Mild urea crystal deposits can sometimes be dissolved by soaking the tip in warm water. However, if the needle or seat is mechanically damaged, cleaning will not restore full closure.
What damage can a stuck-open DEF injector cause?
Excess urea deposits can accumulate in the exhaust system and block the DPF or SCR catalyst, and ammonia slip can contaminate downstream sensors. Early repair prevents expensive catalyst or filter replacement.
Does P204E always mean the injector is mechanically stuck?
No. First confirm the solenoid is not being held open by a wiring or control module fault. If the solenoid is electrically normal but the valve still does not close, the fault is mechanical.
Will DEF quality affect whether P204E occurs?
Yes. Using off-specification DEF with higher urea concentration or contaminants increases the risk of crystal deposits forming on the injector needle, which is a common cause of mechanical sticking.
Disabling P204E in software
RaceTune can permanently disable P204E — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.
ECUs with a P204E disable in our catalogue
Confirmed coverage from our recipe database — we support many more families. Upload your file and our identifier will match it automatically.
- Bosch EDC17C60 verified 1 software version
Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.
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