P204E: Reductant Pressure Sensor Circuit Intermittent/Erratic

P204E covers a DEF pressure signal that jumps around although it stays inside the electrical limits, as with a loose terminal, a cracked wire or a sensor with an internal contact problem. GM's 2025 DEF controller is the public calibration: it adds up all absolute pressure changes over a moving window of 100 readings taken every 10 ms and counts a failure when that sum passes 1500 kPa while pumping forward, 1000 kPa when stopped or heating, or 200 kPa in reverse; ten failures within 100 runs store a Type A code. No other manufacturer documents the code in public. CARB expects input components to be checked for implausible as well as out-of-range signals. Besides the wiring, air in the line or a pump delivering unevenly can also make the pressure swing.

Symptoms

• MIL on, fault may come and go
• Dosing interrupted at times
• Accompanying DEF pump or pressure codes

Most likely causes

• Loose or fretted terminal at the pressure sensor connector
• Wire breaking intermittently under vibration
• Air in the DEF line or uneven pump delivery
• Pressure sensor with internal intermittent fault

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. Gently move the wiring with the engine running and watch whether the reading changes.
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: medium
• It can trigger limp mode.
• It affects emissions.

What each character of P204E means

• P: Powertrain: engine and transmission
• 2: Generic code: same on every make
• 0: Subsystem depends on the code range
• 4E: Specific fault in that system

Frequently asked questions

Can I keep driving with code P204E?

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

What causes code P204E?

The most common causes are: loose or fretted terminal at the pressure sensor connector; wire breaking intermittently under vibration; air in the DEF line or uneven pump delivery.

Related codes

• P204AReductant Pressure Sensor Circuit
• P204BReductant Pressure Sensor Circuit Range/Performance
• P204CReductant Pressure Sensor Circuit Low
• P204DReductant Pressure Sensor Circuit High

Sources

• gsi.ext.gm.com: 25OBDG04B
• law.cornell.edu: 13 CCR 1968.2

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.