P204D code meaning
Reductant Pressure Sensor Circuit High
Powertrain system Generic code P20xx codes Check engine light
What P204D means
P204D is the high-side counterpart: the pressure signal sits near or above the supply voltage, typically because the signal wire touches 5 V or battery voltage, the sensor ground is open, or the sensor has failed internally. Published limits are 4.80 V on GM's 6.6 L LML, 98 % of the supply in GM's 2018 diesel table, 4.90 V in GM's 2025 DEF controller and 4.85 V on Ford's 2023 diesels. GM's 2014 Cruze diesel logs it as Type B, the other GM tables as Type A. Deutz's EMR L1 calls the same state a short circuit to battery. To the controller such a reading could look like over-pressure, which is why it stops the pump; check the connector at the pump module and the sensor ground before replacing the module.
P204D at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyMedium
- Typical labor0.5 to 3 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P204D
- MIL on (after two trips on some GM diesels)
- DEF pump stopped, no dosing
- DEF warning and later inducement
Common causes of P204D
- Most likelyOpen sensor ground or corroded ground terminal
- PossibleSignal wire shorted to 5 V reference or battery voltage
- PossibleInternal failure of the pressure sensor in the pump module
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Reductant pressure sensor
What each part of P204D means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 0 | Area: fuel and air metering and auxiliary emission controls. |
| 4D | The exact fault in that area. |
What to do next
- Note P204D and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P204D
What does P204D mean?
P204D means "Reductant Pressure Sensor Circuit High". P204D is the high-side counterpart: the pressure signal sits near or above the supply voltage, typically because the signal wire touches 5 V or battery voltage, the sensor ground is open, or the sensor has failed internally. It is a generic code, so it means the same on every make.
Is it safe to drive with P204D?
Drive gently and only to a workshop. With P204D the car can go into limp mode (reduced power) to protect itself.
Will P204D fail an emissions test?
Yes, it can. P204D is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P204D to fix?
Difficulty: medium. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will P204D clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.