P204F code meaning
Reductant System Performance (Bank 1)
Powertrain system Generic code P20xx codes Check engine light
What P204F means
P204F (Bank 1) is the functional check of the whole DEF delivery path: the parts are electrically intact, yet the system cannot build or hold the pressure needed for dosing. GM's 6.6 L LML stores a Type A code if the pump module stays at or below 350 kPa after 30 build-up and venting attempts of at least 10 s each; the 2014 Cruze diesel uses 375 kPa and 20 attempts. GM treats P204F as a tamper fault. On Hino trucks P204F is the engine ECU's summary code for urea SCR faults seen by the dosing unit; per TT-14-025 it clears only after the DCU faults are repaired and the SCR memory has been reset. Ram's 3.0 L V6 EcoDiesel received PCM updates covering it (18-008-21). CARB demands this delivery check. Causes include frozen or clogged lines, a worn pump, air leaks or an empty tank.
P204F at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyHard
- Typical labor1 to 6 hours
- Clears after repairAfter a drive cycle
Symptoms of P204F
- MIL and DEF warning on
- Countdown to speed or power limitation
- Code returns after clearing until the cause is fixed
Common causes of P204F
- Most likelyDEF line clogged by crystals or frozen
- PossibleWorn DEF pump that cannot reach target pressure
- PossibleAir leak on the suction side or loose line couplings
- PossibleDosing unit faults repaired but SCR memory not reset (Hino)
- Less likelyControl module software needing an update (Ram 3.0 L)
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Reductant pumpReductant pressure sensorReductant linesReductant injection valve
What each part of P204F 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. |
| 4F | The exact fault in that area. |
What to do next
- Note P204F 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 P204F
What does P204F mean?
P204F means "Reductant System Performance (Bank 1)". P204F (Bank 1) is the functional check of the whole DEF delivery path: the parts are electrically intact, yet the system cannot build or hold the pressure needed for dosing. It is a generic code, so it means the same on every make.
Is it safe to drive with P204F?
Drive gently and only to a workshop. With P204F the car can go into limp mode (reduced power) to protect itself.
Will P204F fail an emissions test?
Yes, it can. P204F 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 P204F to fix?
Difficulty: hard. A typical repair takes 1 to 6 hours of work. This is a job for a workshop.
Will P204F clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.