P204F on Mazda
Reductant System Incorrect Quantity
P204F on Mazda vehicles indicates reductant system incorrect quantity. Au7o has documented this code across 1 Mazda model — most commonly on CX-60. This code is set on diesel SCR-equipped vehicles when the reductant (diesel exhaust fluid / DEF) system delivers an incorrect quantity of DEF, meaning the actual dosing or pressure doesn't match what the computer commanded. The reductant system pumps and injects DEF into the exhaust so the SCR catalyst can break down NOx emissions, and the computer monitors pressure and dosing performance. When it sees too much or too little fluid being delivered, or pressure that's out of range, it flags this performance code. Typical roots are a clogged or failing DEF pump, contaminated fluid, a faulty pressure sensor, or a bad injector.
Common Causes of P204F
- •Contaminated or poor-quality diesel exhaust fluid (DEF)
- •Faulty reductant (DEF) pressure sensor
- •Clogged DEF pump filter or weak/failing DEF pump
- •Faulty or clogged reductant injector
- •Leaking, cracked, or loose DEF lines/clamps
- •Crystallized DEF buildup blocking the system
- •Failed reductant/SCR control module
- •Wiring or connector faults in the reductant system
P204F on Mazda by Model
Mazda CX-60(1 issue)
- AdBlue (SCR) Overfull / False Warning Messages on Diesel2022-2025
Diesel CX-60 owners report AdBlue-related warnings appearing early (around 13,000 km) and, after topping up, an 'AdBlue overfull' or persistent low-AdBlue message even when the tank (~6.7 L usable) is filled correctly. Overfilling the urea tank can trigger the fault and, in some cases, risks damaging the SCR/urea system. Several owners found the warning self-cleared after roughly 1,000 km of driving without dealer intervention, indicating a sensor/level-reading calibration quirk rather than a true fault.
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View P204F across all makes →Frequently Asked Questions
What does P204F mean on Mazda?▼
P204F stands for "Reductant System Incorrect Quantity." This code is set on diesel SCR-equipped vehicles when the reductant (diesel exhaust fluid / DEF) system delivers an incorrect quantity of DEF, meaning the actual dosing or pressure doesn't match what the computer commanded. The reductant system pumps and injects DEF into the exhaust so the SCR catalyst can break down NOx emissions, and the computer monitors pressure and dosing performance. When it sees too much or too little fluid being delivered, or pressure that's out of range, it flags this performance code. Typical roots are a clogged or failing DEF pump, contaminated fluid, a faulty pressure sensor, or a bad injector. On Mazda specifically, this code is documented across 1 model.
What causes P204F on Mazda vehicles?▼
Common causes on Mazda: Contaminated or poor-quality diesel exhaust fluid (DEF), Faulty reductant (DEF) pressure sensor, Clogged DEF pump filter or weak/failing DEF pump, Faulty or clogged reductant injector, Leaking, cracked, or loose DEF lines/clamps. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P204F on a Mazda?▼
Repair costs vary widely depending on the root cause and specific Mazda model.
Which Mazda models have P204F documented?▼
Au7o has documented P204F on 1 Mazda model: CX-60.