External leak from a cracked or damaged reductant tank, typically at seams or mounting points; Loose, chafed, or disconnected reductant line or fitting between the tank and the dosing injector; Failed reductant tank level sensor providing an erratic or falsely low reading that mimics a leak; Internal leak in the reductant pump module or pressure relief valve causing fluid to bypass or return incorrectly; Leaking or stuck-open reductant injector allowing fluid to dribble into the exhaust when not commanded; Crystallized urea blocking a vent or causing a seal to fail, leading to a slow leak; Damage to the reductant tank from road debris or improper jacking, creating a pinhole leak

DTC codes / P20xx · Fuel and air metering and auxiliary emission controls / P202D

P202DReductant Leakage

Q: What does code P202D mean?

Reductant Leakage. P202D indicates that the powertrain control module has detected a reductant leakage condition in the selective catalytic reduction system, typically by monitoring the reductant tank level sensor for an unexpected drop that cannot be explained by normal dosing. The computer compares the commanded reductant injection volume against the actual consumption rate derived from the tank level sensor and flags a leak when the consumption exceeds a calibrated threshold.

P202D indicates that the powertrain control module has detected a reductant leakage condition in the selective catalytic reduction system, typically by monitoring the reductant tank level sensor for an unexpected drop that cannot be explained by normal dosing. The computer compares the commanded reductant injection volume against the actual consumption rate derived from the tank level sensor and flags a leak when the consumption exceeds a calibrated threshold.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering and auxiliary emission controls

Symptoms you may notice

Illumination of the check engine light, often with no other noticeable symptoms
A warning message on the dashboard indicating low reductant level or a reductant system fault
Frequent need to refill the diesel exhaust fluid tank even when driving distance does not justify it
Possible activation of a speed limitation or engine derate if the leak is severe and the fluid level drops critically
Visible crystallized urea deposits or wet spots around the reductant tank, lines, or injector
A pungent ammonia smell near the vehicle after shutdown, especially in the engine bay or under the rear

Common causes, most likely first

External leak from a cracked or damaged reductant tank, typically at seams or mounting points
Loose, chafed, or disconnected reductant line or fitting between the tank and the dosing injector
Failed reductant tank level sensor providing an erratic or falsely low reading that mimics a leak
Internal leak in the reductant pump module or pressure relief valve causing fluid to bypass or return incorrectly
Leaking or stuck-open reductant injector allowing fluid to dribble into the exhaust when not commanded
Crystallized urea blocking a vent or causing a seal to fail, leading to a slow leak
Damage to the reductant tank from road debris or improper jacking, creating a pinhole leak

How to diagnose and fix it

Inspect the entire reductant system for external leaks: tank, lines, fittings, pump, and injector, looking for wet spots or white crystal deposits
Check the reductant tank level sensor operation with a scan tool by comparing the indicated level against a known refill volume
Pressure-test the reductant lines and components using the manufacturer's specified procedure to locate internal or external leaks
Verify that the reductant injector is not leaking by removing it and checking for dribbling or crystal formation on the tip
Repair or replace any leaking component, such as a cracked tank, damaged line, or faulty injector, using OEM parts
Clear the diagnostic trouble codes and perform a reductant system leak test or adaptation reset with a scan tool
Road-test the vehicle to confirm that the code does not return and that the reductant consumption rate is normal

What a reductant leak code really means

A faulty tank level sensor is a common cause of P202D because the computer interprets an erratic or low reading as a leak, even when no fluid is escaping.
Crystallized urea around a fitting or cap can indicate a slow seep that only appears under certain temperature or pressure conditions, so a visual inspection after a long drive is more revealing than a cold check.
The code can be set by a reductant injector that leaks internally, sending fluid into the exhaust stream without any external drip, which often leaves no visible trace on the ground.
A reductant tank that is overfilled can cause fluid to expand and leak through the vent, triggering the code without any component failure.
Some vehicles require a specific refill procedure or a scan-tool reset after adding reductant, and skipping this step can cause the level sensor to misreport and set a false leak code.

Can I keep driving with P202D?

You can usually continue driving short distances to a repair shop, but avoid long trips and keep the reductant tank topped up because a severe leak can lead to derate or speed limitation. Do not ignore the warning light, as continued driving with a leaking system may cause crystallized urea to damage other components.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.