Open or damaged wiring in the reductant tank heater control circuit, such as a broken wire or corroded connector; Failed reductant tank heater element, typically an open internal circuit in the heating coil; Poor electrical connection at the heater or control module connector, including loose pins or water intrusion; Blown fuse or faulty relay that supplies power to the reductant tank heater circuit; Faulty reductant control module or powertrain control module driver circuit, though less common; Corrosion or damage to the heater circuit caused by exposure to road debris, salt, or urea leakage

DTC codes / P20xx · Fuel and air metering and auxiliary emission controls / P202A

P202AReductant Tank Heater Control Circuit/Open

Q: What does code P202A mean?

Reductant Tank Heater Control Circuit/Open. P202A indicates that the powertrain control module has detected an open circuit or abnormal voltage on the control circuit for the reductant tank heater, which is the heating element used to keep diesel exhaust fluid from freezing in cold weather. The computer monitors the commanded heater state against the expected current draw and sets this code when the circuit does not respond as designed, typically because of a broken wire, failed heater element, or poor connection.

P202A indicates that the powertrain control module has detected an open circuit or abnormal voltage on the control circuit for the reductant tank heater, which is the heating element used to keep diesel exhaust fluid from freezing in cold weather. The computer monitors the commanded heater state against the expected current draw and sets this code when the circuit does not respond as designed, typically because of a broken wire, failed heater element, or poor connection.

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 pending or stored P202A code with no drivability complaints in mild weather
Extended crank times or a no-start condition in freezing temperatures if the heater is inoperative
Reductant system-related warnings or messages on the driver information display
Possible reduction in engine power or activation of limp mode if the fault escalates
Increased diesel exhaust fluid consumption or poor selective catalytic reduction efficiency in cold climates

Common causes, most likely first

Open or damaged wiring in the reductant tank heater control circuit, such as a broken wire or corroded connector
Failed reductant tank heater element, typically an open internal circuit in the heating coil
Poor electrical connection at the heater or control module connector, including loose pins or water intrusion
Blown fuse or faulty relay that supplies power to the reductant tank heater circuit
Faulty reductant control module or powertrain control module driver circuit, though less common
Corrosion or damage to the heater circuit caused by exposure to road debris, salt, or urea leakage

How to diagnose and fix it

Perform a visual inspection of the reductant tank heater wiring and connectors for damage, corrosion, or loose pins
Check the fuse and relay that supply power to the reductant tank heater circuit and replace if faulty
Measure resistance across the heater element with a multimeter and compare to the manufacturer's specification to confirm an open circuit
Backprobe the control circuit at the heater connector and command the heater on with a scan tool to verify voltage and ground signals
Check for continuity and voltage drop on the control circuit between the heater and the control module to isolate an open or high-resistance wire
If the circuit and heater test good, diagnose the control module output driver or replace the module as required
Clear the code and perform a road test or actuation test to confirm the repair and ensure the heater operates correctly

What most technicians overlook on P202A

A failed reductant tank heater often sets no drivability symptoms in warm weather, so the code may be overlooked until a cold snap causes a no-start or derate condition.
The heater element can test good at room temperature but fail open when cold, so resistance checks should be repeated after chilling the component if the fault is intermittent.
Water intrusion or urea crystal buildup in the heater connector is a common cause of an open circuit that a simple wiggle test may not reveal.
Some vehicles use a pulse-width-modulated control signal for the heater, so a basic test light may give misleading results; a duty-cycle-capable meter or oscilloscope is needed.
A weak or failing battery can cause the control module to set false open-circuit codes on heater circuits, so always verify battery condition and charging voltage first.

Can I keep driving with P202A?

You can generally continue driving in mild weather because the heater is only needed to prevent the reductant from freezing, but avoid long trips in freezing conditions until repaired. If the check engine light begins flashing or the vehicle enters limp mode, stop driving and seek service immediately.

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.