The P202A: Reductant Tank Heater Control Circuit/Open code indicates an issue with the control circuit for the reductant (DEF/AdBlue) tank heater, such as an open circuit. This could be caused by a faulty heater control unit, wiring issues, or a damaged connector.
P202A – Quick Overview
Code | Information |
---|---|
Meaning | P202A: Reductant Tank Heater Control Circuit/Open |
Is it serious? | Yes, if the reductant tank heater fails, DEF fluid may freeze in cold weather, affecting the vehicle’s emission reduction system. |
Possible causes | – Open circuit in the reductant tank heater control – Faulty heater control – Wiring or connector issues |
How to diagnose? | – Inspect and test the heater control circuit – Check the heater control unit – Inspect wiring and connectors for damage |
P202A Meaning
The P202A: Reductant Tank Heater Control Circuit/Open code signifies that there is an issue with the control circuit of the reductant tank heater. The heater is responsible for warming the DEF (Diesel Exhaust Fluid) tank to prevent freezing in cold conditions, which is essential for the proper functioning of the emission control system. An open or faulty circuit can prevent the heater from working.
Step-by-step diagnostic guide
Action | Description | Tools Needed |
---|---|---|
Check for Other Codes | Use an OBD-II scanner to check for other related codes. Additional codes may provide further details on the root cause of the issue with the reductant system or heater. | OBD-II Scanner |
Inspect the Heater Control Circuit | Use a multimeter to test the control circuit for the reductant tank heater. Measure voltage and continuity in the circuit to detect any breaks or open circuits. | Multimeter |
Test the Heater Control Unit | Test the reductant tank heater control unit to ensure it is functioning properly. A faulty control unit can prevent the heater from receiving power, causing the open circuit issue. | Diagnostic Tool, Multimeter |
Inspect Wiring and Connectors | Visually inspect all wiring and connectors related to the heater control unit and the reductant tank heater. Look for signs of corrosion, damage, or disconnections that could cause an open circuit. | Flashlight, Multimeter |
Test Circuit Continuity | Perform a continuity test on the wiring leading to the reductant tank heater. Check for shorts, high resistance, or broken wires that may be causing the open circuit. | Multimeter |
Inspect the Reductant Tank Heater | Inspect the reductant tank heater itself to ensure that it is operational. If it has failed, it may need to be replaced to restore proper heating in the reductant tank. | Diagnostic Tool, Flashlight |
Repair or Replace Damaged Components | Repair any damaged wiring, connectors, or control units. If the heater or its control system is faulty, replace the necessary components to restore full functionality. | Wiring Repair Kit, Heater Replacement Kit |
Clear the Code and Test Drive | After completing repairs, clear the P202A code using an OBD-II scanner. Test drive the vehicle and monitor the heater system to ensure the issue has been resolved. | OBD-II Scanner, Vehicle Owner’s Manual |
Recheck for Codes | After the test drive, re-scan the vehicle to verify that the P202A code has not returned. | OBD-II Scanner |

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Hi, I am Juraj “Yuri” Lukacko. I got frustrated by unhelpful and scammy mechanics, so I decided to learn everything about car diagnostics myself. I test dozens of new car diagnostic tools every month along with learning new strategies to fix and customize cars. About Juraj Lukacko (Yuri)