Reductant Tank Heater Control Circuit Low
The P202B code indicates that the powertrain control module (PCM) has detected a low voltage condition in the reductant (DEF) tank heater control circuit. This heater is used to prevent diesel exhaust fluid from freezing in cold temperatures. A low circuit condition typically means the voltage is below the expected threshold, often due to a short to ground, faulty heater element, or damaged wiring/connectors.
01. Most Common Causes
- Short to ground in the heater control circuit
- Faulty reductant tank heater element
- Damaged wiring or connectors in the heater circuit
- Corroded or loose electrical connections
02. Symptoms You Will Notice
- Illuminated check engine light
- Reduced fuel economy or performance in cold weather
- Possible DEF system warning messages on the dashboard
- Increased emissions due to improper DEF dosing
03. Step-by-Step Diagnosis
Step 1: Use a scan tool to retrieve all stored codes and freeze frame data.
Step 2: Visually inspect the reductant tank heater wiring and connectors for damage, corrosion, or loose connections.
Step 3: Measure the resistance of the heater element with a multimeter; compare to manufacturer specifications.
Step 4: Check for voltage at the heater connector with the ignition on; if voltage is low, trace the circuit for shorts or opens.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is generally safe to drive short distances, but prolonged driving with a faulty DEF heater can lead to DEF freezing in cold weather, causing poor emissions performance and potential damage to the SCR system. It is recommended to repair promptly.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for diagnosis and repair, depending on whether the issue is a simple wiring fix or requires replacement of the heater element or tank assembly.