The P20B3: Reductant Heater Coolant Control Valve Circuit Low fault code indicates that the circuit controlling the reductant heater coolant control valve is experiencing lower-than-expected voltage. This valve regulates coolant flow to the diesel exhaust fluid (DEF) heater, which is essential for maintaining the proper DEF temperature. Low voltage can impair the valve’s ability to function properly, leading to improper DEF heating and affecting emissions control. Common causes include low voltage in the circuit, a faulty valve, or a malfunctioning control module.
P20B3 – Quick Overview
| Code | Information |
|---|---|
| Meaning | P20B3: Reductant Heater Coolant Control Valve Circuit Low |
| Is it serious? | Yes, it can cause improper DEF heating, leading to emissions control problems and increased emissions. |
| Possible causes | – Low voltage in the heater coolant control valve circuit – Faulty valve – Faulty control module |
| How to diagnose? | – Measure voltage in the heater coolant control valve circuit – Test the valve – Check the control module functionality |
P20B3 Meaning
The P20B3 code signifies that the reductant heater coolant control valve circuit is receiving a lower voltage than expected. This valve controls the flow of coolant to the DEF heater to ensure the DEF is maintained at the right temperature. Low voltage in this circuit can prevent the valve from operating correctly, leading to insufficient heating of the DEF, which may impact emissions control.
Step-by-step diagnostic guide
| Action | Description | Tools Needed |
|---|---|---|
| Check for Other Codes | Use an OBD-II scanner to search for related fault codes that may provide additional context for the issue with the DEF heating system. | OBD-II Scanner |
| Measure Voltage in the Circuit | Use a multimeter to measure the voltage in the heater coolant control valve circuit and compare it with manufacturer specifications to confirm low voltage. | Multimeter |
| Test the Valve | Use a diagnostic tool to test the heater coolant control valve and ensure it is functioning correctly within the specified voltage range. Replace if necessary. | Multimeter, Diagnostic Tool |
| Check the Control Module Functionality | Inspect the control module responsible for managing the valve for any signs of malfunction or improper signal output to the valve. | Diagnostic Tool |
| Clear the Code and Test Drive | After repairs, clear the fault code using an OBD-II scanner and take the vehicle for a test drive to verify that the issue has been resolved. | OBD-II Scanner, Vehicle Owner’s Manual |
| Recheck for Codes | Re-scan the vehicle after the test drive to ensure the P20B3 code does not return. If the code reappears, further diagnostics may be required. | OBD-II Scanner |
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