The P20B4: Reductant Heater Coolant Control Valve Circuit High refers to a fault in the circuit of the reductant heater coolant control valve, indicating that the control valve is receiving a higher than expected voltage. This issue could be due to an electrical fault or a malfunction in the control module or valve itself.
P20B4 – Quick Overview
Code | Information |
---|---|
Meaning | P20B4: Reductant Heater Coolant Control Valve Circuit High |
Is it serious? | Yes, this issue can affect the vehicle’s emissions system, leading to reduced efficiency or improper functioning of the reductant heater. |
Possible causes | – High 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 |
P20B4 Meaning
The P20B4 fault code indicates that the control valve in the reductant heater coolant system is receiving a voltage that exceeds the normal range. This could be caused by an issue with the circuit, a malfunctioning valve, or a failure in the control module. This can disrupt the proper regulation of the coolant heater, which is critical for managing emissions.
Step-by-step diagnostic guide
Action | Description | Tools Needed |
---|---|---|
Check for Other Codes | Use an OBD-II scanner to check for additional codes that may provide further insight into the issue. | OBD-II Scanner |
Measure Voltage | Measure the voltage in the heater coolant control valve circuit to ensure it is within manufacturer specs. | Multimeter |
Inspect the Valve | Test the functionality of the heater coolant control valve to verify it is operating properly. | Multimeter, Diagnostic Tool |
Check the Control Module | Verify the control module’s functionality to rule out a fault in the module. | Diagnostic Tool |
Inspect Wiring and Connections | Inspect the wiring and connectors for any damage, shorts, or disconnections. | Flashlight, Multimeter |
Clear the Code and Test Drive | After performing repairs, clear the code and test drive the vehicle to ensure the problem is resolved. | OBD-II Scanner, Vehicle Manual |
Recheck for Codes | Rescan the vehicle after the test drive to ensure the P20B4 code has not returned. | OBD-II Scanner |

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