Fix P20B4: STEP-BY-STEP diagnostic GUIDE!

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

CodeInformation
MeaningP20B4: 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

ActionDescriptionTools Needed
Check for Other CodesUse an OBD-II scanner to check for additional codes that may provide further insight into the issue.OBD-II Scanner
Measure VoltageMeasure the voltage in the heater coolant control valve circuit to ensure it is within manufacturer specs.Multimeter
Inspect the ValveTest the functionality of the heater coolant control valve to verify it is operating properly.Multimeter, Diagnostic Tool
Check the Control ModuleVerify the control module’s functionality to rule out a fault in the module.Diagnostic Tool
Inspect Wiring and ConnectionsInspect the wiring and connectors for any damage, shorts, or disconnections.Flashlight, Multimeter
Clear the Code and Test DriveAfter performing repairs, clear the code and test drive the vehicle to ensure the problem is resolved.OBD-II Scanner, Vehicle Manual
Recheck for CodesRescan the vehicle after the test drive to ensure the P20B4 code has not returned.OBD-II Scanner
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