The P20B7: Reductant Metering Unit Heater Control Circuit Low refers to a low voltage condition in the control circuit of the metering unit heater. This may indicate an issue with the heater’s electrical supply, potentially caused by wiring problems, a faulty heater, or a malfunction in the control module.
P20B7 – Quick Overview
| Code | Information |
|---|---|
| Meaning | P20B7: Reductant Metering Unit Heater Control Circuit Low |
| Is it serious? | Yes, this issue can prevent the reductant system from operating properly, which could lead to higher emissions. |
| Possible causes | – Low voltage in the metering unit heater control circuit – Faulty heater – Faulty control module |
| How to diagnose? | – Measure voltage in the heater control circuit – Test the metering unit heater – Check the control module functionality |
P20B7 Meaning
The P20B7 fault code indicates that the voltage in the control circuit of the reductant metering unit heater is lower than expected. This low voltage condition can impact the heater’s performance, potentially leading to problems with emissions management. Common causes include wiring issues, a failing heater, or a malfunction in the control module responsible for controlling the heater.
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 give more insight into the issue. | OBD-II Scanner |
| Measure Voltage in the Heater Control Circuit | Use a multimeter to measure the voltage in the metering unit heater control circuit and ensure it is within the specified range. | Multimeter |
| Test the Metering Unit Heater | Use a diagnostic tool to test the heater’s functionality and check if it is operating within manufacturer specifications. | Diagnostic Tool, Multimeter |
| Inspect the Control Module | Verify the control module’s performance to ensure it is not causing the low voltage issue. | Diagnostic Tool |
| Repair or Replace Wiring/Heater | If the voltage is low, inspect the wiring for shorts or disconnections, and repair or replace the heater as needed. | Wiring Kit, Replacement Heater |
| Clear the Code and Test Drive | After making repairs, clear the code using the OBD-II scanner and take the vehicle for a test drive to verify the problem is fixed. | OBD-II Scanner, Vehicle Manual |
| Recheck for Codes | After the test drive, rescan the vehicle to ensure the P20B7 code does not return. | OBD-II Scanner |
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