The P20B5: Reductant Metering Unit Heater Control Circuit/Open refers to a malfunction where the control circuit for the metering unit heater is open. This means the control circuit is not completing its path, which can lead to improper functioning of the heater. Potential causes include wiring issues, a faulty heater, or a malfunction in the control module.
P20B5 – Quick Overview
| Code | Information |
|---|---|
| Meaning | P20B5: Reductant Metering Unit Heater Control Circuit/Open |
| Is it serious? | Yes, this can prevent the reductant metering system from working properly, affecting emissions and engine performance. |
| Possible causes | – Open circuit in the metering unit heater control circuit – Faulty metering unit heater – Faulty control module |
| How to diagnose? | – Inspect the wiring for open circuits – Test the metering unit heater – Check the control module functionality |
P20B5 Meaning
The P20B5 fault code indicates that the control circuit for the reductant metering unit heater is open, meaning there is a break or disconnection in the circuit. This could prevent the heater from working correctly, which may impact the system’s ability to reduce harmful emissions, affecting overall vehicle performance.
Step-by-step diagnostic guide
| Action | Description | Tools Needed |
|---|---|---|
| Check for Other Codes | Use an OBD-II scanner to check for other related codes that may provide more context for the issue. | OBD-II Scanner |
| Inspect Wiring for Open Circuits | Visually inspect the wiring and connectors in the metering unit heater control circuit for any open circuits or disconnections. | Flashlight, Multimeter |
| Test the Metering Unit Heater | Test the metering unit heater using a diagnostic tool to verify if it is working within the proper range. | Multimeter, Diagnostic Tool |
| Check the Control Module | Verify the control module functionality to ensure it is not causing the open circuit. | Diagnostic Tool |
| Repair or Replace Wiring/Heater | If an open circuit is found, repair the wiring or replace the metering unit heater if necessary. | Wiring Kit, Replacement Heater |
| Clear the Code and Test Drive | After performing repairs, clear the code using the OBD-II scanner and test drive the vehicle to confirm the issue is resolved. | OBD-II Scanner, Vehicle Manual |
| Recheck for Codes | Rescan the vehicle after the test drive to ensure the P20B5 code has not returned. | OBD-II Scanner |
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