The P20BB: Reductant Heater ‘A’ Control Circuit Low refers to a situation where the control circuit for the reductant heater ‘A’ is experiencing lower-than-expected voltage. This could point to issues in the electrical circuit, a faulty heater, or a problem with the control module.
P20BB – Quick Overview
Code | Information |
---|---|
Meaning | P20BB: Reductant Heater ‘A’ Control Circuit Low |
Is it serious? | Yes, this can cause the reductant system to malfunction, leading to improper emissions management. |
Possible causes | – Low voltage in the reductant heater ‘A’ control circuit – Faulty heater – Faulty control module |
How to diagnose? | – Measure voltage in the heater control circuit – Test reductant heater ‘A’ – Check the control module functionality |
P20BB Meaning
The P20BB fault code indicates that the control circuit for reductant heater ‘A’ is receiving insufficient voltage. This can affect the heater’s performance, which is crucial for the reductant system’s proper function in reducing emissions. Low voltage may be caused by wiring issues, a defective heater, or problems with the control module that governs the heater.
Step-by-step diagnostic guide
Action | Description | Tools Needed |
---|---|---|
Check for Other Codes | Use an OBD-II scanner to identify any other related codes that could help diagnose the issue. | OBD-II Scanner |
Measure Voltage in the Heater Control Circuit | Use a multimeter to measure the voltage in the control circuit for reductant heater ‘A’ and confirm it is within the specified range. | Multimeter |
Test Reductant Heater ‘A’ | Use a diagnostic tool to check the functionality of reductant heater ‘A’ and ensure it is working as expected. | Multimeter, Diagnostic Tool |
Inspect the Control Module | Verify the control module’s operation to ensure it is functioning properly and not causing the low voltage issue. | Diagnostic Tool |
Repair or Replace Wiring/Heater | If low voltage is detected, inspect wiring for shorts or disconnections and repair or replace reductant heater ‘A’ if necessary. | Wiring Kit, Replacement Heater |
Clear the Code and Test Drive | After making repairs, clear the code using an OBD-II scanner and test drive the vehicle to confirm that the issue is resolved. | OBD-II Scanner, Vehicle Manual |
Recheck for Codes | After the test drive, rescan the vehicle to ensure the P20BB code does not reappear. | OBD-II Scanner |

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