BMW DTC P20B8 – Reductant Metering Unit Heater Control Circuit High
DTC P20B8 meaning on BMW
DTC P20B8 on a BMW refers to a fault with the Reductant Metering Unit Heater Control Circuit High. This diagnostic trouble code indicates that the control circuit for the heater in the reductant metering unit is experiencing a high voltage condition, which can lead to improper operation of the system responsible for reducing harmful emissions.
BMW DTC P20B8 symptoms
Symptoms of DTC P20B8 on a BMW may include:
- Check Engine Light illuminated
- Reduced engine performance
- Increased fuel consumption
- Possible exhaust odor or smoke
BMW DTC P20B8 causes
Common causes of DTC P20B8 on a BMW include:
- Faulty reductant metering unit heater
- Short circuit or open circuit in the heater control circuit
- Corrosion or poor connections in the wiring harness
- Defective reductant heater control module
BMW DTC P20B8 seriousness
DTC P20B8 should be addressed promptly as it can lead to increased emissions and potential damage to the vehicle’s emissions control system. Ignoring this fault may result in the vehicle failing emissions tests and could lead to further engine issues if left unresolved.
How to diagnose DTC P20B8 on BMW
To diagnose DTC P20B8 on a BMW, a mechanic would typically perform the following steps:
- Use a diagnostic scanner to retrieve the fault code and related data
- Inspect the reductant metering unit heater and its control circuit for any visible damage or corrosion
- Check the wiring harness for continuity and proper connections
- Test the reductant heater control module for proper function
How to fix DTC P20B8 on BMW
To fix DTC P20B8 on a BMW, the following steps may be taken:
- Replace the faulty reductant metering unit heater if necessary
- Repair any short circuits or open circuits in the heater control circuit
- Clean or repair any corroded connections in the wiring harness
- Replace the defective reductant heater control module if needed
How to erase DTC P20B8 on BMW
To erase DTC P20B8 on a BMW, the fault code can be cleared using a diagnostic scanner that has the capability to reset codes. After the repair has been completed, the code can be cleared to reset the Check Engine Light and monitor the system for any recurring issues.
Recommended tools & DTC Scanners for BMW
Best Diagnostic App for modern BMWs: BimmerLink
Recommended Bluetooth adapter for Bimmerlink: OBDLink CX
Cable adapter for Bimmerlink: Enet Cable USB Type C
For older BMWs we recommend: Autel AutoLink AL319 (2024 version)
Easy-to-use Multimeter for reliable diagnostics: AstroAI Auto-ranging Multimeter
Some of the links on this page may be affiliate links, which means we may earn a small commission if you make a purchase. This helps us keep our DTC database up to date and provide valuable content for free. We only recommend products that we have tested and believe to be the best in their class.