BMW DTC U1821 – Drive Motor ‘A’ Control Module Lost Communication With Diagnosis OBD Hybrid via FlexRay
DTC U1821 meaning on BMW
DTC U1821 on a BMW indicates that the Drive Motor ‘A’ Control Module has lost communication with the Diagnosis OBD Hybrid via FlexRay. This means that there is a communication issue between the control module and the diagnostic system, which can affect the proper functioning of the drive motor.
BMW DTC U1821 symptoms
Symptoms of DTC U1821 on a BMW may include:
- Check Engine Light illuminated
- Loss of power or performance
- Difficulty starting the vehicle
- Transmission shifting issues
BMW DTC U1821 causes
Possible causes of DTC U1821 on a BMW include:
- Faulty Drive Motor ‘A’ Control Module
- Wiring or connection issues between the control module and the diagnostic system
- Software or programming errors
BMW DTC U1821 seriousness
The seriousness of DTC U1821 on a BMW depends on the underlying cause. Ignoring this fault can lead to further damage to the drive motor or other related components. It is recommended to address this issue promptly to prevent potential safety hazards or costly repairs.
How to diagnose DTC U1821 on BMW
To diagnose DTC U1821 on a BMW, you can follow these steps:
- Use a diagnostic scan tool to retrieve the fault codes from the vehicle’s computer.
- Inspect the wiring and connections between the Drive Motor ‘A’ Control Module and the diagnostic system for any visible damage or loose connections.
- Perform a communication test to check for proper data exchange between the control module and the diagnostic system.
How to fix DTC U1821 on BMW
To fix DTC U1821 on a BMW, you can try the following:
- Inspect and repair any damaged wiring or connections between the control module and the diagnostic system.
- If the Drive Motor ‘A’ Control Module is faulty, replace it with a new one.
- Update the software or programming of the control module if necessary.
How to erase DTC U1821 on BMW
To erase DTC U1821 on a BMW, you can use a diagnostic scan tool to clear the fault codes stored in the vehicle’s computer. After addressing the underlying issue and fixing the root cause, you can then reset the codes to see if the problem has been resolved.
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
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