BMW DTC P164B – Main Relay Overvoltage
DTC P164B meaning on BMW
DTC P164B on a BMW indicates a Main Relay Overvoltage fault. This fault code is triggered when the Engine Control Module (ECM) detects that the voltage supplied to the main relay exceeds the specified limit.
BMW DTC P164B symptoms
Symptoms of a DTC P164B on a BMW may include:
- Check Engine Light (MIL) illuminated
- Engine may not start or may have difficulty starting
- Electrical issues such as erratic behavior of lights or accessories
BMW DTC P164B causes
Common causes of a DTC P164B on a BMW include:
- Main relay failure
- Short circuit in the main relay circuit
- Faulty wiring or connections in the main relay circuit
- Issues with the ECM
BMW DTC P164B seriousness
The seriousness of a DTC P164B on a BMW depends on the underlying cause. Ignoring this fault can lead to starting issues or potential damage to other electrical components in the vehicle. It is recommended to address this issue promptly.
How to diagnose DTC P164B on BMW
To diagnose a DTC P164B 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 main relay and its connections for any visible damage
- Check the voltage supply to the main relay to ensure it is within specifications
- Perform a thorough inspection of the main relay circuit for any shorts or open circuits
How to fix DTC P164B on BMW
To fix a DTC P164B on a BMW, the following steps may be taken:
- Replace the main relay if it is found to be faulty
- Repair any damaged wiring or connections in the main relay circuit
- If the ECM is suspected to be the issue, it may need to be reprogrammed or replaced
How to erase DTC P164B on BMW
To erase a DTC P164B on a BMW, the fault code can be cleared using a diagnostic scanner. After the repair has been made, the code can be cleared to reset the Check Engine Light and ensure that the issue 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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