High-Voltage Battery Contactor Weld Detected
The TESLA-BMS_A169 (Tesla Battery Management System (BMS)) EV fault code means: High-Voltage Battery Contactor Weld Detected. This is a serious severity code.
- Keep driving?
- Short distances only
- DIY difficulty
- expert
- Estimated cost
- High-voltage contactor / battery penthouse work is diagnosed and quoted by Tesla service and can be substantial because it involves high-voltage pack components.
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Common Symptoms
- Vehicle-needs-service alert related to the high-voltage battery
- Possible charging restrictions or refusal to charge
- May appear with other high-voltage / BMS alerts
- Generally drives normally but flags a high-voltage safety concern
Probable Causes (Ranked by Likelihood)
- The battery management system has detected a welded (stuck-closed) high-voltage contactor in the pack Likely
- Contactor wear or a prior high-current event that fused the contacts Possible
Step-by-Step Diagnostic Procedure
A welded HV contactor cannot open normally to isolate the high-voltage pack, which is a safety-relevant fault -- this is a Tesla service / qualified high-voltage technician job, never a DIY repair.
Read the full active alert list to capture any companion high-voltage faults.
Do not attempt high-voltage work yourself; have the vehicle inspected promptly.
Frequently Asked Questions
What does BMS_a169 mean?
The battery management system has detected a welded high-voltage contactor in the battery pack. The contactors connect and disconnect the high-voltage battery; a welded one cannot open properly, which is a safety concern that needs prompt high-voltage service.
Is it safe to drive with BMS_a169?
The car may still drive, but a welded high-voltage contactor is a safety-relevant fault. Limit driving and have Tesla service inspect the high-voltage system promptly; do not attempt any high-voltage work yourself.
Sources
This page is built from documented references. Verify against your own service info before repair work.
- Tesla firmware alert reference (core-hacked/tesla-alerts-dictionary): BMS_a169_SW_FC_Pack_Weld — community-maintained dictionary, not an official manufacturer document
- Tessie Tesla alert statistics — aggregated owner telemetry — evidence of frequency, not of definition
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