2015 Model S 85D Pack Repair

SMT Pack Summary (June 17–23, 2026)

Module Voltage Map (SMT Spreads)

Green = flat (<10 mV) • Orange = elevated • Red = high priority

Full Module Table

TBMM Progress — 3 of 16

SMT vs TBMM Comparison

Physical Inspection (Sensor Leads & BMS Board)

Confirmation of visual/physical inspection for sensor leads and the BMS circuit board on each module. Update as modules are opened or inspected.

Balancing (TBMM)

The TBMM (Electric Avenue) supports automatic active balancing of modules outside the pack. Good candidate for Module 16 (confirmed 146 mV real imbalance).

How to choose the balance point

The balance point is the target voltage the TBMM balances the cell groups toward.

For Module 16 (current range ~3.681 V low to 3.827 V high):

• 3.750 V — roughly the middle of the current spread
• 3.720–3.740 V — slightly more conservative (pulls the high groups down more)

General approach:

• Look at the live cell-group voltages on the TBMM.
• Pick a voltage below the highest groups and near or above the lowest ones.
• Stay comfortably inside the normal range for these modules (roughly 3.6–4.0 V).
• Set it in the web interface, turn balancing on, and monitor. You can adjust the point later if progress stalls.

After balancing, recheck the imbalance. Goal is ≤ 6 mV to match the pass criteria.

Log balancing sessions and post-balance results here as they are done.

Pass Criteria

Cell group imbalance ≤ 6 mV = PASS. High ≤ 4.20 V, low ≥ 3.00 V.

Fault Summary

Peak at acquisition: 22 codes. After Toolbox (June 20): cleared to 4 remaining.

Root Cause

Primary: Pyro fuse cover (1020227-00-C) gasket failure → water entry. Confirmed water + corrosion in cavity.

Pyro fuse identified: ASY,FUSE,HVBAT,HI DURA,83 • TPN 1053124-00-A • TSN T15E0022094.

Contributing: deep discharge, 12V failure, charge port door swap without relearn, BMB connector corrosion.

What “Connector Issue” Means

On Module 12 the site notes a connector issue because the large voltage spread reported by Scan My Tesla disappeared when the module was measured directly with the TBMM.

• SMT (June 2026): Module 12 showed an 81 mV spread.
• TBMM (direct test): Same module measured only 4 mV imbalance and PASSed. Cell groups were tightly matched.

The cells themselves were healthy. The BMS was simply reading them incorrectly through the connector / sense-lead path. This is a false or inflated reading, not real cell imbalance.

Why This Happens

The BMS reads cell-group voltages through sense leads and BMB (Battery Management Board) connectors. Anything that adds resistance or corrosion in that path can make the BMS report a fake spread even when the cells are fine.

Common causes on these packs:

• Water intrusion (confirmed in the pyro-fuse cavity on this pack)
• Corrosion on connector pins or sense wires
• Loose or high-resistance contacts
• Damaged or oxidized sense leads
• BMB board issues that affect voltage sensing (related to BMS_a129)

Module 14 showed the same pattern (low true imbalance on TBMM). Module 16 is the opposite: its 146 mV TBMM result confirmed a real cell-group imbalance.

SMT vs TBMM

• SMT reads through the vehicle’s BMS and the full connector chain. It can show inflated spreads if connectors or sense wiring are bad.
• TBMM connects more directly to the module and measures the actual cell groups. A big drop from SMT spread to TBMM spread is strong evidence of a connector/sense problem rather than cell degradation.

Healthy modules typically show ≤ 6 mV imbalance on TBMM. Anything significantly higher is treated as a real issue until proven otherwise.

Next Diagnostic Steps

For modules that show a connector-style pattern (high SMT, low TBMM):

• Inspect and reseat the BMB connector
• Check sensor leads for corrosion, damage, or high resistance
• Visually inspect the BMS circuit board for corrosion or damage
• Clean contacts and retest

The Physical Inspection table in the TBMM tab is ready to log those results as modules are opened.

Repair Timeline

Related Project Pages

Other sites on 5udyk.com tied to this 85D pack repair and Tesla work.