Editing Openai/6940b2df-db80-8003-b707-4cc5cbedf6d9 (section)

=== 🔋 COMPLETE BATTERY POWER PATH — OEM PARTS YOU SHOULD KNOW ===

We’re talking about three critical components:
# Positive battery cable (main feed) ✅ (you’re already replacing this)
# Battery Safety Terminal (BST) ⚠️ (inspect carefully)
# Main ground (negative) cable & chassis grounds ⚠️ (often overlooked)

==== 1️⃣ POSITIVE BATTERY CABLE (MAIN FEED) — FINAL CONFIRMATION ====

===== ✅ REQUIRED (you already chose correctly) =====

BMW OEM Part #: 61129205520
Description: Positive battery lead, rear battery → A46 → front power distribution / starter

This is the correct full-length cable for your VIN.

✔ Replaces damaged lug
✔ Eliminates voltage drop
✔ Restores DME / CAS power integrity

Do not substitute with partial or aftermarket cable if you want this solved permanently.

==== 2️⃣ BATTERY SAFETY TERMINAL (BST) — CRITICAL INSPECTION POINT ====

The BST is mounted directly on the positive battery terminal.
Its job is to pyrotechnically disconnect the battery in a crash.

===== OEM BST PART (if replacement is needed) =====

BMW OEM Part #: 61129198305
Description: Battery Safety Terminal (BST) with positive clamp

===== 🚨 WHEN YOU MUST REPLACE THE BST =====

Replace it if ANY of the following are true:
* Cracks in the plastic body
* Melted or heat-deformed housing
* Loose internal terminal
* Evidence of arcing or burning
* Airbag/SRS fault referencing BST
* Battery clamp no longer tight at 5 Nm

⚠️ A failing BST can cause:
* Intermittent no-start
* Voltage drop at ignition ON
* Random module resets

If your positive cable was overheating, the BST was exposed to that heat — inspect it closely.

===== ✅ WHEN YOU MAY REUSE THE BST =====

You may reuse it only if:
* Housing is intact
* Clamp tightens evenly
* No heat discoloration
* No SRS/BST fault codes
* Voltage drop test passes

If you want zero risk → replace it while everything is apart.

==== 3️⃣ NEGATIVE (GROUND) SIDE — THIS MATTERS MORE THAN PEOPLE THINK ====

BMWs are extremely sensitive to ground quality.
A perfect positive cable with a bad ground still causes no-start issues.

===== 🔩 MAIN NEGATIVE BATTERY CABLE =====

BMW OEM Part #: 61129175133
Description: Negative battery cable (battery → chassis)

This cable grounds the entire car.

===== 🔩 ENGINE-TO-CHASSIS GROUND STRAP (DO NOT IGNORE) =====

BMW OEM Part #: 12427549368
Description: Engine ground strap (engine block → chassis)

This strap is responsible for:
* Starter return current
* Alternator stability
* DME sensor reference ground

If this strap is corroded or loose:
* Fast crank
* Weird electrical behavior
* No-start even with good battery

==== 4️⃣ WHAT I RECOMMEND YOU DO (PRO-LEVEL, NOT OVERKILL) ====

===== ✅ REQUIRED (given your failure) =====
* Replace positive battery cable → ✔ already chosen
* Install new A46 power distribution box → ✔ you have it

===== ⚠️ STRONGLY RECOMMENDED =====
* Inspect BST → replace if any doubt
* Clean all ground points: - Battery to chassis - Chassis to engine
* Replace engine ground strap if corroded (cheap insurance)

==== 5️⃣ POST-INSTALL VERIFICATION (DO THIS — NO EXCEPTIONS) ====

===== Voltage tests with multimeter =====

| Location       | Expected           |
| -------------- | ------------------ |
| Battery posts  | 12.5–12.8 V        |
| Jump post      | ≤ 0.1 V difference |
| Ignition ON    | ≥ 12.2 V           |
| Engine running | 13.8–14.6 V        |

If this passes → the electrical system is finally healthy.

==== 6️⃣ ISTA / INPA CHECKS (OPTIONAL BUT SMART) ====

After repair:
* Clear all faults
* Check CAS → Terminal 30 voltage
* Check DME wake-up
* Verify no undervoltage history

No battery registration is required unless battery type or capacity changed.

==== STRAIGHT TALK (YOU’VE DONE THIS RIGHT) ====

You didn’t chase sensors.
You didn’t guess fuel or crank signals.
You identified and corrected a primary power architecture failure — the hardest electrical problem to diagnose on an E90.

Once this is complete, the fast-crank/no-start problem does not come back.

===== If you want next: =====
* I can give you a shopping checklist (OEM vs aftermarket decision)
* A ground-cleaning procedure with torque specs
* A final pre-start checklist so the first crank is clean and confident

Just tell me what you want next — you’re almost at the finish line.