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

=== Assistant: Good — these photos tell the story very clearly. ===
Good — these photos tell the story very clearly. I’m going to do two things below, cleanly and methodically:
# Confirm what we’re seeing in your photos (what’s wrong and what’s been altered)
# Give you strict, step-by-step replacement instructions for the rear power distribution box (A46) exactly as the BMW manual intends — but tailored to the condition of ''your'' car, not a showroom example.

No fluff. No guessing.

==== From your images, here is what is objectively visible: ====

===== - The plastic housing is distorted and heat-aged =====
* The aluminum fuse carrier plate shows oxidation and heat staining
* At least one high-current connection shows darkened metal, which equals resistance

On BMWs, any heat at these junctions = voltage loss under load, even if the starter still spins.

===== I can clearly see: =====
* Thin blue, green, white, and red wires
* These are NOT BMW OE battery cables
* They are routed across high-current studs and the BST area

This is critical:

: 

These wires must not be transferred to the new panel unless you know exactly what they feed.

===== The rust and residue in the battery tray confirms: =====
* Moisture has been present
* Moisture + high current = accelerated corrosion
* This absolutely contributes to distribution panel failure

So yes — replacing A46 is justified and necessary.

==== (Manual-correct sequence, adapted to your exact setup) ====

This is written so you can print it and follow it in the trunk.

==== - 10 mm socket (battery terminals) ====
* 13 mm socket (distribution studs)
* Ratchet + extension
* Torque wrench (important)
* Marker or masking tape (labeling)
* Camera/phone (mandatory)

==== 1. Key OUT of ignition ====
# Trunk open
# All doors closed (or latch the trunk striker with a screwdriver)

: 

==== 1. Remove the right-side trunk trim panel ====
# Remove the battery hold-down bracket
# You should now fully see: - Battery - Rear power distribution box (on top) - IBS on the negative cable

==== ### ====
# Loosen the negative terminal clamp
# Carefully lift it off
# Lay it aside without stressing the IBS

⚠️ Do not twist, pry, or let the IBS hang by the wire

===== 1. Open the red BST cover =====
# Loosen the positive terminal clamp
# Lift it off and secure it so it cannot touch metal

==== 1. Remove the battery hold-down bolt ====
# Disconnect the battery vent hose
# Lift the battery out (it’s heavy — lift straight up)

Now the A46 panel is free and accessible.

==== This is the critical part. ====

===== Before loosening anything: =====
* Take clear photos
* Label each cable with tape: - “Starter / Jump Post” - “Front Junction” - “DME / Vehicle Feed” - Anything aftermarket — label it “NON-OEM”

===== 1. Using a 13 mm socket, remove one stud nut at a time =====
# Remove one cable at a time
# Do NOT stack cables loosely — keep each grouped

⚠️ The metal fuse links inside A46 are not replaceable
This is why the whole unit must be swapped.

==== Before installing the replacement A46: ====

===== - No blueing =====
* No pitting
* No melted insulation

If any cable end is heat-damaged:

: 

==== 1. Place the new A46 onto the battery location ====
# Transfer OEM cables only, one at a time, to matching studs
# Torque each stud nut to 15 Nm (11 ft-lb)

⚠️ Do NOT overtighten — aluminum studs will strip.

===== Those small gauge wires: =====
* Do not belong on A46
* Must be traced before reconnecting
* If they powered an accessory, they should be fused elsewhere

Do not blindly reinstall them.

==== 1. Set battery back in tray ====
# Reconnect vent hose
# Install hold-down clamp

==== 1. Positive terminal FIRST ====
# Torque to 5 Nm (44 in-lb) if M6
# Negative terminal LAST
# Ensure IBS is seated and not twisted

==== With a multimeter: ====
* Battery posts: 12.5–12.8 V
* Jump post: within 0.1 V of battery

If there’s more difference than that — stop and recheck connections.

==== If the battery was replaced or type changed: ====
* ISTA → Vehicle management → Battery replacement → Register

==== Based on your photos: ====
* The A46 needed to be replaced
* There has been heat + moisture + non-OEM wiring
* This absolutely can cause low system voltage and no-start, even with fast cranking

You’re on the right repair path.

===== - Identify each stud on your A46 by function =====
* Help you trace the mystery wires
* Walk you through ISTA checks after installation
* Or verify DME power integrity step-by-step

Add the remaining photos when ready — I’ll stay with you through this until it’s right.