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

=== Assistant: Here’s the straight story: on an E90, you can absolutely get a “cranks fast but won’t start” situation if the rear powe… ===
Here’s the straight story: on an E90, you can absolutely get a “cranks fast but won’t start” situation if the rear power distribution panel on top of the battery (A46) is heat-damaged internally—because it doesn’t just feed the starter cable. It also feeds engine electronics (DME/Valvetronic) on a separate path. The manual even calls out two different power feeds leaving the battery area—one to the jump post/starter/alternator and another to engine electronics. 461232-BMW_3-Series_E90-E91_200…

 461232-BMW_3-Series_E90-E91_200…

==== BMW calls it the Rear power distribution panel (high amperage fuses) (A46) and it sits directly on top of the battery in the trunk. 461232-BMW_3-Series_E90-E91_200… ====

Those “big fuses” inside it are fusible links and are not replaceable separately—so if the panel is melted/warped, replacement as an assembly is the right move. 461232-BMW_3-Series_E90-E91_200…

It has outputs/lines going to: starter/alternator/jump post, engine electronics, IBS electronics, and the junction box. 461232-BMW_3-Series_E90-E91_200…

==== I’m going to call this out because it matters: ====
* If you meant 11.4 VOLTS while cranking, that’s actually strong (most cars dip closer to ~9.6–10.5V during crank, depending on temperature/load). So your problem may be not battery strength but fuel/spark/DME power/immobilizer.
* If you meant 11.4 AMPS, that’s not a realistic cranking number—starters pull hundreds of amps. That would mean the reading is being interpreted wrong or measured in the wrong mode.

The PB6000 tests below will clear that fog fast.

==== This is the exact removal flow the manual gives, and it’s the safest way to access A46. 461232-BMW_3-Series_E90-E91_200… ====

===== - 10mm socket/wrench (battery terminals) =====
* Ratchet + extensions
* Torque wrench (important)
* Gloves/eye protection
* Phone to take “before” photos (do it—future you will thank you)

===== 1. Ignition OFF. 461232-BMW_3-Series_E90-E91_200… =====
# In trunk, open the battery compartment. Remove right-side trim (plastic retainer). 461232-BMW_3-Series_E90-E91_200…
# Remove the protective bracket over the battery (mounting fasteners) and lift it off. 461232-BMW_3-Series_E90-E91_200…
# At the battery, disconnect negative FIRST (loosen fastener “A”). 461232-BMW_3-Series_E90-E91_200… - Be gentle: the IBS is attached to the ground cable and is stress-sensitive. The manual is loud about not pulling, prying, or levering on the IBS/ground cable. 461232-BMW_3-Series_E90-E91_200…
# Unlock the BST plastic cover, loosen the positive cable fastener “B.” 461232-BMW_3-Series_E90-E91_200…
# Carefully lift the rear power distribution panel (A46), positive cable, negative cable, and IBS off the battery and lay aside. 461232-BMW_3-Series_E90-E91_200…
# Remove battery hold-down bolt “C,” disconnect the vent hose, lift the battery out. 461232-BMW_3-Series_E90-E91_200…

===== Bentley shows you how to lift A46 off as an assembly. Once it’s off and on a bench: =====
# Photograph everything: every cable routing, every nut, every connector position.
# Transfer cables/connectors from the old A46 to the new A46 one at a time (so nothing gets swapped). - Remember: A46 includes the high-amperage fusible links—they aren’t serviced separately. 461232-BMW_3-Series_E90-E91_200…
# Inspect the mating points for heat damage (discoloration, pitting, looseness). Any heat at a high-current joint = resistance = voltage drop = future meltdown.

===== - Reconnect negative LAST when reinstalling the battery. 461232-BMW_3-Series_E90-E91_200… =====
* Battery post pinch-bolt torque specs: - M6 = 5 Nm (44 in-lb) - M8 = 15 Nm (11 ft-lb) 461232-BMW_3-Series_E90-E91_200…
* After battery reconnect, if the battery was replaced/changed in rating: the car may need CAS recoding + battery registration. 461232-BMW_3-Series_E90-E91_200…

==== Most PB-style testers follow this same logic. If your menu wording differs, the flow is still identical. ====

===== 1. Clamp PB6000 leads directly to the battery posts (not the cable ends), or to the underhood jump post + a solid engine ground. =====
# Select Battery Test → In Vehicle
# Choose battery type (Flooded / AGM / etc.)
# Enter the battery rating shown on the label (usually CCA).
# Run test and note: - Voltage - State of Health (SOH) - Internal resistance - “Good / Recharge / Replace” verdict

What you’re looking for: a battery can show “charged” but still be weak under load (high internal resistance). The tester catches that.

===== 1. Select Cranking Test / Starting Test =====
# Crank the engine (even if it won’t start).
# Record minimum voltage during crank.

Interpretation cheat code:
* Low min voltage and “slow crank” → weak battery / bad starter / engine drag
* Low min voltage and “fast crank” → usually measurement point issue or bad connection/voltage drop
* Healthy min voltage (your claimed 11.4V) and no start → stop blaming the battery and chase DME power, fuel, spark, CAS start authorization

===== Once it starts and idles: =====
* PB6000 Alternator Test at idle and with loads on.
* Bentley’s charging quick-check numbers: ~12.6V key off and 13.5–14.5V running; and with loads at ~2000 rpm it should stay above 12.6V. 461232-BMW_3-Series_E90-E91_200…

==== This is the fastest “truth serum” for high-current problems. ====

===== - Put multimeter red lead on battery + post (in trunk). =====
* Put multimeter black lead on underhood jump post.
* Crank engine.
* Reading should be very low (ideally under ~0.2V). Higher = resistance in A46/cable/junctions.

===== - Red lead on battery – post. =====
* Black lead on a bare metal point on engine block.
* Crank engine.
* Should also be low (ideally under ~0.2V). Higher = bad ground path (chassis ground, engine ground strap, IBS connection issues).

If either test is high, that’s where your “melted, warped, flimsy” story turns into a measurable cause.

==== Bentley stresses that clean, consistent voltage matters—especially when coding/programming—and recommends a power supply style approach. 461232-BMW_3-Series_E90-E91_200… ====
* Connect charger/power supply to engine compartment B+ and ground (jump post + ground), and follow the charger’s voltage setting instructions. 461232-BMW_3-Series_E90-E91_200…
* Bentley mentions BMW’s charging voltage recommendation 14.8V and warns don’t exceed 16.5V. 461232-BMW_3-Series_E90-E91_200…  461232-BMW_3-Series_E90-E91_200…

For diagnostics (ISTA/INPA), set the charger to a stable supply mode if it has one (commonly ~13.6–14.4V). For programming (ISTA-P), you want maximum stability—no bargain “dumb charger” behavior.

==== Your symptom screams: either DME isn’t powered/awake or it’s awake but you’re missing fuel/spark or start authorization. ====

===== 1. Put the charger on the jump post + ground (stable voltage). =====
# Plug in K+DCAN, ignition ON (cluster lit).
# Open ISTA → Operations → Read out vehicle data → Complete identification
# Run Vehicle Test.
# Look at the control unit tree: - If DME is not responding, that’s a giant arrow toward A46 / fusible link / DME power feed (because the starter can still crank on its own feed).
# Pull fault memory for DME + CAS.
# Run the guided test plan for engine does not start (ISTA will walk you through rpm while cranking, start enable, etc.).

===== 1. Open INPA, choose E90 chassis. =====
# Go into CAS: - Look for start enable / terminal 50 request / key recognized style statuses.
# Go into DME (MSV/MSD for N52): - Confirm you can communicate - Watch live data while cranking: RPM signal (if 0 rpm, crank sensor/rpm input problem) - Check any “start conditions not met” flags

===== ISTA-P is for programming/coding. Don’t bring it out until: =====
* the car starts reliably, and
* you have stable power supply voltage (programming on shaky voltage is how modules get bricked).

==== 1. Replace the melted A46 (your panel is already physically telling on itself). Use the Bentley battery removal steps above. 461232-BMW_3-Series_E90-E91_200… ====
# Do voltage-drop Test 1 and Test 2 during cranking (before and after).
# Run ISTA Vehicle Test and see if DME is alive.
# If DME is alive: chase fuel/spark/start authorization instead of charging parts blindly.

If you want, tell me one detail and I’ll tailor the no-start path precisely: When you crank, does the tach needle move even a little? (That single sign often separates “DME has rpm signal” from “no rpm signal,” and it changes the whole hunt.)