5th Gen high-output alternator swap, now cranks/won’t start

Hello fellow 4Runner’ers,

Got myself in a bit of a pickle… So I’m installing a ~10,000 watt audio system along with a winch and some other standard battery draining fare. My first step was to install a high-output alternator. I ordered a 250 amp fluorescent green alternator from JS Alternators. I swapped my old one out for it (fairly straightforward, uneventful install) and I press the button when I finish and all I get is “crank, crank, crank…” for 10 seconds - not even a sliver of an attempt to want to start, just the same monotonous crank over and over again… It’s been three days now and I still can’t pinpoint the cause…. I’ve checked my battery(s), all my connections, my leads, my grounds and still just, “crank, crank, crank…”,

Worth mentioning, I began to strip the truck down in preparation for the audio install and I was installing a lo-pro number w/ a winch and electric fold out steps as well so the truck currently has no seats, no trim, no a/v center, no door panels, no bumper, no raptor lights, etc.,etc….

Could there be some sort of fuel cut-off/inertia type switch I could have triggered while stripping the car down?

Thanks in advance for your input everyone. I just want to hear the sweet sound of that Overland series exhaust again!

 

Welcome

 

I’ve had similar problems. My fix was a fuse in the engine compartment. It was the 10a injector fuse.

 

Welcome. This is quite the first post! 10K watt sound is going to be wild! I definitely want some details on that part.

do you have an ODB2 scanner of any type to pull codes?

a brief chat with a LLM (AI)

5th gen 4Runner fuel system

• No manual inertia switch: The 5th generation 4Runner does not have a manual, inertia-type fuel pump cut-off switch for normal operation. Its system is managed electronically.
• Electronic control: The vehicle's computer controls the fuel pump based on various sensor inputs, and there is no external switch to manually reset in the event of a crash.

disconnect battery for 10 minutes; then reconnect
check ALL fuses (especially the INJ fuse)
replace battery in both key fobs

this thread:
https://www.4runners.com/threads/4runner-has-power-but-no-crank.39354/
talks about an ECU fault

this thread:
https://old.reddit.com/r/4Runner/comments/qhs3or/comment/hifdyys/
Emergency start function (vehicles with a smart key system) When the engine does not start, the following steps can be used as an interim measure to start the engine if the engine switch is functioning normally: 1 Set the parking brake. 2 Shift the shift lever to P. 3 Turn the engine switch to ACCESSORY mode. 4 Press and hold the engine switch for about 15 seconds while depressing the brake pedal firmly.

hopefully you will stick around and let us know what solves your problem AND posts about the soon to be awesome audio install.

 

@Oscar thank you so much for your thorough reply!

yes, yes i do have a scanner and i’m worried that what it’s saying might be true: the ECM. i couldn’t possibly reflash this myself could i? is there such a thing as performance ECM’s that i could buy preprogrammed? trying to avoid a trip to the (st)dealer. also is an ecm same as an ecu? and - if it is fried, what would’ve caused that?

 

the B1206 & B2321 are gonna be a bad time and will definitely cause headaches.

ECU

AI said:
"An ECU (Engine Control Unit) for a Toyota is the "brain" of the engine that monitors and controls various functions for optimal performance and fuel efficiency"

ECM

AI said:
An ECM for a Toyota is an Engine Control Module, the vehicle's computer that manages critical functions like fuel injection, ignition timing, and emissions control

https://www.ancel.com/blogs/news/ecu-vs-ecm-explaining-the-differences
https://www.borstautomotive.com/whats-the-difference-between-an-ecu-ecm-tcm-and-pcm/
https://rpmautocenter.com/are-the-ecu-and-the-ecm-the-same/

TLDR; same / same

can you reflash it (ECU/ECM) yourself? most likely not.
are their options out there? yes

https://www.4runners.com/threads/2020-2024-tuning.37717/
https://www.lethalperformance.com/v...4runner-dual-vvt-i-270hp-vrt-toy-4rn-270.html
https://overlandtailor.com/ott-5th-generation-toyota-4runner-custom-tuning/
https://tuningtechfs.com/toyota-4runner-ecu-tune/

can you buy one (ECM/ECU) ready to go? yes
https://www.fs1inc.com/2020-toyota-...ne-computer-ecm-ecu-programmed-plug-play.html

I'm not sure how plug/play used ones are.. but they are out there
https://www.ebay.com/itm/335177442240
(my guess is it simply will not 'just work' as the VIN needs to match other pieces of the puzzle)

I'm still trying to wrap my head around HOW swapping the alternator caused this issue. Bad alternator kinda is the answer IF nothing else went wrong (ground short, bad wiring, etc..)

JS Alternator is a well regarded brand, BUT their warranty
https://js-alternators.com/pages/warranty

"This warranty does not cover other parts or equipment on the vehicle and it does not cover labor expenses related to the removal or installation of the alternator,"

I would at a minimum take the alternator out and take it to a local alternator rebuild shop, they should be able to test or otherwise verify proper operation.

 

Welcome

 

Check your ECU B fuse. I had a no start after fiddling with some electrical stuff and went down the rabbit hole of replacing modules just to find out it was one stupid little fuse that simultaneously saved the day and caused a huge headache. Similar codes. I did not note them as the fuse replacement fixed it but the descriptions are familiar

 

The 4runner electrical system is the most complex system on the vehicle.

When you mess with it without enough knowledge you do so at your peril...

 

Its crazy how simple yet sensitive it is to things it does not like, like aftermarket everything. Had hurtles with my Remote start and full sound system upgrade. Took about 2 years to get it all worked out. lol