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Old 01-17-2025, 03:22 PM #16
Dave4RCR Dave4RCR is offline
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Quote:
Originally Posted by drallan View Post
Thanks,

I'm just trying to figure out where to take that reading from. All of my readings have been during idle, but I'm not sure where to take the reading.

I thought the big red positive cable at the battery was connected to the alternator, so I've been touching some exposed wire on the positive cable (not just battery post) and a good ground on the engine and getting mid-high 13v. While driving the light never goes off.

I know the alternator should be around low 14s, so maybe the mid 13s is low enough to trip the light and the alternator is just failing, but strong enough to keep the battery charged for now.

Just wish I could find out where the OBDII got the voltage I'm seeing on Torque and why it differs from what I see when I put the volt meter on the battery.

Does the OBDII reading measure a regulated 12v (TBH I never checked until this occurred so it could have always been down). What do others see when checking voltage on Torque?


Does anyone know what voltage trips the "battery" light on the dash? Is it below 14? I could be wrong in my assumptions.
I read in a post that you can get the volt measure from the alternator by connecting the multimeter to the alternador post. It’s easily accessed you just need to remove the plastic cap.

Now. If you follow the Alt-S fuse in the engine bay, there are 3 wires that connects to a plug just below the alternator post. I believe the PIN4 is the one that goes to the computer.

See attached
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Where does ECU get system voltage?-img_2821-jpg 
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Old 01-20-2025, 02:13 PM #17
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Quote:
Originally Posted by 88Center View Post
Electrical Diagrams for 4th gen 4Runner

Relay locations
Electric wiring routing
Power Source
Engine Control for 1GR–FE
Engine Control for 2UZ–FE
I was never able to get the last 2 uploads to download / open properly.
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Old 01-20-2025, 02:52 PM #18
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Quote:
Originally Posted by drallan View Post
I was never able to get the last 2 uploads to download / open properly.
Let's try a diff way

I have the entire manual in PDFs, if I knew where to upload entire manual, I would.

https://imgur.com/l4oaZ4D
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File Type: pdf em03m5-1.pdf (131.5 KB, 10 views)
File Type: pdf em03m4-2.pdf (145.8 KB, 10 views)
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Old 01-20-2025, 04:48 PM #19
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Thank you, that worked!
Had some super cold weather hear in Maryland and I don't have a garage so it has been slow going. Good news is runner has been working, got a different OBD reader (non-Bluetooth) and it is showing same voltage as I'm reading with the multi-meter, Mid-13s+. On top of that, tested my other Bluetooth adapter in a different vehicle and it was constantly showing a volt lower than expected, so for some reason that adapter is off. It was an inexpensive Amazon find and probably ran its course. So, good news is, I'm now showing consistent readings.

But, I'm still not sure why I'm getting the battery light as I feel 13.6+ should be plenty. Understand it might be a little low, but alternator isn't that old, and battery is less than a year old. I've cleaned every connection and ground I can find. Have disconnected, cleaned and reconnected the alternator plug and cable, as well as checked all the fuses. Only one I can't really get to is the starter ground for obvious reasons. Did even take it to the carwash and gave engine bay a decent light spray. I do have some minor valve cover leaks, but nothing has changed. Next step when I get a chance is to change out the battery terminals, they are snug, but pretty much maxed out and deformed.

Maybe when it warms up one of these days I'll do the big 3 upgrade (if I ever get this solved). Any write ups on that? I've found some for the 3rd Gen and other Gens, but not the 4th.

For those who have changed out battery cable terminals, what did you use / how did you do it? Not much slack, especially on the negative end. Afraid to cut / remove too much or even pry off old terminal and not have enough slack to attach new terminal end. Any recommended brands to go with others have used? A lot of the local auto part store ones don't look any better than what I have on there now.

Is there any way to just shim the battery post itself a bit to make the connection tighter? Just don't want to be mixing metals. WOuld be nice to isolate the problem before I start cutting cables and potentially make it worse.
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Old 01-20-2025, 05:35 PM #20
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Quote:
Originally Posted by 88Center View Post
Let's try a diff way

I have the entire manual in PDFs, if I knew where to upload entire manual, I would.

https://imgur.com/l4oaZ4D
That worked for me as well, thanks!
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Old 01-21-2025, 11:39 AM #21
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From the FSM for 1GR-FE
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Where does ECU get system voltage?-screenshot-2025-01-21-9-38-26-am-jpg 
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Old 01-21-2025, 04:33 PM #22
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Quote:
Originally Posted by Runnin on E View Post
From the FSM for 1GR-FE
You know what, I never considered that the alternator wasn't producing the correct current, just assumed that if the voltage was good the alternator was good. But checking the amps its putting out is a good idea. That could be the issue.

Thanks for the suggestion.

I don't have a designated ammeter, assuming a standard household multimeter should work? I've got a few so I could set it up like the FSM suggests (with a spare set of hands or 2) to measure voltage and amp output.

Depending on how long my cables are I might disconnect the big cable (cable B) off the alternator, I think it has a ring terminal, and use alligator clips on the multi-meter to clip onto the post of alternator w/ one and ring on the other to complete the circuit. Or I can run out and grab some fresh cable and make up a new one to run it to the battery.
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Old 01-21-2025, 04:47 PM #23
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Quote:
Originally Posted by drallan View Post
You know what, I never considered that the alternator wasn't producing the correct current, just assumed that if the voltage was good the alternator was good. But checking the amps its putting out is a good idea. That could be the issue.

Thanks for the suggestion.

I don't have a designated ammeter, assuming a standard household multimeter should work? I've got a few so I could set it up like the FSM suggests (with a spare set of hands or 2) to measure voltage and amp output.

Depending on how long my cables are I might disconnect the big cable (cable B) off the alternator, I think it has a ring terminal, and use alligator clips on the multi-meter to clip onto the post of alternator w/ one and ring on the other to complete the circuit. Or I can run out and grab some fresh cable and make up a new one to run it to the battery.
In the first reply in this topic, I suggested the alternator could be going bad, you either didn't read my reply or you decided not to check the alternator and or I couldn't possibly be correct.
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Old 01-21-2025, 08:02 PM #24
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Also as Auseeker suggests there are other previous comments that could help you (free charge sys test from the auto parts store?). Why don't you reply back here after you have tried all the procedures offered, and let everyone know what caused your issue.
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Old 01-22-2025, 11:31 AM #25
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Quote:
Originally Posted by AuSeeker View Post
In the first reply in this topic, I suggested the alternator could be going bad, you either didn't read my reply or you decided not to check the alternator and or I couldn't possibly be correct.
I don't disagree alternator could be going bad. My understanding of electronics is limited. My go to cliche is enough to be dangerous and not enough to be useful. As I stated in a few of my replies, I'm open to the idea that my assumptions have been wrong the whole time.

Initially I was trying to diagnose why I was seeing a difference in voltage on my OBDII scanner and my multi-meter. Now that I have identified my OBII as being bad and am getting consistent readings both inside and out, I've moved on to the next step of my diagnosis. Might not be the most efficient method, but I'm working with what I have with the time available to me.

Other assumption I've had, and again could be wrong, is that mid 13+v (while less than ideal) should be sufficient to not have a persistent battery light. Or at least have an intermittent light or go off every now and then when I get a spike higher in the 13s.

I thought by testing the voltage with a multimeter at the cables was "testing" the alternator. If there is a better way or alternative way to test it I am open to the idea.

In my past experience when an alternator goes, it usually goes pretty quickly, again could be wrong. Mine has been this way for 6months now, keeps battery charged fine, car starts without issue (even in current string of below freezing temps). All the cables and grounds I can see look good, so I was trying to see if there was another wire or fuse somewhere I wasn't aware of that I should check.

I wasn't trying to dismiss your idea, just needed a little more than the alternator is going bad. Again, not saying it isn't, just trying to diagnose before replacing.

Appreciate the help.
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Old 01-22-2025, 11:40 AM #26
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Quote:
Originally Posted by Runnin on E View Post
Also as Auseeker suggests there are other previous comments that could help you (free charge sys test from the auto parts store?). Why don't you reply back here after you have tried all the procedures offered, and let everyone know what caused your issue.
Honest question.

Is it preferred on this forum to only post back after finding a solution, or throughout the diagnosis? I don't post often as I've had minimal issues that require a post, but personally get frustrated by the questions with no resolution. So I thought walking through my process might spark something in someone in the future. I'm just a regular DIY guy on a budget trying to keep his car alive as long as possible. I've seen both, long threads that are hard to follow (maybe this is one of them), and short threads with no outcome.

Initially I was trying to diagnose why I was seeing a difference in voltage on my OBDII scanner and my multi-meter in the engine bay. Now that I have identified my OBII as being bad and am getting consistent readings both inside and out, I've moved on to the next step of my diagnosis. Might not be the most efficient method, but I'm working with what I have with the time available to me.

I will / can take it to an auto store and have them test the alternator. Part of it was that I want to try and learn more about the electrical / charging system and diagnose the problem myself. Understand what the thresholds are that set off the "battery light", where the ECU gets those values, read those values myself, then determine whether or not the alternator is the problem or something else.

Especially as it isn't currently effecting my daily driving or left me stranded (at least not yet).

Appreciate the help.

I will report back once I have more information or something new.
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Old 01-22-2025, 11:56 AM #27
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Quote:
Originally Posted by Dave4RCR View Post
I read in a post that you can get the volt measure from the alternator by connecting the multimeter to the alternador post. It’s easily accessed you just need to remove the plastic cap.

Now. If you follow the Alt-S fuse in the engine bay, there are 3 wires that connects to a plug just below the alternator post. I believe the PIN4 is the one that goes to the computer.

See attached
There are a couple of other alternator plug threads so I'll continue over there, but my plug only has 3 wires, not the 4th lower right ECU wire. So when I get a chance I'll try to figure out which one feeds the ECU. Hardest part is access to the alternator side of the plug while the engine is running, especially without a lift / garage, not to mention it has been stupid cold.

Might try to find a matching plug online and make up a test harness so I can have better access to the wires. Other than check engine light and maybe a few other codes, shouldn't be any problems running unplugged?
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