2008 Toyota Rav4 2x4 2.4 not charging alternator and battery good

Guys, I have some unanswered question here and I have looked at All Data and it left me hanging. I have checked the following. Alternator tested out good on the bench test. Charged battery and load tested good also. I have checked all the fuses. I checked the main terminal B from Alt. to the battery to make sure the 120 Amp fuse and the fusible link was good. I checked the Green wire going from the Ignition switch to the IG terminal I had 12 volts. The L terminal appears to be OK because the battery light is coming on saying it's not charging. I also KOhm out the Battery current Sensor it all showed inside specs.

The part I was left with was the RLO Terminal to RLO on ECM and M terminals to the Alternator on the ECM. I have nothing telling me what they should be here. I guessing that something is not letting the power go to the stator to excite it so it will start charging since it bench tested good...So I thinking I either have a bad connection, broken wire or grounded out of the two remaining wires. It might also be a bad ECM. Could anyone tell me what these two should read, please? I have attached a diagram of the system so you can see what I'm looking at.

By the way, looking forward to being a premium member and expanding my knowledge...

i.imgur.com/gk0Q8BT.jpg


Seems like battery current sensor talks to ecm, ecm controls generator field. Is it installed between battery post and generator + cable like in the picture. All the current should be passing though that device.

The meter is on the negative post of the battery and all test checked out OK on it...All within ranges suggested...In the PDF you attached, on the RLO terminal it says (Pulse generation, see 14, 15, and16 waveform) It looks like it might be using hertz frequency as part of the control. I see it monitoring changes in the waveform as speeds of the engine changes.

What does DIV. mean on here? I assume Divided by if I am wrong please tell me. Also, it's not giving RPM ranges on these waves so How do I know when the waveform is bad because it's going to change according to engine speed or what am I looking for on this. I see there a link in blue on Generator is that to the rest of the information about these waves and troubleshooting?

See the hash marks around the screen edges? Each square is a DIV or division.

Horizontally each hash mark, or division is 50 msec. There's 10 hash marks, so it's a 500 msec time frame across.

It's an 8v square wave, peak to valley.

Hold it at 1500 rpms and check for voltage drop between battery positive and alternator post. Then check alternator housing and battery negative.

I would but all I'm getting is battery voltage at all engine speeds because the Alternator is not coming into charge. no signal from ECM, I'm guessing since the Alternator check out fine on the bench.

Are you thinking maybe a bad ground might be causing the problem? I'm asking because I pulled the Left fuse box and checked all the connection there just in case something was corroded on the busbar. When I was pulling in I saw a wire way down in front of the wheel that looked like a ground and the bolt was really rusted. I'm now wondering if it could be a ground wire in this circuit.

I wish I knew what those acronyms were: THB, EIB, IB, VCIB,...

With the car running, read each voltage coming out of the battery current sensor and make it go the opposite with a test light. If you read voltage there, pull it down, through a test light connected to ground. If you see low volts, pull it up, through a test light connected to battery positive. I would go one at a time on each wire and listen for any changes.

Minor wrote: I see there a link in blue on Generator is that to the rest of the information about these waves and troubleshooting?

I was searching for "generator" in the document, that's why lol.

Minor wrote: I saw a wire way down in front of the wheel that looked like a ground and the bolt was really rusted. I'm now wondering if it could be a ground wire in this circuit.

By all means, you don't need my permission to check suspicious grounds.

Well, it's not those ground wires I pulled them all and cleaned them, no change. I have not been able to do the waveforms yet because the car is outside my garage and every time I go to work on it, it starts raining. I spent more time moving my tools in and out than working on it. Ohio weather sucks it has rained for the last 7 days.

Let me ask you this is it possible that the machines in Autozone that I used to get a bench test with, can't fully test computer controlled Alternators right and it may really had a bad regulator.

I don't know how autozone tests alternators.

I don't have a scope to view waveforms but here's how I'd check. Take a regular old voltmeter and measure the voltage on that RLO wire, which I believe is the field control wire. When you're revving the engine up and down that voltage should fluctuate. That should be enough to tell you if the ECM has control or not.

The waveforms were showing 0v - 8v square waves so on your meter you should see around 4V average and should move around.

Or touch a test light, connected to battery positive or negative and see if it flashes or not. If it's pulsing, then try to give the alternator a gentle hit - maybe bad brush contact on rotor?

If it's not pulsing, then I'd check the RLO wire at the computer harness.

If nothing there, then I'd focus again on that battery current sensor.

Just curious, what happens if you leave that battery current sensor disconnected?

The M wire is also worth checking out at the computer. I'm guessing there's voltage on there that goes to the ECM. I worries about an open on that wire.

Find a parts store that has a advanced battery tester that can check alternator, diodes and such when cranking as I haven't had a alternator tested with a bench test machine in years. Not knocking them because I don't know how advanced those are compared to a couple thousand dollar battery / alternator tester.

IF you turn the heater, lights, etc on what kind of readings to you get and does the light stay on or have you not tried that yet.

Loved the days when a alternator was just a alternator but not anymore with all the tech out there. Almost need a engineering degree to diagnose these anymore, well maybe not quite but getting close it seems.

Following along for educational purposes. I've never dug into Toyota systems with battery current sensors before.

For whatever it's worth, I'm not entirely sure that this is a true PCM controlled alternator? :silly: From what jreardon posted, RLO behaves a lot like the FR signal of older Toyota alternators. It's not a command from the PCM to the alternator, but a feedback signal from the alternator to the PCM about alternator load. If it's truly a feedback circuit, then it has no impact on charging rate.

The ALT/M circuit is new to me. The voltage specification chart wants B+, more or less, and doesn't specify any kind of pulse width control. This could be a high/low charge rate command circuit? Just speculating. :silly: Doesn't seem like a true 'command' circuit like we see on other smart charging systems.

My experience with bench testing newer alternators is... It doesn't mean anything.

Well guys, so far my biggest problem has been none of the wiring diagrams have be correct. I think I now have the right one for this Rav4. Toyato decide to have about 4 different setups from the way it looks. All the wire color codes were wrong and trying to figure out from one to another wasn't working. I am attacking the right one in this post for those that are following. You see even in this one there are wires that can be 2 different colors.

After hours of reading on alternator testers and how they hook up to terminals with RLO and trying to figure out wtf RLO stands for, one manual had it defined as Regulated Load Output. Finally! I googled that in quotes and there's an article about it on THIS VERY CAR. Read the last sentence lol.

cdn.ymaws.com/apra.org/resource/resmgr/G...ine/Jan-Feb_2016.pdf

Here's your fix (?):

Any one read Russian? The waveform of RLO and M is pictured there. I don't know if it's known good or known bad. I still don't understand with Google translate on

mlab.org.ua/forum/viewtopic.php?f=10&t=4704

www.testmyalternator.com/en/news/technic...s-tma-technical.html



pmmonline.co.uk/technical/regulator-terminals-what-they-mean/