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EDIT FOR SOLUTION: I discovered the alternator plug was replaced with pin 1 and 3 switched. I’ve held that plug 3 different times now.
Hi,
I’m having the hardest time with my new to me 02 GS430 Build
SYMPTOMS:
On a cold start it runs 15.5 volts and slowly goes to 14.7 as it warms up. Even in restarts sometimes it’s above 15.0.
Key ON engine OFF, there's no "charge" warning light.
No idea how long this has been a problem.
Diagnostics:
I’ve measured resistance on the three sense wires from the alternator to the junction at the ecm box. 0.1 or something ohm. When I back probe both of the battery voltage wires at the junction they read correct.
When pulling the correct fuses ("alt-S" under the hood and "Gauge" in the driver kick panel) listed on the diagram below power/continuity is removed indicating it's not hot wired.
I’ve added a 4 gauge battery to chassis ground and a 4 gauge alternator to ground.
I’ve replaced the alternator.
I've removed the cluster and tested the bulbs.
When looking at the wire diagram the "Service Hints" are incorrect, but when I follow a similar vehicle that does have correct "Hints" I should be getting 0-4 V on the L "Lamp" terminal, but instead I get about 1 volt below what's measured at the battery.
THEORY:
When someone replaced the connector on the alternator they got the L and S terminal backwards. I didn't consider this possibility and didn't ensure the plug was oriented correctly when I measured resistance.
1. So instead of the alternator sending V to the ECM plug E3 pin 15 via the "L" terminal, the alternator S circuit is not grounding like the "L terminal would. so the ECM thinks the alternator is charging and now I get no "Charge" light.
2. At the same time, the voltage applied to the S terminal is coming from the ECM "charge" circut" and is about one volt less than battery (there's a diode in the ECM voltage). This causes the alternator to charge more.
edited for clarity and to bring more information to the top of the thread.
Someone with the same car measure charging voltage so we have a baseline. 14.7 volts is good because there is a small voltage drop going from the alternator to the battery. If you put in big *** wires then you'll be increasing your battery voltage.
The plot thickens. I noticed the discharge warning light didn’t show when the key is on but not running. So I took out the cluster and the lamp tests good.
I don’t know how this would effect things.
Also, early on I didn’t mention I found the alt-s fuse blown. The car was already over charging at that time. I discover this when I was testing for voltage at the junction in the ecm box highlighted above. When I put the fuse in the alt-s I got voltage at the junction.
There was no change of behavior. After the fuse.
I got a TIS subscription and I wish I had just bought the manual. I get to test the cluster to alternator wire now.
Swapped the snow bulb for the charge warning bulb and still no indicator light with the key on engine off.
I can’t imagine this is related to the over charging issue but, it also touches the same system. Is there another way to test that bulb? For example. I know if you jump Tc an E1 at diagnostic port 1 a bunch of lights flash.
Also, I sat with the key on engine off with fan up lights on. The battery voltage dropped to 11. I feel like that should have triggered the light if the cluster was behaving.
Charge idiot lights are usually load based not voltage. I feel like there has to be more to that light than just what's shown in the diagram you posted. It should take awhile before the battery dips to 11 volts you should get the battery load tested or simply replace it.
This post is all about the "L" terminal on the alternator "Lamp." Normally, on say a 91 4runner, the "L" terminal completes the "warning lamp" circuit to ground when the alternator is not charging (aka light is on). When the alternator is charging, voltage is at that terminal and no current flows through the "Lamp" (aka light is off). You can see in this schematic it also shows the cluster CPU deciding what to do with the light. So the ECM sees the "L" and decides what to do about the "Charge" warning lamp and also the DRL.
here’s a similar issue with no resolution. Other thread
Second version of the diagram.
This link describes the L terminal function on the LS400. For the GS430 the L terminal doesn’t go to the lamp, it goes to the ecm. Ls400
The ecm sees the L terminal and decides to turn on the DRL after the alternator is charging.
My DRL turns on with key on engine off, which is wrong. They shouldn't be on until the car is started.
I pulled the gauge fuse and it behaved normally. I pulled the alt-s fuse and it behaved normal.
At this point I feel like it might be the connector. I was able to measure continuity with it unplugged, but I can’t get to it to back probe while the engine is idling.
Also, the above posted "service hints" is wrong. It didn't make sense and when you look at the SC or LS 430 either. The tundra uses the same type of alternator, but with a dummy light. It's "Service Hints" make sense. The circuits that are fused to the battery G2 pin3 "Alt-S" have 12 V all the time. G2 pin2 12 V "ignition" ON, and G2 pin 1 "L" is for a lamp output. It should have 0-4 V if there were a bulb, but I wonder what it should be going into an ECM.
The 2002 Tundra uses a simple dummy light and has the following diagram and service tips.
I feel like this is definitive proof the GS SC and LS "Service Hints" are incorrect. I’ve checked “charging” EWD from an 89 Camry and 4 Runner up to 2005 Landcruiser. Maybe half of the service hints are wrong and half are right. Wild. Several do list the voltage in the L terminal as 0-4 key ON engine OFF.
So I measure about one volt less on the L terminal than on either the IG or the Alt-S terminal. I believe it should be between 0-4v.
If the old service hints are to be taken with a grain of salt, I believe the voltage on the L terminal with ignition on engine off should be from 0-4 V. So why is mine measuring 10.5 V?
Both the GS430 and the SC430 have the L terminal at the ecm E3 pin 15 to be yellow. Mine is brown.... The LS430 is called E6 and uses Pink with blue wire. The 3rd Gen uses CAN and the L and M terminal (very different).
Will someone please measure their voltage IG ON engine OFF? It’s fixed now. I didn’t measure the voltage though.
This is the wire. Mine is brown yours should look yellow. E3 pin 15.
09-28-23, 03:35 PM
15.5 volts on cold start.
