Voltage at ECU-IG fuse

[CZ75]

What is the voltage at ECU-IG (10A) fuse under the driver side panel supposed to be when the key is turned off? I'm getting 3.1V

Turn the key on and have 12.7V at this fuse.

If the IG1 (15A) fuse is pulled while measuring voltage at the ECU-IG, voltage jumps up to 4.1V (key is still off).

I'm trying to run down a voltage leak in the system after a recent rain.

If someone can check the voltage at this fuse with the key turned off it would help me understand if I have a voltage leak to the ECU.

Thanks!

 

[tklr17]

Created an account to reply to this, I'm actually currently dealing with the exact same thing while tracking down a parasitic draw that I'm experiencing.

I'm getting around 4.5v with ECU-IG and IG1 in, and about 1v more with the ECU-IG fuse removed.

Are you experiencing any kind of parasitic draw off your battery? I'm seeing around a 600mA draw coming from the ECU-B circuit that's related to the backfeed I'm seeing on those fuses. You might want to pull the ECU-B fuse as well and see if that changes any of that behavior.

 

[CZ75]

I should add some background on this:

Heavy rain last week caused a puddle in the driver side foot well when the truck was pointed downhill and in the rear cargo area passenger side when parked uphill.

I cleared all 4 of the moonroof drains over the past few days and have a lot of the interior pulled apart from that process and to dry everything out. This was definitely the cause of this issue.

Key fob stopped working and a ticking sound under the dash occurred when the key is off. Rear window wiper and the parking lights are coming on w/o a key in the ignition.

The matting under the driver's side foot well carpet was still soaked even after using a wet vac on that area last week, so I pulled the carpet up yesterday to dry. Found the firewall mat was also soaked today.

Water ran down the A pillar and poured out the large wire bundle that had a plastic wrap around it.

I pulled each connector shown in the pic below and cleaned with connector spray before going back together. Didn't hear any ticking

This appears to have fixed the problem. The key fob is working again and the parking lights are off. The ticking sound coming from under the dash has gone as well.

 

[CZ75]

Voltages at (RR WSH), (ECU-IG) and (IG1) locations in the fuse box before and after cleaning the connectors.

All 3 fuses removed

- Before - 4.68v @ (ECU-IG) others were zero V.
- After - 4.3v @ (ECU-IG) , others zero V.

(IG1) fuse in, other 2 removed

Before - 4.72v @ (ECU-IG)
Before - 0.15v @ (RR WSH)

After - 4.39v @ (ECU-IG)
All other contact pts were zero.

(IG1) & (ECU-IG) fuses in.
Before - 3.66v @ (RR WSH)
After - 2.0v @ (RR WSH)

(RR WSH) & (ECH-IG) fuses in.
Before - 4.45v @ (IG1)
After - not taken

(RR WSH) & (IG1) fuses in.
Before - 4.60v
After - 3.35V

Charging the battery overnight. Last time it didn't take a full charge. I'm guessing this was because there was a constant drain. I'll look at everything again tomorrow and make sure the matting is dry before putting it all back together again.

 

[tklr17]

I would still highly recommend checking how many milliamps are being pulled from your battery while the car is off before claiming victory here.

The symptoms you're describing are functions controlled by the Body ECU, which is integrated into the back of the driver's side fuse box.

Clicking sound in dash: Flasher relay
Rear wiper: Back Door ECU (controlled by the Body ECU)
Rear lights: Not actually controlled by the Body ECU I think, but the circuit for the rear lights shares a connector (J39) with the constant 12v ECU-B circuit and directly interfaces with the driver's side fuse box.
Key fob: Sends signal to Door Control Receiver, which communicates directly with the Body ECU through 2 signal lines. If your ECU is doing weird things while the car if off it might be ignoring your fob's commands.

The point is, if your Body ECU is receiving any kind of voltage when the car is off, it's going to send out a bunch of commands to make the car do things when it shouldn't. It then gets tricky to diagnose becasue the reality is that these symptoms may not be consistent over time, especially when you're constantly resetting the ECU by disconnecting the battery and those connectors that lead to it. It all depends on what the ECU decides to do while "confused" by the voltage it's receiving when it shouldn't be getting any.

My 4runner is my daily driver so I've had to troubleshoot all this while still relying on it to get around. Just been unplugging the battery every time I park. I'm also seeing the exact same symptoms as you, except my car alarm would randomly go off when the car was off and locked with the batttery still hooked up. I've had all all or some of these symptoms go away for a time, but I could always confirm it wasn't actually fixed because there was still a parasitic draw on the battery. And sure enough, the symptoms always eventually came back. It's been 2 weeks of regular driving since I heard that clicking from the flasher relay and it started up again a couple days ago.

You might be right with thinking it's those connectors by the parking brake pedal (if so, I'm jealous, haha). But if you see a parasitic draw off your battery or those symptoms start coming back after drying out and cleaning those connectors you mentioned, you might want to start considering the Body ECU (ECU-B circuit) or the ignition switch circuit (this is what is technically supposed to provide voltage to all the fuses you're measuring).

 

[CZ75]

Just to clarify, it was the front amber parking lights (always on when driving) that were flickering on and off when the key was out of the ignition.

24hrs after removing the charger from the new battery connected to the vehicle, voltage taken at the battery terminals is stable at 13.02V.

I wasn't able to get that high of voltage at the battery prior to cleaning those connectors. It was in the mid 12v range with charger removed.

I'll check again tomorrow to see how it's holding....

 

[CZ75]

13.01V today... Moved the truck a couple times yesterday so the wife could pull her car out of the garage. I would have expected the battery to be drained some from that if there was still a battery drain issue, but it revived voltage as a battery should.

Pretty confident the problem has been solved! :whoo:

 

[tklr17]

Good to hear!

Pulling mine apart today to see if it solves it for me.

Did you find any signs of water on the connectors or within the plastic wrapping that you removed to expose those wires?

 

[tklr17]

Also, were there any other connectors that you removed that had electrical tape wrapped around them? I see a couple that seem to be part of this whole system but I have been avoiding removing any of tape.

 

[CZ75]

The only electrical tape cut was the tape wrapped around the wire bundle shown in the previous pic. It was only 1-2 wraps with tape. The connector itself was not wrapped. Only the connectors shown were touched.

Unplug, spray both sides with QD contact cleaner and reinsert.

Getting a good amount of rain last night/today so I'm anxious to see if clearing the moonroof drains was successful in eliminating future issues. Fingers crossed...

 

[tklr17]

I had unplugged those connectors before, but never hit them with any connector cleaner and was having a hard time drying everything out because it was so cold up here for a couple weeks. Tried it again with the cleaner but no luck.

I did manage to find the source of the backfeed and draw, but it wasn't those connectors.

There's a connector (J39 in the electrical diagram) inside the interior panel near the rear LH passenger door. It includes the constant voltage and signal line between the Body & Back Door ECU's. It's a pass-through connector pointed downhill.

Turns out it's been slowly collecting water back there for years. I can confirm that because when I bought my 4th gen 2 years ago, the previous owner said he couldn't get the rear windshield wiper to work. Figured it was the motor.

After opening up the connectors and cleaning the corrosion, the voltage backfeed & parasitic draw went away and the rear wipers started working perfectly for the first time in years. The way it's wrapped and positioned, it would be extremely hard for any kind of moisture to evaporate and there's no where for it to drain. Just pools up in that connector and sits. Forever. At least that's the case when you live in a rainforest up north!

 

[CZ75]

I read on another thread about a connector at the driver side rear wheel well. I cut the wrap around the connector and it was dry, so it got taped up again. I never had water accumulation on that side of the truck.

The driveway the truck is always parked on is slanted in a way that the passenger rear corner gets soaked when parked up hill. Hopefully that's in the past now.

No moisture when I checked yesterday and the main battery was at 12.8V.

I also have a secondary battery (Optima yellow top) and it wasn't holding a charge either. It's 15 yrs old and thought that was the problem. It was holding at 10V when I pulled the fuse at the battery separator to make sure there was no connection made between the batteries.

Battery 2 was at 12.2V yesterday when I checked. I'll put the separator fuse back in and see if that battery still holds charge as well. Batt 2 is connected to the cigarette outlets only and can be connected in parallel to the main batt by a switch on the dash just above the fuse box.