2008 Scion XB
For months, the electrical has been randomly shutting off, and stalling the car while driving at highway speeds, but stalling as if something is loose and will resume driving once the 'connection has been re-made.' Recently I noticed a subtle reduction in power while doing in-town driving, followed by a couple of stalls (after starting, or coming to a stop). Now the car will not crank at all. Turning the key to accessory starts a buzzing noise that is very obviously coming from the relay integration (apparently Toyota-specific), in the engine compartment fuse box. Replacing the relay integration yields the same result... so does replacing the ignition switch.
The battery has been tested at home and at Advance Auto and works well (12.6-ish), all of the 10, 20, 30 and 7.5 fuses in the engine and driver-side cabin have been checked for amperage, and correct placement. All relays in those 2 locations all pass the 'clicking' test when connected to a battery, and they all have excellent ohm readings (170-ish). I've inspected the Fusible Link for broken contacts and it appears ok from what I can see. I've also inspected the ECU for bent pins and bad smells (burnt plastic / computer componnets), though this model of ECU seems impossible to separate and open to inspect so I don't know for sure. Lastly I have a highly-rated, but inexpensive consumer OBD tool which yields no codes whatsoever (before I took the car apart)...
I have not been able to get the starter out to inspect / test (seems stuck to the block). I have also not inspected any of the plugs, but assume I would at least hear a cranking if plugs were the issue.
What could be causing this, or what other components should I be checking? Thanks tons... Let me know where to send the check, beer or baked goods...
That sounds like a problem with a ground because the buzzing you're hearing may be caused by insufficient current on the control side of those relays in the integration relay unit . I think that unit is set up so the relays inside share power from the same source on both the control side and load side of the relays.
You may be able to use the problem of the starter not turning to figure out what's going on here because your starter relay isn't incorporated in the integration relay.
There's plenty of youtubes on how to jump a starter relay.
In your case to jump the starter relay you'll pull out the starter relay and "jump" starter relay terminals 5 & 3 to see if the starter will spin.
Your OEM starter relay has a map on it.
It's wired in like this:
Grab a test light and pull out the starter relay.
If you follow the wiring diagram, the power to the Load Side of the starter relay comes from the battery, and through the 60 amp Main fuse, and through the 30 amp Starter fuse, to Starter Relay socket terminal 5.
So Starter Relay socket 5 has power all the time. It doesn't use the ignition switch or the integration relay. Use your test light to check for Power at starter relay socket 5.
If you have power there, use a jumper wire (or a paper clip) to jump relay sockets 5 & 3.
If your Battery Positive Cable connection to the starter and your Engine Ground connection from the Battery Negative cable are good, the starter should turn. If it doesn't, use jumper cables from the battery Positive to the lug on the starter solenoid where the battery cable connects to it. Then clean up a starter mounting bolt and attach the jumper cable from the battery Negative to the bolt.
Jump the "S" terminal of the starter solenoid with the battery Positive cable lug like this:
If the starter doesn't spin then you have a bad starter.
If it does then you have a wiring issue. (Battery Cables or the wire from Relay Socket 3 to the S terminal on the starter).
But what if the starter spins when you jump relay terminals 5 & 3?
Then the problem is on the "Control Side" of the relay and if you refer to the wiring diagram again, you see that Power to the Control side of the Starter Relay comes from the Battery, then though the 15 amp AM2 fuse, and through the Ignition Switch in the Start Position and to the Control side of the Starter relay.
You can use your test light to see if there's power at Starter Relay socket 1 when the key is in the Start Position. If there is then it's time to suspect the Ground on Starter relay socket 2. I included the Ground Point location of that Ground under the wiring diagram. It's labeled as Ground Point "EB" and it's located on the Left Front Fender Apron.
Is it possible that this Ground Point shares that Ground with some of the Relays in the Integration Relay and maybe there's corrosion or rust or something that's causing resistance?
That brings us back to a Ground issue so maybe check your Battery Negative Ground points from the Battery (and clean them up) to the chassis ground points
Here's the link where I pulled that wiring diagram from
https://www.carpdfmanual.com/scion/
Wow, what a robust answer... my car runs again! I think you're absolutely right about the Ground. The battery ground was / is super clean, but after disconnecting and reconnecting the Starter wiring, the Relay Integration stopped buzzing and the car started up immediately. The only other thing I did differently was remove the square pink 'S' fuses (don't know what they are called) in the cabin driver-side fuse box, inspect them and put them back in...
I did try the paperclip / wire jump trick to all 4 and 5 pin relays, but I am still unsure of where the Starter Relay is on my vehicle. All Scion documentation I find shows a Purple Relay (including your attachment) and all I have is Gray (oil / fuel pump?) and Blue under the hood and Blue and Pink and Beige (Hazards?) in the cabin.
Regardless, thanks tons for your help. I'll be picking up a shirt to support the channel. Any additional feedback to my follow-up would be much appreciated but you've already saved me hundreds of $$$.