Blown fuses and electrical nightmare

[scooterguy]

- It all started with a radio that quit. Found 7.5amp "rad2" fuse blown, replaced it.
- A week later the truck powered down, ignition off, key out and radio stayed on?
- next day, when truck ignition off and key out nothing worked, as in no power locks, no memory on trip odometer, no immobilizer.
- last night I checked all fuses in main boxes and found a 7.5amp "ECU-b" fuse blown replaced it.
- now a few things remain on after ignition is turned off...radio on, "P" light for park remains on, 12v outlets have power???

Please help if you have any insight. Could this be the body ECU?

[czechm8]

Hmmm. Bad voltage regulator?

[JBH1989]

The voltage regulator is in the alternator and is about as relevant as a muffler bearing.

What year is your Sequoia?

The ECU-B and RAD2 fuses are linked. The RAD2 fuse supplies power to the radio through the ACC-CUT relay (accessory cut-off relay). The relay gets power to pin 85 through the ECU-B fuse. I would start by checking the relay, then checking the circuit integrity (looking for a short-to-ground). It's possible, and it sounds like, the relay contacts may have welded together due to a short circuit or being overloaded for a prolonged period of time. The relay is grounded by the engine control module. Remove the relay and verify the radio and others are now turned off.

Pin 1 is grounded by the ECM. With the key off, take a volt meter with the red lead on B+ and probe pin 1 with the black lead. You should have 0 volts. If you have 12v, you have a problem in the engine control module OR the wire is pinched to ground somewhere in the harness.

Pins 2 and 3 are power leads and should have 12v.

Pin 4 is the load, which goes to the radio and other devices.

Now the instrument panel P light gets power from ECU-B but it is grounded by the ECM or the transmission position switch. It has nothing to do with the ACC-CUT relay according to the wiring diagrams I'm looking at.

Next line of thought would be a sticky ignition switch. How many miles are on the car and what kind of driving do you do? If for some reason the contacts in the ignition switch ACC position are closed with the key off, you'll power up the same systems. Check the relay, and then check to make sure you don't have a bad ignition switch.

If you have power to the cigarette lighter (NOT the power outlets) I would highly suspect the ignition switch to be faulty.

[scooterguy]

JBH...thanks for your advice and impressive response. I have not had a chance to try your solution yet as I am out of town. My truck is a 2002 with around 100,000km/60,000mi. I don't drive it hard but at the same time I am surprised by the stupid things that have gone bad with this truck...this problem, rear latch, a/c compressor...what is next? Doesn't seem like the old Toyota quality I was used to...especially for such an expensive vehicle? Anyways, thanks so much for your advice, I appreciate the time you spent diagnosing this issue and will post my results when I get home Monday.

cheers, DD

[JBH1989]

Originally Posted by scooterguy

JBH...thanks for your advice and impressive response. I have not had a chance to try your solution yet as I am out of town. My truck is a 2002 with around 100,000km/60,000mi. I don't drive it hard but at the same time I am surprised by the stupid things that have gone bad with this truck...this problem, rear latch, a/c compressor...what is next? Doesn't seem like the old Toyota quality I was used to...especially for such an expensive vehicle? Anyways, thanks so much for your advice, I appreciate the time you spent diagnosing this issue and will post my results when I get home Monday.

cheers, DD

It seems like a lot but think of it this way:

You could have spent 90 grand on a BMW 7 series, and by 80,000 miles you probably would have replaced the water pump, radiator, expansion tank, thermostat, and catalytic converters. At least it's the (relatively) cheap stuff.

[scooterguy]

Well, the AC compressor is a $4000 touch if I take it to Toyota. I think I can get it done for a thousand bucks privately.

[scooterguy]

JBH...do you know how to get at this relay? I think it is on top of the fuse box under the driver's dash? Anyways, is there an easy way to check this?

thanks, dave

[nem]

Your truck been in an accident? If so look in the crash area for pinched or bare wires.

[scooterguy]

No, never been in an accident.