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Discussion Starter #1
So my 2002 V6 Limited recently started a no-crank failure. Turn key to START and the engine doesn't crank. It was intermittent for a couple days before becoming solid dead. Car runs fine if I force it to start by hot-wiring directly to the starter solenoid, but it won't start on it's own.

First thought was burned up contacts in the starter solenoid. That's not it.
Second thought was the starter relay in the fuse box behind the left headlight. That's not it.
Third thought was the PARK/NEUTRAL interlock switch on the transmission. That's not it.

Here's where I am right now...

The starter relay is not pulling in when I turn the key to START. The high side of the relay coil looks fine and gets 12 in START (as it should), but the other side (the ground side) of the coil seems to be floating. That low side of the relay coil is connected to the transmission selector switch, and (I believe) is supposed to be pulled to ground through the transmission position selector switch.

I've confirmed the transmission selector switch is connecting it's two interlock pins correctly when in PARK or NEUTRAL, but the ground side of that switch seems to be floating when I believe it's supposed to be tied to ground.

So here's the question... Here's a pic of the connector for the transmission position selector switch. Where does this WH/BLK wire on the transmission selector switch (upper left in the pic) supposed to go?
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I would have guessed it would go to one of the ground junction blocks behind the left headlight with a whole bunch of other WH/BLK wires, but I can't find any connection there. I find it hard to believe that just one wire went belly-up in the middle of a harness somewhere:
303310


So where's that WHT/BLK wire supposed to go?

Anyone have a wiring diagram for the 2002? I've got 2005 but it's significantly different and of little help.
 

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According to the 2001 wiring diagram for the 1MZFE, it connects to ground point EC, which is described as being on the right side of the surge tank, which seems to be their name for the upper intake plenum, no doubt nearly impossible to get to next to the fire wall. At least one other wire, white-black from the igniter grounds, also attaches there, apparently at the lug since I see no splice called out.
Yes, the 2001 to 2003 wiring is very different from the 2004 to 2007 in many areas.
 

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Discussion Starter #3
Thanks much for the potential tip. I'll check for that ground today and let you know what I find.

I had already pulled a couple ignitor connectors off and verified that the W/B wires on them are correctly connected to ground (somewhere). I didn't trace them to any specific ground, but I did confirm that they are grounded. Point is... If the transmission selector shares a ground lug with the injectors, it's not like that lug is completely off.

Thanks again for the help. I'll keep you posted!
 

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Discussion Starter #4
C R, I found the ground in question, and that was the problem. Thank you very much for helping with the scavenger hunt! It's easy to trace something that exists. The problem I was having is that without any documentation, it's impossible to trace something that doesn't exist!

So here's the ground lug on the right side of the surge tank. Clamped under one of the nuts holding the adjustable air vane to the end of the plenum:
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I measured no continuity to the WH/BLK at the transmission switch. Took it off and really dug the meter lead tip into the mounting lug. Still nothing:
303408


There are actually four ground wires shared by this lug. The two at the right don't look good to me. So I dug the meter tip into the remains of the wires and got continuity!!! Kinda hard to see in the pic, but I'm digging the tip of the meter lead into the wire on the right end:
303409


Those two wires on the right side were very corroded and one of them (the one that is supposed to ground the transmission selector switch) had completely disintegrated into dust. Looked like it was connected to the naked eye, but, in fact, was and open circuit.

So I cut off that part of the lug, made an extendo, stripped back the insulation a little on those two ground wires and crimped the extendo into place:
303410


Problem solved!! It's not pretty, but it's what I had laying around here:
303412


Car starts fine again and the low (ground) side of the starter relay is now rock solid like it's supposed to be.

Thanks again for the help with the documentation!! Much appreciated!!
 

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OV, impressed you still have the old girl! I appreciate the MacGyver fixes!
 

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C R, I found the ground in question, and that was the problem. Thank you very much for helping with the scavenger hunt! It's easy to trace something that exists. The problem I was having is that without any documentation, it's impossible to trace something that doesn't exist!

So here's the ground lug on the right side of the surge tank. Clamped under one of the nuts holding the adjustable air vane to the end of the plenum:
View attachment 303407

I measured no continuity to the WH/BLK at the transmission switch. Took it off and really dug the meter lead tip into the mounting lug. Still nothing:
View attachment 303408

There are actually four ground wires shared by this lug. The two at the right don't look good to me. So I dug the meter tip into the remains of the wires and got continuity!!! Kinda hard to see in the pic, but I'm digging the tip of the meter lead into the wire on the right end:
View attachment 303409

Those two wires on the right side were very corroded and one of them (the one that is supposed to ground the transmission selector switch) had completely disintegrated into dust. Looked like it was connected to the naked eye, but, in fact, was and open circuit.

So I cut off that part of the lug, made an extendo, stripped back the insulation a little on those two ground wires and crimped the extendo into place:
View attachment 303410

Problem solved!! It's not pretty, but it's what I had laying around here:
View attachment 303412

Car starts fine again and the low (ground) side of the starter relay is now rock solid like it's supposed to be.

Thanks again for the help with the documentation!! Much appreciated!!
Glad I could help keep it running well.
 

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Discussion Starter #7
OV, impressed you still have the old girl! I appreciate the MacGyver fixes!
AV, Good hearing from you and glad you're still lurking!

She's still plugging along and at about 250K miles now. I've exceeded the goal I set for myself back when I was fixing the whole burned valve debacle. Other parts of the car are falling apart (like this wiring issue), but the engine itself has been rock solid!! Still using no measurable oil between oil changes. As a matter of fact, this wiring issue is distantly related.

You see... She's been running so well, that I decided to treat the old girl to a new set of plugs. So two weeks ago I was wretching around back there pulling the PCV tube and stuff out of the way so I could get my hands back there to change the plugs without pulling the plenum off. I'm assuming during that process, I disturbed this already corroded wire and caused the issue. It was intermittent... For a couple days. And then it went full time no-crank.

So it's a typical case of "No good deed goes unpunished." I decide to toss a new set of plugs at the ol girl and what do I get for my troubles? This no-crank issue, and an intermittent P0442. The plugs I took out looked the same as the day I put them in over 60K miles ago. I should have left well enough alone! LOL I should know better.
 

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Discussion Starter #8
And I probably shouldn't tell you any of this, but wait... It gets worse.

When I was diagnosing the issue, as soon as I traced the issue to the low side of the starter relay not being pulled to ground by the trans selector switch, I assumed the selector switch had gone intermittent. I see pics all over the internets of crusty intermittent selector switches that people had opened up (held together by screws), cleaned out, and put back together.

I figured that's what had to be wrong with mine. After all... The other side is just connected to ground, right? Nothing ever goes wrong with that. It's just a wire. The switch has to be intermittent, right?

So I spent two frustrating days just getting that rusted/corroded switch off the trans selector shaft. Even had to make up a special puller fixture to thread onto it and use a jack screw to get the durn thing off the tranny. What a PITA. But, as we all know now, it wasn't ever the switch at all.

Oh, and at some point (before 2002) they stopped using screws and just riveted the clamshells together. So I drill out all the rivets and put it back together with screws. At least now I know the insides of my selector switch looks great and it's now screwed together in the unlikely event that I ever have to go back in there in the future.

So if my wiring wasn't enough of MacGuyver for you....

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My antilocks are kicking in when pulling out from a stop. I assume I got rusty nuggets across some of the VR magnets.
I got that intermittent P0442 I haven't tracked down yet. (I got until December before I have to pass an emissions test.)
The PTC's in all my window motors are going bad.
My droopy sunvisor was driving me nuts so I pulled it off and now it lives on the workbench.

The ol' girl starts and runs great and she's got new plugs!! (y)
 
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