2006 4.7, No Crank, No Start

I'm still trying to get my truck back on the road. Took it to the Toyota dealer for diagnostics and they ignored my detailed explanation of the situation. They started throwing around the costs of various things I could have them fix, but the word "thousand" (as in $$) came up so many times that I picked it up, paid the basic diagnostic fee, and came home with it.

I'm on my own.

What I know so far is that I've got low voltage (8-9 volts) at the starter relay.

{11/17/2024 EDIT: I discovered later that this is incorrect... I did NOT have low voltage at the relay.}

I have the same low voltage coming out of the ECM to the starter relay. I think that the voltage supply to the ECM must be low, and don't know how to troubleshoot that. Can anyone help?

On the same vein... I put a new alternator in the truck 3 days before this problem began. (intermittent no-crank, no start) Is it possible that the alternator could be the problem? If so, how? My voltage per the gauge on the dash appears normal, and I've no warning lights.

 

I’ve been thinking bad connection, poor ground, or broken wire this whole time with your symptoms. If you changed the alternator 3 days before this all started, I would push it up to the top of the list of potential problems. Have the alternator checked and recheck the wiring to and from. Guessing the alternator is a rebuild? Alternator and starter rebuilds are more miss than hit these days.

 

Was it Denso?

 

This ^^

Reinstall the old alternator. See if the issue persists. And if you made the mistake of buying an aftermarket alternator from an auto parts store, kick yourself for us. Aftermarket parts quality is utter shit these days. DOA parts, defective parts, and short-lifespan (hours/days) parts are commonplace nowaday. It's what we've let manufacturers get away with in exchange for lower prices. thing is, they keep raising the prices and lowering the quality until people start complaining. But the only people who hear the complaints are at the parts store, so they DGAF.

 

I bought a reman Denso alternator from Rock Auto, and installed it Saturday. The problem did not go away. Here's an interesting twist... while testing voltage, I found that if the key is in the on position, and I pull OUT the starter relay, something on the top passenger side of the engine starts "running". Forgive my ignorance... I have no idea what it is... it sounds like a vacuum pump or some such. When I plug the starter relay back in, it stops. Here it is on video. https://youtu.be/rPsld6Lz-Y8?si=idD9KzrRWJ_ZNbsS

Is this normal? What is happening ?

 

Without checking on my own truck or cracking open the wiring diagrams, the only things that make sense making that noise on that side of the engine would be the vacuum solenoids for the secondary air injection system (which are the little boxes sitting above bank 2 cylinder 4 with all the vacuum hoses), or maybe SAIS pump? Only other thing I can think of over there is the ABS squid, but audio makes it sound like it's square over the passenger side of the block. If you put your hand on those solenoids I'm talking about, do you feel them humming?

You're certain that's the starter relay you're pulling out?

 

And this one is not identical to yours, but it shows one way of testing the starter by manually jumping juice to it at the relay socket (start at 9m49s mark if it doesn't auto-jump)

https://www.youtube.com/watch?v=6Dm9W0XR4I0#t=9m49s​

 

Probably the SAIS system.

 

Should it be activating like that when the relay is pulled out? Or is that an indication that there is an electrical connection that there shouldn't be?

 

Yes, I'm positive it's the starter relay. And ever since the beginning of this issue, if I use a jumper wire to apply 12 volts to the starter via the relay plug socket, it activates the starter every time, no hesitation. Is there any sensor for temperature that would affect the starting process? The truck always starts when it's hot and warmed up, and always starts when it's cold. But for a period of about 30-60 minutes after it sits, it goes into "no-start" mode.

And I can't for the life of me understand why that SAIS system (or whatever it is) would turn on when the starter relay is removed while the key is in the ON position.

 

I can’t either but given my situation with starting oddities lately, I’ve decided to order a name brand starter relay from a reputable source (Bosch, whose relays I’ve used for eons for auto security/audio applications). RockAuto had it cheaper than everyone else, and this part is good for 2005-2006 running the 4.7L like you and I. I checked all the local chain stores and none of them had it at a reasonable price, and worse yet, I’ve seen other brands (i.e. not Bosch) not work on our trucks despite counter jockeys telling members otherwise.

If you’ve got the time and inclination and want a sub-$15 test, you may consider it. And I’m honestly not sure what is spinning up when you unplug the relay. Haven’t checked the EWD to figure out how or why anything would get fed anything, but this isn’t the first time someone on here has unplugged a relay in the engine bay and heard noises. I’ve always been shit at reading the EWDs.

 

I replaced the Denso relay (presumably the factory original) with two different relays I got from Rock Auto... I don't remember the brand. But there was no difference between any of them, so I put the original Denso back in and that's what I've been working with.

 

I just found out that when the truck is in it's NO-START condition, and the key is turned to ON, and the starter relay is removed... there's no activation of the SAIS system (assuming that's what it is). There's no noise at all, as would be expected.

I also have found that if I remove the starter relay, turn the key to ON, and apply 12volts to the starter relay, the starter turns but the truck won't start.

It's giving a camshaft position sensor code (P0340) right now. It was NOT giving this code for the first month that I was dealing with this problem. The code popped up after I replaced the alternator over the weekend. I haven't had a chance to look into it, but it's possible I did something to cause that code.

 

Yup, you're not the first, nor the second to pop the same cam position sensor code during no-start conditions.

 

I'm stuck at work, was driving the truck, thought I had some things figured out... now it won't start. But I just unplugged the camshaft position sensor and it started. Wouldn't run. But I plugged it back in and it started up. That's the first time that messing with the sensor has made any difference. I've got a new Denso sensor coming in on Friday.

 

Awesome. I’ll be anxiously watching this one, because it may be what I’ve got going on. And frankly, it may be what a lot of others have had going on also.

 

Also: https://www.tundras.com/threads/camshaft-position-sensor-a-bank-2.123418/#post-3162361

 

This is the camshaft position sensor I replaced tonight. Bingo.

And the more I think about it... I can guess what happened. When my friend (the mechanic who did the timing belt) put the front timing cover back on, the sensor wires got caught and were rubbing on something. I'm guessing there must be a shroud molded into the timing cover, to protect the sensor wires somewhat from the timing belt, and he got the wires pinched up under it. So I'm going to take that cover back off tomorrow night to make sure I didn't make the same mistake.

 

Well, that was likely the cause of the P0340 at least.

I should, for science purposes, unplug the camshaft position sensor and see if I get click-no-start. If so, I guess there's two front-most sensors that need checking (at least on the later year 1st gens when you get the no-start-click.)

 

Mine starts with it unplugged, but it runs rough and dies after a few seconds.

 

It was stupid of me not to determine exactly what the old sensor was rubbing on before I closed everything back up and zip tied all my cables out of the way of the belts. Now I'm concerned that I could have done something that will wreck the new sensor in the same way as the old one.

I've looked at several videos online... it doesn't make sense now that the pinch on those wires would have come from the plastic timing cover. But it's obvious from the marks on the wires that they were all rubbed by the same straight edge of something. My best guess is that it's from the water pump replacement somehow, as he changed that out at the same time. But since all I did was change the sensor (i.e., no water pump or other work), and I visually verified that the wires were clear after I installed it, I should be in good shape. I'm going to pull the grommet out of the timing chain cover and stick a borescope camera in there before I drive it anymore though, to make sure that it's all good.

 

The cam position sensor is supposed to pass thru a rubber grommet in the timing cover, and the plastic clip at the end of wire is somehow supposed to lock onto something, to keep it from touching anything moving.

 

Someone previously busted the clips for the wires you're referring to, so they were all zip-tied in place, I had to cut them free to replace my cam sensor. I've got them all zip-tied back out of the way. I'm talking about the red/black/white wires that come into the sensor itself, where the copper is exposed on those 2 pics. I think my mechanic must have somehow gotten the water pump hung up on them when he put the new one in. That looks like the only thing that could have rubbed out and exposed the copper in a straight line across all those wires. You can really see it well in my first picture, the one that's not as zoomed in.

 

Gotcha, yeah, not sure how that happened.

IIRC, there are two bolts holding the sensor to the head and/or block where my yellow lines are here. The clip I circled in red is supposed to act as a tether to hold the wires back and away from harm's way. I can't rembmer the orientation of the sensor, but I feel like it'd have been rubbed by the timing belt, most likely. It wouldn't make sense for it to be rubbed by the cam itself. I'm quite certain the side that's touching your middle/index finger's fingerprints is what reads the little tab protruberance on the camshaft, so know when it's rotated.

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This is the tab it reads, IIRC. If this tab gets snapped off on the driver's side, you're pretty much fucked. And somehow, I've seen a lot of people snap that little bastard off.

​

 

PS - I finally figured out my no-crank click-with-key-at-START problem.

Damn battery terminal. It was the faintest bit loose where the main fatty alternator wire's copper lead connected to the allenhead on top of my battery post.

I don't dispute my cam sensor may also be getting flaky. But ... my issue was purely battery cable. I could hear it click when it wanted to start, then after 3 seconds, I could hear the solenoid click back.

 

Cool. At least you didn't take the same route I took. On the way to figuring out it was the cam sensor (most likely), I removed my remote start, changed the starter, ignition switch, ECM, starter relay, alternator, and battery cable clamps. No way I'm getting rid of this truck now, it's practically new.

 

Oh believe me, I went down the rabbithole. I have a new cam position sensor in a cart loaded up, ready to go. I'm suspicious it may be failing, flaking out, and it may be causing another issue I deal with periodically with another sensor.

I still plan on cracking open the FSM this weekend and digging thru no-start situations, cam/crank/knock sensor diagnostics. I've got something unusual happening, and I notice my cam position sensor bracket is fucked up also.

 

Here's a great picture of that sensor. I'm 99.9% certain that mine was caught on the edge of the water pump when the pump was replaced.

 

I'm wrapping this thread up. The truck is running, it appears that all is well now, which is what I expected after finding that rubbed wiring and replacing the camshaft position sensor.

Lessons learned...
1. The camshaft position sensor can be the cause of a no-crank, no-start problem on this truck.
2. The starter relay apparently does not need 12 volts, and likely is only calling for approximately 8-9 volts. Was never a part of the problem.
3. Before changing out a starter in this situation, always try a jumper wire first. That would have saved a ton of work and money.
4. Note that it is possible to catch the sensor wires when replacing the water pump.
5. I should have figured that my problem was related to recent work that had been done. I should have retraced every step in the water pump/timing belt repair, to the point of disassembling it again. Had I done that, I would have seen the problem. Otherwise, the cam sensor was buried in the engine and not visible.

Thanks, Shifty, for all your help...!

 

YW. #5 is Occam’s Razor. We all try to hammer it into ppl here but it doesn’t always stick.