2006 4.7, No Crank, No Start

Hi all, and thanks in advance for any help you can offer.

My 2006 Tundra 4.7 V8, 245K miles, double cab has me stumped. First of all, I'm getting intermittent no-crank, no-start. It occurs randomly. Usually no click, but a few times I've heard a single or double click under the hood while turning the key. All other indications are good... lights on dash, accessories, headlights... all work.

Here's the background. 4 weeks ago a full-time mechanic friend changed the timing belt and water pump, I assisted. No problems. A week later, the voltage gauge started showing that it wasn't charging properly, but it was a random intermittent thing, so I assumed the alternator was going bad, and replaced it within a few days. It solved the charging problem. A week later, the truck wouldn't start one day when my daughter was out driving it. I went to rescue her, assuming she had left the lights on. I tried to jump it, but nothing, just a click. "Uh-oh.. it's the starter..." I thought. I couldn't find the starter, but started clanking around, hoping to jar something and make it work. Boom, it started up within a couple minutes. I cleaned the battery terminals, drove it for a couple days and the same thing happened a few times, I got it started each time. So I changed the starter out with a remanufactured starter from Toyota, and finished that job 3 days ago. What a miserable job it was. Tested the new starter before I put it in, and tested the old starter after I took it out... both tested good. Uh-oh.

After the starter replacement, it started right up and I had no problems for several hours of driving and doing errands around town. Then it dumped on me again, and wouldn't start. I got a ride home, came back in an hour, put jumper cables in it, but it just clicked. 15 seconds later (jumper cables still on and hot) I tried again and it started as if there was nothing wrong. I got it home and it's in my the garage

I took the battery to NAPA and had it tested. Tested good all around. Cleaned every ground I can find in the engine compartment. It still wouldn't start. Juggled and fiddled with wires and battery and park/neutral and ignition and relays for an hour. Nothing. Came back an hour later, and it started right up. Came back an hour later and nothing. This morning I tried it and it started right up.

I need advice from someone smarter than me. I'm a shade tree, DIY YouTube mechanic, for sure. In the past 2- years, I've replaced the following in this truck: steering rack, blown power steering hose, ball joints, fuel pump, radiator, brakes, battery, O2 sensor, timing belt, alternator, water pump, starter, serpentine belt, blower fan. So I can get some things done. But that's mostly plug-and-play stuff, I know nothing about electrical, and have never had any training or mentoring in auto mechanics.

Can anyone give me some guidance?

 

I'm going to guess your mechanic friend fucked something up, and it's your mechanics responsibility to fix that.

It could be anything, but it sounds electrical, as if a contact is shorting. You're maybe the 1,000th person I've seen here go through the pain of changing out the starter when the starter was absolutely not your issue, and it's easy enough to test that theory without lifting the intake manifold. You can jumper the starter at the starter relay and see if it turns over. If so, likely not the starter. Some people have found forcibly grounding the ground pin of the starter is required (IIRC?)

So, first things first. This likely has nothing to do with your issue, but it's absurdly common to make the idiot mistake of mis-routing the crank position sensor wire when doing the timing belt. It needs to go behind a specific bracket, and the "mechanic" doesn't properly tuck the wire away away and gets rubbed by a belt (pic), correct routing info here. Given this happened within a couple weeks of the job, I would be highly suspicious. That sensor and its wiring harness must be in good shape or the ECU won't engage the fuel pump, and you won't get fuel delivery (but it should crank).

Second. Improperly clamping on a wire would do this too. You technically only need to unbolt the alternator and set it to the side when doing the water pump. Some people will disconnect it completely. You really need to make sure he fully bolted down the connection, and it hasn't gotten tweaked. Easiest way to access (IMO) is through the front apron, from the wheel well, but you can also kinda see from underneath if the skid plate is off.

Third, some things will cause a no-fire condition. I can't ever remember if it's the 2000-2004 or if it's 2005-2006, but if the ECU can't read the coolant temp sensor, which the ECU version is next to the throttle body on the passenger side (usually green), it supposedly won't crank. I would unplug it, jiggle the body of the sensor it to make sure it isn't broken, then make sure the plug is fully secure.

You need to look at every single sensor on the front of the engine and make sure they're secured properly, and not loose, because plastic tabs LOVE breaking off connectors on any vehicle over 10-15 years old.

Likewise, since a "click" is typical of starter not getting enough voltage, I would very any ground wires etc. around the truck.

If your "friend" isn't willing to own up on this, I wouldn't call him a friend. Clearly something he did cause this, and you've already blown money throwing parts at something that - while I can easily understand the logic behind swapping - weren't the actual issue.

I almost assure you the issue is with something he did. Either a ground wasn't tightened correctly, or water from something he didn't properly seal is leaking into the valley and messign with the starter and/or its ground/wiring (did you see any water pooling when doing the starter?) or similar.

 

Oh and this thread covers a lot of issues: https://www.tundras.com/threads/so-you-wanna-buy-just-bought-a-1st-gen-tundra-eh.115928/

Beyond that, in the 4th/5th paragraph you can download the factory service manual which will assist you in diagnostics.

Beyond that, you may want to hit this thread and watch the timing belt videos, and see everything this guy disconnects so you know what to check: https://www.tundras.com/threads/timing-belt-master-thread-sticky.107240/

(Mind you, you'd be best to watch a video for 2005-2006 since their V8 is slightly different from the 2004 and earlier).

 

Any corrosion on the battery cables?

 

No, the battery cables have no corrosion.

 

When he asks you that, he's asking about INSIDE the cables. This is why.

It's a common cause of no-start condition. As is improperly tightened cables. As is poor CCA from your battery, battery testing is free at any chain auto parts store and takes 5 minutes, checking for voltage is NOT how you properly test a battery, but a lot of people think "if 13-14v, battery is good!"

 

No, no liquid under the manifold when doing the starter. That sure was a miserable job. Miserable.

Could this have something to do with a stock security/alarm system in the truck? It happened after the alternator failed and was replaced, but that was also a week after the timing belt/water pump repair. My friend didn't remove the alternator, just shifted it out of the way.

 

NAPA tested, cold cranking amps, said it was all good.

 

good point. I'd check under the dash, but i think someone posted a pic of their alarm module near the fuse box.

 

I can go peel back the heat shrink and look, but the cables are really clean as far as I could see underneath. I'm in Alaska, is pretty dry air here, virtually no rust anywhere on undercarriage, no salt on roads, and I've kept the terminals pretty cleaned up in the 4 years I've owned the truck.

 

Factory keyless with the glass break sensor in the dash left of the steering wheel? Doubt it. Some dealerships also added security systems on (KARR, SECURIKEY+) that were problematic. But no. I doubt it. I think something got loosened or otherwise f'ed up during one of the maintenance tasks recently. It's the most logical situation. And inner wire corrosion, I believe is what killed my factory alternator, like 3-4 years ago, when my 2006 only had 60k miles on it. Fucker caught fire. I'm lucky to have a truck.

But yeah. I would highly recommend you re-check every connector on everything, everywhere, at the front of the engine. I suspect you have a loose connector, or something got brittle during install (sensor, its wire connector, or similar) and cracked, isn't sitting properly. But I've been wrong before.

 

Check your crank sensor wire for misrouting and chafing on the serpentine belt

 

Thank you, I will do this. Most specifically, the problem began right after I installed the new alternator, although the timing belt/water pump was only a week or two before.

The truck is sitting in the garage now. Every time I've tried to start it throughout the day yesterday and also this morning, it has cranked right up, no problem.

 

Then this opens a whole can of worms. And a lecture, with no judgment, because I'm in no place to judge, only to share.

If you got the alternator from the parts store, you need to strongly consider this problem is a direct result of the poor quality of parts most parts stores are selling these days, i.e. your replacement alternator is shorting out internally and you've just shot yourself in the foot. During the last decade or so, aftermarket parts have absolutely gone down the fucking shitter, to be blunt. They do virtually no quality check on the parts beyond checking to see if the part is DOA, and sometimes they don't even check for that. Basically, companies are taking cores, freighting them by boat overseas to be rebuilt in sweatshops, and sending them back untested, knowing they're selling them cheap and if they're bad, the customer will bring it back.

This is why you'll see a lot of people on here tell you: ONLY BUY OEM BRANDS. That doesn't mean, "Only buy from the dealership". That means, buy from the company who made the original factory part. For Toyota, with most of the sensors and other electronics on charging/AC/ignition/fuel/emissions, that will be DENSO brand.

And when you buy, you can't just buy from anywhere, you need to avoid sellers with unverfiable supply chains, like scAmazon, fleaBay, WallyMart, Sears, etc. because they CANNOT guarantee their product is authentic and with automotive and appliance parts, counterfeits are rampant. A lot of people on here will tell you, to get the best price possible, buy it from Summit Racing or Rock Auto. If you like free fast shipping and great customer service, Summit is awesome. Rock Auto will sometimes beat Summit on price, but it's a great family operation, albeit smaller so they can't manage the same high level of customer support.

Any time I want to find out what my part number is for electronic stuff, I'll go directly to www.densoautoparts.com and plug in my truck, and look up my part number to find the 'exact fit' part from Denso, if they made it. Unfortunately, some parts like radiators and alternators have been on backorder. You can actually get a remanufactured OEM from the dealership for around the same price NAPA would charge you for the Denso part.

Lastly, don't believe anything a parts store tells you. Some O'Reilly's counter jockey tried telling one of our members on here their shit brand part was "genuinely rebuilt Nippon-Denso remanufactured part", which is total BS. It may've come from a Denso shell/core, but it wasn't rebuilt to Denso/OEM standards. So don't buy that crap unless it comes in a Denso box, from a reputable seller.

Lecture aside, let me ask two things:

1. Do you still have the old alternator? If yes, and it was still semi-functional, you could always try to reinstall to see if that's the issue.
2. BUT before you do that, I can't recall 100%, but I'm pretty sure the truck will start without the alternator's harness connected, and you don't need to jumper any wires - if the alternator's harness isn't attached, and there's an internal short in the alternator, it can no longer short out. If that is true, you can easily do one test to ensure there is NOT a short in the alternator causing your problem. That would be pulling the power plug off the back of the alternator, and running the truck without it. This could be a stupid no-frills way to test without removing the part. Remember, you technically DO NOT need the alternator to do anything except charge AS LONG AS Toyota didn't have some circuit pass-thru of some sort in place on that line.

Last but not least, there's a 130 or 140A box fuse in most of our trucks for the Alternator circuit in the fuse/relay box next to the battery. You should really be checking those to ensure they're not visibly blown. DC are different from AC. Pulling from the reference website I sometimes see others using, It would be part of the MUSB (multifuse), specifically right here, I believe. But I would be checking both of the MUSB side-by-side here, and all other non-spare fuses you see here. I would expect other stuff to be shot, but again, sanity check. My process would probably bee: (1) Verify the fuses visually. (2) unplug the connector on back of the alternator, try to start the truck. (3) if OK, replace the alternator with 130A genuine Denso alternator which is this specific part from Summit, or this specific part from Toyota, which may be cheaper thru that specific dealership than you can get anywhere else, with their discount, free shipping, and no tax.

​

 

No, I don't have the old alternator. I bought it at a local parts store... NAPA, Autozone, or Oreilly's... don't remember which. (Side note... I picked up a starter at NAPA, and wanted it tested before I installed it. Their tester wasn't working, so they sent me across town to another NAPA store. A hassle, but I went and had it tested... and it tested bad. Whew. So I decided to get a starter from the Toyota dealer. It tested good new, and that's the one I installed.)

Since it's an intermittent problem, I don't understand how it could be a blown fuse, since that'd always be blown... ?

I wouldn't be opposed to taking the alternator back as defective. I noticed when it was first installed that the voltage gauge was fluctuating slightly in a way it never had previously. Slightly wobbling, in the center of the gauge. I noticed a couple days ago that it's not doing that anymore.

 

I have some wobble in the gauge too. I would try the test I offered up. See if unplugging the alternator when you can’t start suddenly solves the issue. If so, swap the alternator. Or replace with OEM so you never need to deal with this shit again for 10-15 years. OEM lasted this long, it will last similar next time.

Avoid the temptation of cheaper aftermarket parts. Not even the knowledgeable parts store guys trust them, and you just found out why with the starter. DOA. All aftermarket is utter shit nowadays.

 

Ok .. I've gone over all the connections and wires on the front of the engine and found nothing amiss. So I started at square one, and tested the relay again. I tried two different brand new relays from Rock Auto, but get nothing. But then I jumped the two coppers on the relay panel with the key turned to "on" position... and even though turning the key doesn't engage the starter... the jumper wire immediately cranks the starter. That means it's ignition-related, right?

 

Could mean ECU, or some requirement the ECU needs before it delivers ground to start relay isn’t being met.

Could mean park neutral switch is faulty, will it start in neutral? Not that it’s definitive, just curious, and I’d investigate/test the switch.

Could be ignition but I highly, highly doubt it.

Time to download the service manual. Go to the “So you just bought a 1st Gen Tundra” thread and grab a copy for your year.

Very suspect it happened after what work you described though. And we have seen cases where, for example, the green ECT failing can cause no turnover conditions.

 

Another interesting detail. I can just about guarantee that after the truck has sat for a day or so, it will crank and start, no problem. But then I start it up and drive it for 10-15 minutes, park it back in the garage, and try to start it again immediately, it will start right up. I come back a half hour later, and it won't start. Then, the next day, the same thing. Very strange.

 

That really makes it sound electrical.

Any evidence of rodents? They like to nest under the intake. Starter is under the intake.

 

No rodents. I already replaced the starter. Just did the little exercise I described in my last post, started it up and drove it, let it sit for a few minutes, and it's not starting again. Just tested the power to the relay, and even though it's not starting, the relay is energized to 8 volts when you turn the key, but the starter does not crank. But I can make the starter crank immediately with a jumper wire at the relay. I don't understand how that can be. By the way, I'm getting the same voltage to the relay when it's starting, as well. No difference in the voltage to the relay whether it's starting or not starting. Am I just not getting enough power to the relay? Should it be 12 volts?

 

That’s right. I forgot. I can’t always read back thru.

Heat definitely affects electronic components, especially sensors. if I recall with these trucks, the ECU does a series of checks on various sensors before it will allow start, at which time it will supply ground to the start relay when alls sensors are available so it can energize. At least that is how I’m remembering it, but I’m not in a place to grab the FSM to dig and confirm.

So I’m thinking one of two things.

One, the type of electronics that are most impacted by heat. Anything with a resistor in it. Like the engine coolant temp sensor the ECU reads (separate from where the days gauge gets temp in earlier models), do this test to confirm something for me. It’s the green sensor on the passenger side of the throttle body. When the truck is in a state where it would normally start for you, unplug that sensor and try to start the truck. If it fails to start, go plug it back in. Does the truck start? If it does, replace that sensor with OEM, it may be the problem. We’ve had a couple of guys say they get no-crank when that sensor is fried, but I’ve never been able to confirm. MAF could be another thing with a sensor, I can’t remember if the truck with start if unplugged. I need to try all this shit on my working ‘06 to see how it behaves, but it won’t help me with guys running 2000-2004 trucks.

Two, also consider, as the FSM will tell you, the ECU may be bad. But I’m suspicious. We’ve seen it before, where the ECU prevented starting, when water got into it. But I’m not thinking it’s the case here. Just a gut feeling.

 

I think this is the sensor you were referring to. Yes, the truck will start when this is disconnected, but in my no-start condition, it will not.

I'm getting 8.5-8.6 volts to energize the relay in starting condition, but in no-start, it drops to less than 8.5. Based on what in seeing in the FSM, I need 9-14 volts, I'm guessing it's at the brink of operation, and the slightest fluctuation in voltage is tipping it between start/no-start.

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

FSM seems to indicate I need to replace the ECM. Can you direct me toward a reputable place to buy a replacement and get it programmed. Then I'll find a video that shows how to do it.

 

YES. FS1 is a solid source for fully refurbished units: https://www.fs1inc.com/

Note, if you pop off your glovebox door, slide up your ECU and jot down the XXXXX-XXXXX part number on the side of it (it's in that format five-dash-five, often ending in 'c0'). Use that number to search for the correct ECU at their site rather than using the lookup tool.

I'd just say, tracing back on that line where it's pulling voltage would be a good idea, make sure the line didn't get nicked or chewed, like if rats got in the dash.

 

I've been working on a lot of different boats lately. Sometimes when checking a circuit I'll see ~ 12.4 volts near the battery side, but only ~ 8 volts (or less) at the end of the circuit. This always resolves as either a bad/weak connection (corroded wire, bad crimp connection, etc.), or a bad ground.

 

My '03 Tundra starts with coolant temp sensor disconnected fyi.
It *barely* starts and *barely* runs at idle, but it does crank and start.

If the '04 would be the same, I'd say this doesn't match the behavior OP is experiencing. At least not a temp sensor alone.

 

Figured out which pin to test yesterday... I found that the pin off the ECM to the starter relay was only putting out 8 volts. Ordering a new ECM today.

 

Yeah, I'd be testing that wire run for sure.

 

The truck is fixed and back on the road. It turns out the the ECM was bad. It was fairly simple to replace, and cost me $281 for a new one.

EDIT: Nope, nevermind. See next post.

 

So I put the new ECM in it, and it started right up and ran beautifully. I assumed that all was well and did NOT test the voltage at the starter relay to see that I had 12 volts, so I can't comment on that. But it's in my garage right now and I went to take a drive in it... and it won't start again. Voltage at the relay is only 8.2 volts... I don't know if it was ever 12 after replacing the ECM, and I wish I had tested it. My only thought now is that I've got a really complicated problem that is probably beyond me, and that maybe whatever caused the original ECM to fail has now caused the replacement to fail. Other than that I have no idea. Any help is appreciated.

I've replaced starter, ignition switch, starter relay, and ECM at this point.

EDIT: I checked the voltage again at the starter relay, as it wasn't starting. It was 9.3. A couple hours later I turned the key and it started right up. Tested voltage at the starter relay at that time and it was 8.2.