No Crank, Like Attempting To Start In Drive

Scm2017

Member
TB acts like it would if you tried to start in drive. Not getting power to starter and have replaced ignition switch. When testing starter Relay, I get power to one of the terminals(let's call it passenger side) but the other is not showing power to it. Ground works too. Where can I go from here?
 
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Scm2017

Scm2017

Member
Nevermind. Was testing wrong terminal. I went out and checked ignition fuse#34 and it was good. Replaced it and turned key and it started right up. Now I am really lost on what happened and will be waiting to see it pop up again.
 
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Scm2017

Scm2017

Member
Had a master mechanic look under the hood and was told to clean all my wires that had the green corrosion or build up. I didn't think they were that bad. She said that most likely, I was getting a bad ground somewhere and by removing the ignition fuse, it may have disrupted the bad connection(?) and allowing me to start. Guess time will tell.

I just bought this truck for junkyard price and was initially going to use for parts. The original owner thought he had a rod knock but when I got there I told him engine was fine. I told him he just had something loose under vehicle and if he was sure he still wanted to sell it. He was taking to the junkyard no matter what. Turned out that his rod knock was just the heat shields riding loosely on the exhaust.

This truck's engine and trans runs great so I titled it for now as a secondary vehicle.
 
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Sparky

Moderator
Could disconnect the battery, take a pic of the fusebox for fuse and relay positions, then pull them all out and spray down the fuse box connections with contact cleaner. Let it thoroughly dry and put the fuses back in.

I'm (eventually) going to do this to my Silverado. Have not had an issue with mine per se, but it has some cruddy buildup on things and I do get some occasional voltage drops.
 
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Scm2017

Scm2017

Member
The problem has reared it's head again. We checked neutral switch by putting it in reverse and seeing if we had power to starter Relay. It passed.

Does this mean the pcm is acting up and not sending ground to starter relay? Or is there something else to check?
 
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budwich

Well-Known Member
It is unlikely that it is a PCM issue. More likely its a wire connection problem. You need to check that the same voltage you were finding at the starter relay is ALSO making it to the pcm.... that's how the PCM "knows" to send the ground. Of course, you need to check that the ground is indeed leaving the pcm and finding its way back to the relay.... which I assume you have found is not pulling up. Of course, you have checked the relay or switched it with a known working one.

Since you (or your "master mechanic") found that playing with the fuse box "appeared to have fix" the problem previously, it is more than likely your "solution" lies therein... ie. the fuse block / connections therein.

Further, re-reading your posts, you said you only had power at one point on the starter relay at "some point in your travels". Is this still the case? when you try to start, the starter relay needs to have two points of power out of the four contacts... none of these rely on the PCM or its function.
 
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Scm2017

Scm2017

Member
Ok thanks. Will look tonight. I have a friend that is helping me check the fuse etc. as the way electronics work is way above my head.

Yes, we have two points showing a light. I most likely misspoke as I have no clue.

When he looked earlier this afternoon, one thing changed that we did not encounter the first time this happened. In the starter Relay terminal that would light up when grounded(?), it did not light up as it did before. Sorry if my terms are off. I will talk with him and get better terminology tonight.
Thanks again.
 
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budwich

Well-Known Member
Since your last "revelation" (... electronics work is way over my head).... :smile:
you need to actually check to see if there is a ground coming from the pcm during the "try to start cycle / key to start". This is done using a resistance measurement (to a known ground) on the appropriate contact at the relay socket WITH THE RELAY REMOVED.
Hopefully, your friend can help.
 
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Scm2017

Scm2017

Member
We have continuity from crank fuse to pcm and pcm to ground Relay. Not sure what else to check.
 

budwich

Well-Known Member
not being a "disbeliever" but please describe how you did those checks.... plus a recheck of the shift / neutral switch.

still further, you didn't confirm that you are indeed getting voltage at two of the four contacts of the relay during a start cycle.
 
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Scm2017

Scm2017

Member
Ohm/volt tester. Disconnected fuse box and checked the wire from fuse 17 to pcm harness. Same with pcm harness to the wire for starter relay.

Before we disconnected fuse box, we tested with starter Relay and fuse 17 with a circuit tester(?).
 

Mooseman

Moderator
Have a look at this video. Has good troubleshooting info:

 
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Scm2017

Scm2017

Member
Thank you for your help. We have already viewed this video and it was a big help in starting the trouble shooting process.
 

Mooseman

Moderator
Does the security light flash when you turn the key and keeps flashing?
 

Mooseman

Moderator
As per the video, did you try jumping the two terminals to make the starter motor run?
 
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Scm2017

Scm2017

Member
That we did not try. Figured that's to test starter which is brand new. Right now we are not getting the pcm to send ground to starter relay.
 

Mooseman

Moderator
Ah, so the PCM is not happy about something or not getting the signal from the ignition switch. Did you try replacing that? It can be the source of electrical gremlins and isn't expensive to replace.

Another possibility is the Park/Neutral switch isn't working right. If that's the case, the PCM thinks it's in gear. I remember somebody had that problem.
 
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Scm2017

Scm2017

Member
Yes, ignition switch has been replaced.
As for the neutral switch, we tested the relay in park and reverse. In park we got power to relay. In reverse we did not, so we figured it was working.
 

budwich

Well-Known Member
well if you aren't getting the ground from the PCM, perhaps check your grounds associated with that area.

you have confirmed that you have power at TWO contacts at the relay socket during start attempt... right?
 
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Scm2017

Scm2017

Member
Correct budwich on getting the two contacts.

Could it be a bad connection to the pcm c1 pin 20(440 battery positive voltage)?
 
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budwich

Well-Known Member
Overall, I don't think its a PCM problem. As was suggested, pull / check / clean the fuse area. Having said that, anything possible since you don't know the actual history of the vehicle.... the owner might have been somewhat right about a "rod" but it might have been that the engine was running rough due to a PCM issue and the owner just thought it was mechanical.

further, you indicate "continuity at..." but did you actually read voltage at the appropriate PCM pins on the connector.... again at the two appropriate pins?
lastly, we are talking about a 2007 TB right?
 
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Scm2017

Scm2017

Member
Hear ya. Fuse box was pulled yesterday and cleaned. My buddy checked it out using ohm voltage meter just to make sure fuse box itself was good.

We are going to recheck everything again today and go rent code meter, just to see if anything pops up.

Thanks your help.
 
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Scm2017

Scm2017

Member
Overall, I don't think its a PCM problem. As was suggested, pull / check / clean the fuse area. Having said that, anything possible since you don't know the actual history of the vehicle.... the owner might have been somewhat right about a "rod" but it might have been that the engine was running rough due to a PCM issue and the owner just thought it was mechanical.

further, you indicate "continuity at..." but did you actually read voltage at the appropriate PCM pins on the connector.... again at the the two appropriate pins?
lastly, we are talking about a 2007 TB right?
Yes. All I meant by continuity was that nothing was broken in the wiring/ connections.
I will have to ask buddy on actual voltage from pins.
Yes 07 TB.
 

budwich

Well-Known Member
further, at the fuse block, one can do resistance measurements (with the fuse remove) towards the "far end connection"...where you / the circuit "thinks" the voltage is heading towards... the resistance should show relatively the same IF the subtending circuit is similar in design. This will somewhat confirm that the likelihood that the voltage will ultimately find its way there when the fuse is replaced in normal circuit operation. The resistance measurements are done in key off mode. Further, what are your resistance readings for those measurements for the two circuits (that have powering on them in normal operation) heading from the fuse block towards the PCM?
 
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Scm2017

Scm2017

Member
further, at the fuse block, one can do resistance measurements (with the fuse remove) towards the "far end connection"...where you / the circuit "thinks" the voltage is heading towards... the resistance should show relatively the same IF the subtending circuit is similar in design. This will somewhat confirm that the likelihood that the voltage will ultimately find its way there when the fuse is replaced in normal circuit operation. The resistance measurements are done in key off mode. Further, what are your resistance readings for those measurements for the two circuits (that have powering on them in normal operation) heading from the fuse block towards the PCM?
Not sure Budwich. I will show this to my buddy, who will be over in an hour or so. I can have him give those numbers/answers.
 
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Scm2017

Scm2017

Member
Update: I really appreciate everyone's help. With the celebration of our country's birthday, and a vacation up to the Northwoods, where T-Mobile has no coverage, I havent had time to do much with this truck.

We had unhooked the pcm harnesses, to check for any oddities like corrosion or broken wires/connections. I turned the key and the truck started. Totally mind blown, I ran it upto a friend and shut off the engine. She wanted to show me a couple things and when I went to start it......well it wouldn't start. She jumped in and put it in neutral and it started right up. I tried this before to no avail.

If the neutral switch is the problem, then why would we get power to the crank fuse while in park but nothing in reverse? Wouldn't that confirm the switch was working?

I was told to call a customer service rep (neutral switch)to walk me through testing neutral switch. I will be doing that later today when these storms past.

Open on any tips/links for testing neutral switch.

Thanks again to you guys for your help!!
 

Mooseman

Moderator
Maybe try playing with the shifter while holding the key turned. If it works or stops cranking, could be a flaky neutral switch or connection. I'd have to try it on mine to see how it reacts to that.
 

budwich

Well-Known Member
"If the neutral switch is the problem, then why would we get power to the crank fuse while in park but nothing in reverse? Wouldn't that confirm the switch was working?" ?????? you shouldn't get any power in reverse.... only in park and neutral.
 
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Scm2017

Scm2017

Member
Yes. So if we got power to fuse, in park, wouldn't that mean the switch was telling pcm to go ahead and start and that it was working? If we got no power to fuse, in park, then I could see checking neutral switch.
 

Mooseman

Moderator
Lets break it down here. This is what the starter relay terminals are:
(shamelessly stolen from May03LT)
Starter relay terminals.jpg

- Fuse 34, you should have 12v+ at all times.
- Fuse 22, you should get 12v+ when you turn the key to run/crank.
- At the starter relay terminal 86, you should have 12v+ at all times (fuse34)
- At relay terminal 87, you should have 12v+ when you turn the key to run/crank (from fuse 22 and neutral switch)
- At relay terminal 85, you should get ground only when the key is turned to crank (from the PCM)
- The last remaining relay terminal 30, you should get nothing or ground, which is from the starter solenoid.

If the Park/Neutral switch is open (not in park/neutral), you will not get 12v+ at relay terminal 87 nor the ground from the PCM to relay terminal 85. Check both.

So if you're getting 12v+ at fuse 22 but not relay 87, the neutral/park switch is the issue.

To test the starter itself, you can jumper from terminal 86 to 30.

Edit: Corrected for fuse 22 power on.
 
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budwich

Well-Known Member
Yes. So if we got power to fuse, in park, wouldn't that mean the switch was telling pcm to go ahead and start and that it was working? If we got no power to fuse, in park, then I could see checking neutral switch.
I think you are confused as to where the neutral switch is in the circuit... it isn't before the fusing, it is after. As Mooseman points out, powering at the fuse(s) has nothing to do with the neutral switch.... it is only involved in "sending" that power further in the circuitry.

NOTE: in the picture that you posted earlier, there is NO neutral switch shown (only an ignition switch)... which could be the source of your confusion.
 

Gunny5

New Member
Lets break it down here. This is what the starter relay terminals are:
(shamelessly stolen from May03LT)
View attachment 81484

- Fuse 34, you should have 12v+ at all times.
- Fuse 22, you should get 12v+ when you turn the key to run/crank.
- At the starter relay terminal 86, you should have 12v+ at all times (fuse34)
- At relay terminal 87, you should have 12v+ when you turn the key to run/crank (from fuse 22 and neutral switch)
- At relay terminal 85, you should get ground only when the key is turned to crank (from the PCM)
- The last remaining relay terminal 30, you should get nothing or ground, which is from the starter solenoid.

If the Park/Neutral switch is open (not in park/neutral), you will not get 12v+ at relay terminal 87 nor the ground from the PCM to relay terminal 85. Check both.

So if you're getting 12v+ at fuse 22 but not relay 87, the neutral/park switch is the issue.

To test the starter itself, you can jumper from terminal 86 to 30.

Edit: Corrected for fuse 22 power on.
I'm new here and having the same problem. Can you verify that you are not reversing 87 and 86 in your conclusion? IGN E (86) comes through the P/N switch. I was not getting power to 86. I jumped a wire from B+ to 86 with the relay in place and it started right up.

I think you are confused as to where the neutral switch is in the circuit... it isn't before the fusing, it is after. As Mooseman points out, powering at the fuse(s) has nothing to do with the neutral switch.... it is only involved in "sending" that power further in the circuitry.

NOTE: in the picture that you posted earlier, there is NO neutral switch shown (only an ignition switch)... which could be the source of your confusion.
The Neutral switch is in that diagram, just off the left edge of the photo.
 
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