My truck died in the driveway several months ago.   I ran it for a couple minutes to move it to the driveway.  When I went to start it an hour later, it wouldn't start. 

I've since been tinkering with it for months.

 

• Replaced lift pump relay.
• Replaced fuel filter.
• Tested lift pump pressure (10psi, low, but should start)
• Unplugged and re-plugged: VP44, PCM, VP44 relay, apps, various connectors I could reach
• Replaced batteries with brand new.
• Added 5 gallons of fresh fuel. 

 

Originally, there wasn't anything I could do to start the truck.  Then I learned how to hotwire the VP44 and the lift-pump relay.  I was able to start the truck this way.  However, if I barely touched the accelerator, it would jump up to a high idle, and stay there. 

 

After all my tinkering, I'm at the point where I can start the truck now without hot-wiring anything.

1. Turn key to run, until wait light goes out.
2. Turn key to start, just a blip. (to start the lift pump)
3. Wait five seconds. 
4. Turn key to start.

 

But I still have this problem where all I get is idle, and high-idle.   I've tried doing the procedure for resetting the apps, but just once.  Did I 

 

I've done some bench testing on my apps.  For the things I can check while it's disconnected, that seems fine.  The wiper/resistance looks smooth on my needle volt meter. 

 

What's next? 

 

Thank you, 

-Mark

 

Test your alternator for excessive AC noise. I've got a feeling the VP44 is fine but the ECM is going south. APPS sensor has two validation switch so as soon as it goes to throttling mode it's now jumping to high idle and that it which means there is an ECM fueling map issue caused from AC noise.

Thank you for the tip.  I went and found your alternator noise article.  I did method #1.  I'm still not getting anything but the two throttle settings.  I have not messed with the ECM or the plug going into it.  Is it worth a shot to disconnect that and re-seat? 

 

I've seen threads saying that ECMs are no longer available.  Are there 3rd party options if it turns out that I need a new ECM? 

this is worth a read.

 

9 hours ago, marked23 said:

 I went and found your alternator noise article.  I did method #1

 

AC voltage was what? We need to hear the results.

I haven't abandoned this thread.  

I went out to start the truck to get the AC voltage, and it wouldn't start.  My usual technique of bumping the starter to start the lift-pump is no longer working.  

 

The ECM is not interested in running the lift pump voluntarily.  I can hotwire the lift pump, but doing so doesn't help. 

 

I've been hunting around for where there might be a bad wire.

Does your wait to start light come on at key on?

 

Hot wiring the pump wont make the pump run?

 

Is the engine turning over and just not starting or not turning over with the starter?

Does your wait to start light come on at key on?

Yes.  The whole key-on sequence seems normal except the lift-pump only running for 1/2 second.  Then I bump the starter, and the lift-pump will run (maybe, maybe not) for another 15 seconds. If the lift-pump runs after the bump, the truck will start.

 

Hot wiring the pump wont make the pump run?

It makes the pump run, but doing that won't make the truck start. 

 

Is the engine turning over and just not starting or not turning over with the starter?

It turns over great.  It just doesn't start.  Actually... it started twice today.  It idled for about 20 seconds each time.   I tried starting it about thirty times.  Never had it running long enough to get a meter on the alternator.

 

Thank you

It is normal for the pump to just bump for 1/2 second at key on. Bumping the starter should make the pump run for 20 seconds or so. Are you sure the WTS light is coming on at key on? What you describe is the classic delayed light with no start until the light comes on. All of this is a function of the ECM. Have you checked for any DTC's?

I finally had the chance to do the AC voltage alternator test.   This test was done without much of a warm-up. 

 

 

It's around 0.070v when quiet, but 0.105v when loaded (charging?).

Also there's a 0.500v spike at the transition, when the load kicks-in. I don't have a scope, would like to see what that looks like.

 

However, I can completely disconnect the alternator and still have this same accelerator pedal behavior.  Interestingly, When I monitor the throttle position on ODB2, I see the throttle move smoothly.  Whatever computer that is reporting to ODB2, that computer is getting a good signal from APPS.  So I would guess that the APPS is probably working fine.   But I still haven't ruled it out for sure.

 

Thank you,

-Mark

I decided to try some random changes to see if anything gets better or worse. 

 

I'm replacing all the battery cables.  I got some of those Fastronix military terminals, some 2/0 wire, and big crimper.

I'm replacing the alternator too.... which just arrived today. 

I had lots of corrosion on/in my battery wires.  I replaced the terminals and the wires.   Also replaced all the block & body grounds that connect directly to the batteries.   The only other wire I replaced was the ground strap that goes from the body to the PCM case.  I also installed a new alternator. 

 

This is my ac voltage with the new alternator.   This doesn't look so good, huh?   I'm not able to drive the truck, so keep in mind that this reading is on a cold engine. 

 

Still no improvement in throttle control, but I'm down to two symptoms.

• My compass thingy above the mirror says "CCD"
• I get code P1689