I experienced code 1688 a while ago and also experienced a dead pedal (completely dead, does nothing).

 

yesterday I replaced the 44 with a new one, got the truck running but the pedal does absolutely nothing.

 

any ideas?

 

thanks,

greg

Have you checked to see if the APPS is plugged in?

Test for Voltage come from the TPS sensor at idle position and WOT.  It should increase from ~0.46 v to ~3.6 v as you increase TPS.  use a paper clip to connect to the wire.  I think it is pin 3 on the 6 pin apps connector.

 

also test for AC noise in your system, regardless of how "new" your alternator is.  Many many many new ones are bad out of the gate.

Edited June 29, 20169 yr by Me78569

Thanks for the responses. I havent yet checked any voltages or if the apps is plugged in as I didn't finish installing the pump until 1030 last night so I'll check when I get off work this evening.

 

alternator was replaced in April but if you can explain how I check for school noise, I most definitely will.

 

I am going to go with tyler's guess,  I am betting the apps is not plugged in completely.

16 minutes ago, Me78569 said:

 

I am going to go with tyler's guess,  I am betting the apps is not plugged in completely.

 

I'll certainly check it. Just seems odd that this happened when it started to run terribly one morning after I started it. I was hoping the new vp would fix the issues but it just made it able to run again haha

What is your fuel pressure?

AC noise is always good to check!

20psi at idle

I should also add that the truck is stock other then a 4" straight pipe and FASS ddrp

That's impressive for a ddrp. I wonder why it's acting goofy.

It's got me stumped. I get off work in two hours, I'll check what was mentioned above. How do you check for ac noise?

It all happened one morning when I was heading to work. Started the truck up, put it in gear then it started running like something that had an aggressive cam and the dead pedal happened the same time. Put a code reader on and got 1688. Tried bleeding the lines through the injector lines and hardly had any fuel come out.  Put in the new VP and it starts great now just still has the dead pedal

You should be able to follow the video above.

I should be looking for the same/similar numbers from the alternator as to what the battery's are putting out? Not the best at electrical

AC noise voltage should be low period. Battery or alternator. The highere either get the more issues will happen like VP44 failures. As for the APPS I would have to agree with TFaoro I'm going to bet the APPS is not plugged in all the way. I've done the same mistake before too.

If I remember correctly the highest you'd want to see when checking A/C noise is .05xx

 

Anything above that and you'll more then likely start seeing issues related to A/C noise. .1 is the MAX allowable limit before the alternator is considered shot, but to avoid any issues and play it safe, we want out alternators to run between .01-.03 as to avoid any problems.

 

Someone please chime in if these are off!

16 minutes ago, Mopar1973Man said:

AC noise voltage should be low period. Battery or alternator. The highere either get the more issues will happen like VP44 failures. As for the APPS I would have to agree with TFaoro I'm going to bet the APPS is not plugged in all the way. I've done the same mistake before too.

Have you seen them come unplugged by their self? I really hope that's the issue but i haven't unplugged it 

In order to swap the VP you prob unplugged the apps.

Really impossible to do a VP44 without unplugging the APPS sensor.

 

Bit of searching to see what  it looks like and I believe you guys may be right. I do not recall plugging that back in. Also I don't remember unplugging it

Edited June 29, 20169 yr by Gregb13