Found this trouble a couple of places but no for sure solutions.  Mileage on truck is 87,453 and is stock all the way.  No trouble in the past.  Just Oil, filters, tires and battery.  Bought new in late 1999. Old and retired but I like my truck and need to fix it soon so help.  Replaced the lift pump and filter, checked the APPS voltages and are OK,  engine starts quick and idles perfectly.  Touch the accelerator pedal and rpm jumps to approx. 1400 and that is all.  Foot off pedal, goes back to idle.  MIL (engine light) on & all other lights work normal.  Wait to start on and times out as usual.  Code P1689 is all that reads.  HELP PLEASE.

Ebay has some for around $850 and rework for $450.  Don't know if they can be tusted to do the job correctly.

Ordered an ECM today.  Hope it fixes the problem.

I hope so too. I would be interested in who you bought from and how it works  out. A photo of it would be a bonus.

ECM not the problem.  Truck still performs exactly the same with new ECM so what to do next???  I have a couple of questions hope someone can help with.

1.  How many inputs are connected to the ECM ?

2.  If any of these inputs are defective what will be the trouble that shows there is a problem?

3.  Will any of these inputs cause the ECM to not function correctly?

4.  Wiring diagram shows an electrical connection between the ECM and PCM on these trucks.  What is that for?

5.  Someone said to much ripple on the dc voltage coming from the alternator can ruin the ECM.  If so what is the results?6.

6.  What should be the maximum voltage coming from the alternator?

That is a start.  More to come & hope not creating a problem for anyone.

1. iat, map, crank, cam, oil press, ect, app,s think that's it...think

2. apps would be my first guess.

3. not really the ecm will take in bad info. truck might not run, but the ecm doesn't really throw a hissy fit if something isn't right

4.ccd and sci bus to allow communicaiton between the pcm and ecm for things like revs to cluster, coolant etc.

5. When you have too muhc AC noise from the alternator strange stuff happens.

6. typically we want to see under .03v ac 

 

 

do you still have the 1689 code?  

 

 

Have you done an apps reset?

Edited October 28, 20168 yr by Me78569

Thanks for the info.  put a new apps on & reset - no change.   Lift Pump and filter - no change,  ECM - no change, less than .03 v on alternator, code still P1689.

Then if that code is left the computer on the vp44 isn't working as expected.

Is that what is called PSG on the VP44 and can it be repaired.  Noticed there is a place in England that says they repair the PSG5 in the VP44.  Just wondering if this is possible and if there is any place in the states that does this?  Thanks

Very doubtful.

 

 

wire to wire short?

Edited October 30, 20168 yr by Cumminz

Explain in more detail about wire to wire short please.

You said you probe all the wires in the VP harness correct?  

 

If the Psg is good still then I would think your issue is a short in one of the wires between the ecm and vp44

What are the symptoms if the map sensor quits working properly.  Does this have any effect on the operation of the engine.   Thanks for replying again.

One of the pins going to the APPS is labeled "low idle select".  Does anyone know what that signal is and what it is for?????

I've read on bluechip's site that pretty much most of original vp psg's were failing do to lead free solder and too many heat cycles. and internals were not quite as good as they are now. there are some people that claim transistor fails in vp psg's and can be fixed, but I think I would just get a reman one and upgrade fuel system like previously mentioned and move on. 

If the MAP sensor output voltage reads 5 Volts DC which is the same as the input voltage would indicate that this sensor output is shorted to the input.  What effect will this have on how the truck will runs???  Would like to know.

If the output voltage is 5v you will have a high psi situtation reported to the ecm.  I doubt this would make the revs jump like that.  Iam still mostly concered with the p1689 code.  That specifically means the ecm cannot talk to the vp44.  Unplug the map and see if your truck is better, it will throw a code, but effectively it just runs as if there is 0 boost.  

 

The vp44 can idle on it's own without talking to the ecm.  That is what the idle sense wire is for.  Think of idle as a "closed loop" type situation. as soon as tps input is sensed it will jump out of idle state and the ecm will start to command fueling. 

 

Now if your sensors are shorting to ground etc I could see the ecm getting pissed off and not being able to command fueling.  

anyone know where I can purchase the PSG in the VP44.  Took that sucker out of the truck today and boy was that a pain in the everywhere. 

Can't.  The Psg needs to be calibrated to the pump using a 815 Bosch test bench.

 

 

It's all or nothing in terms of vp44

13 hours ago, Me78569 said:

Can't.  The Psg needs to be calibrated to the pump using a 815 Bosch test bench.

It's all or nothing in terms of vp44

2

 

Takes 3 hours to calibrate and flash a VP44. 

 

 

Edited November 5, 20168 yr by Mopar1973Man

Replaced VP44 but have not gotten the truck running yet.  A difficult job for an old coot.