Needing help with a sporadic p 1689 code. It's the only code I get and it only when I have been driving for a good bit. (Daily 20min drive to work won't trigger it) vp44 is new ish. (2 years may maybe 50k miles) was from DAP and was one with a supposedly rebuilt pump "brain"

I have gone through the really helpful guide on this website. Everything tested good except the step on the ECU. Im shure it could be the ECU but want to rule everything else out. Fuel pressure looked good on the quadzilla ecu voltage looked good tps was steady.

Truck drives fine but will suddenly go through a fit* and cut in and out then be done and drive fine. It has recently started to rev on start up then drop back to idle.

I do have the passenger side battery removed and the ground cable grounded to the fender. (First thing i checked reads 1 ohm to the driver battery negative) the tps is a cheaper Amazon part. But has been reset and set to the proper voltage range properly. And tracks smoothly on the quadzilla so I don't think that's the issue. Really not shure what else to check on this

4 hours ago, yohon said:

I do have the passenger side battery removed and the ground cable grounded to the fender. (First thing i checked reads 1 ohm to the driver battery negative) the tps is a cheaper Amazon part. But has been reset and set to the proper voltage range properly. And tracks smoothly on the quadzilla so I don't think that's the issue. Really not shure what else to check on this

Did you do a W-T ground wire mod? Not good to leave a battery out. I know these trucks will run on a single battery but the passenger side typically is the source of ground for VP44, ECM, and PCM. W-T ground mod would move it to the driver-side ground for the VP44 and ECM but the PCM is still on the passenger cable.

4 hours ago, yohon said:

Needing help with a sporadic p 1689 code. It's the only code I get and it only when I have been driving for a good bit. (Daily 20min drive to work won't trigger it) vp44 is new ish. (2 years may maybe 50k miles) was from DAP and was one with a supposedly rebuilt pump "brain"

No such thing as a rebuild PSG unit. It's either USED or NEW. Sadly rebuild PSG is a poor choice being that it most likely not calibrated to your pump. The other part is Bosch Certified Rebuilt pumps it is a REQUIREMENT to replace the PSG with a new unit and be calibrated on the test stand.

4 hours ago, yohon said:

Truck drives fine but will suddenly go through a fit* and cut in and out then be done and drive fine. It has recently started to rev on start up then drop back to idle.

Most likely a bad solder joint in the repair of the PSG and the heat is causing a solder joint to open up. Yeah, I've seen a ton of people doing transistor replacements and weird home repairs but did they ever calibrate the repaired PSG to the mechanical part of the pump? No. This where problems start.

No W-T mod I wasn't sure if the battery mod was going to be permanent so I kept it pretty reversible. I essentially added a battery post to the inner fender and moved the ground clamp over to that. I may try putting a second battery back in to see if that helps. Or run the ground back to the driver battery ground.

I'll have to call DAP and see but I believe I got a vp44 with a new ecu then. I distinctly rember them suggesting a slightly more expensive pump that they said they had way less returns on.

Other thought could the pump tap wire be causing this? The quadzilla tap is way better they the scotch locks most fokes use but is still a tap.

2 minutes ago, yohon said:

Other thought could the pump tap wire be causing this? The quadzilla tap is way better they the scotch locks most fokes use but is still a tap.

If possible, maybe you could try unhooking the wire tap and see. No need to remove the entire splice, just unhook the wire. I think it's a heat issue on the PSG. By chance, what does the Quadzilla show for fuel temperatures?

I can't say I have checked recently and don't normally have it up 80-90 comes to mind though. I do have a good air dog on it with large line and large draw straw pressure does not drop below 15...unless I'm less then a eighth of and tank and slam on the brakes. ( not a normal occurance)

Depends on the location of the straw for the temperature. Hopefully, your straw is in the main fuel tank and not the sender basket. I'm assuming you are in the main tank area, being the 1/8 tank drop in pressure on hard sloosh. That would net you cooler temperatures in the fuel, being the hot fuel is kept in the sender basket.

Is your warranty still good on the VP44 pump?

Ok yes we are in the main tank for the straw location! Sadly i think not because i couldn't resist pump tapping it. I will call and talk with them to confirm. ( they have been super great in the past went through 5 turbos with them)

You might end up eating that VP44 but just maybe... I'll leave the lights on for ya and just post up.

Well though I had some good ideas for testing. Realized I could just wiggle the pump tap with a bit of throttle applied and see if it cut back to idle (doh) wasn't that.

Did some spirited driving to get things hot had a camaro pull up... I don't like to push my truck it's a great way of breaking it. But today for whatever reason I let it eat and I don't know who was more suprised the camaro or me but man these ol trucks can still run!

Anyways got it got got it home wiggle checked everything messed with pulling that passenger ground nothing even took a heat gun to the vp44 brain and got it a little warmer. Nothing 🙃 ill try calling DAP in the morning and see of they have any ideas. But for now I'm pretty clueless.

2 minutes ago, yohon said:

Did some spirited driving to get things hot had a camaro pull up... I don't like to push my truck it's a great way of breaking it. But today for whatever reason I let it eat and I don't know who was more suprised the camaro or me but man these ol trucks can still run!

My last one was a Ford Pickup, and I laid waste to him at about 110 MPH running Beast. Yeah, these trucks can run and really pull like a mule. Beast I just tucked in the garage today for his long nap. Beast can sometimes fry the tires just by accelerating up to highway speeds, like getting up to 80 to 85 MPH for I-84 here in southern Idaho.

5 minutes ago, yohon said:

Anyways got it got got it home wiggle checked everything messed with pulling that passenger ground nothing even took a heat gun to the vp44 brain and got it a little warmer.

Now I'll tell you engine heat will not affect the PSG. If you take a look at...

The top lid has an air space between the top and the PSG circuit board. The PSG circuit board is actually heatsinked to the fuel side, hence why I asked about the fuel temperature being high. Fuel temperatures will be hard on the PSG, and also the fuel being above 140℉ or 150℉, you'll see your fuel filter plug up faster with asphaltenes.

Well that was smart of Bosh. I will pull up fuel temps and see what I'm getting to but I don't think it's anywhere near that high. I just wish I could get this to be consistent. It's been off and on for probably 6 months.

4 minutes ago, yohon said:

It's been off and on for probably 6 months.

My adventure with Thor was similar. I was having injector issues. Just got to make the first step and call and see what @dieselautopower can do for you.

Will call tomorrow at lunch and see what they can do. Found someone posting about the start up rev issue in a different fourm and had the same 1689 code they traced it to the data link conection on the comp. I'll check into that and see what's what.

Try unhooking the Quadzilla CANBus lead. See if the Quadzilla causing the CANBus to fail.

Another to check the fuel pump relay it could cause this P1689 bad power contacts.

OK so update time! Talked with Mitchell from DAP today at lunch very helpful! Vp44 i got had a new brain (PSG) rebuilt pump with a 2 year warranty but I bought it in 2022 so 3 years (man time flies) he did give me some insight on my problem

Could be caused by intermittent failure of APPS and would be faster the the quad could pick up/display

Didn't think it could be caused by intermittent lift pump relay if I was still seeing steady pressure.

Possibly could be quadzilla connections to data link so I wanted to check that first (cheepest easiest thing first!) I'm not shure if this is the smoking gun but to me it is questionable.

The middle socket is recessed/pushed in about 1/8th more then then outer 2 pins And on this conection (rather hard to see with all the dielectric grease in the way) it would appear as though the right most connector doesn't have the sping side of the pin

everything passed the wiggle test at 1200 rpm though so not shure if it's worth re pinning either of these. I do have my father's 2001 24v sitting in the driveway for the forciable future and I already talked to him about using his APPS for troubleshooting so next good long trip I get I'll try and swap them out and see if I still have the issue. Did get get a good check on fuel temps 87 on the drive in 97 on the way back about 85 degrees ambient so not bad.

Fuel pump relay is in the PDC which controls power the the VP44 injection pump. Yes a bad relay will set a P1689 code if the relay is bad or no power given to the VP44.

Well then the glove box relay is going in lol.

Well I think it was just timing but i put the lift pump relay in this morning. On the drive home I noted the check engine light was out. I'll try and go on some longer drives this weekend and see if it comes back.. feel like it's not gone for long...

Not lift pump relay the Vp44 relay.

I always thought that was for the lift pump. Glad you said that. I swapped the vp44 relay for the wiper motor relay and so far the code has stayed cleared only had about 2 longer trips but fingers crossed that was it.