Engine/Transmission (1998.5 - 2002) My 2001 popped a code, P1689 any ideas?

[Davcruz]

Yesterday I started my truck after having just shut it down maybe 5 mins prior. It started right up, but it immediatly revved to about 1200 and then right back down to normal idle and the MIL popped on. I freaked out of course, but I was blocking access to the dumpster at the trash collection area so I left and drove the 4 miles back home. The truck felt like it had less power than usual. As soon as I got home I checked for codes and got the typical P1693 and I got a P1689 also.



So that P1689 is a data com error between the VP44 and the ECM I guess. Am I screwed? Is the VP on the way out? Could the LP be hosed and cause this? Any body got any ideas at all?



I do not have a fuel pressure gauge, but I just ordered the Vulcan unit from Genos, so I do not know what kind of pressure I have yet.



Please help. :{ I just bought this truck 3 weeks ago and I am getting the "I told you so" thing from my wife.

 

[JLandry]

David,



Just getting a P1689 DTC alone is not overwhelming evidence of a failed VP44. That code can be caused by a myriad of issues, like a bad electrical connection between the VP44 and the ECM.



The first thing you need to do is verify adequate fuel pressure exists at the VP44 fuel inlet. Since you don't already have a fuel pressure gauge installed, there's a Schroeder fitting at the fuel inlet to the VP44 where a test gauge can be temporarily attached (available from any good auto parts store) to take this measurement. Assuming you have good pressure there when both idling and WOT, then that code alone may be nothing to worry about yet.



But since you sensed lower power, if you haven't already done so since you bought the truck, start by replacing the fuel filter. Also, you might try disconnecting and then reconnecting the wiring harness at the ECM to insure good pin contact (a long shot but worth trying).



Good luck,



John L.

 

[Davcruz]

John, thanks for those tips! I have replaced the filter about 2 weeks ago. I also ordered a Shop Manual, but do not have it yet (back ordered from Genos), where is the ECM on these trucks?

 

[JLandry]

... where is the ECM on these trucks?

The ECM is on the left (driver's) side of the engine (literally on the engine) sort of behind the fuel filter housing. You'll see the connectors plugged into what looks like a rectangular plate on the side of the engine.



Avoid driving that truck until you check the fuel pressure. If by chance you have low fuel pressure from something like the lift pump failing, you don't want to risk destroying the VP44.



Best regards,



John L.

 

[DSeamans]

FYI - Those are the same two codes I threw when I pulled my fuel relay to crank w/out starting. It could be a connection. Clean em all and put fresh dielectric grease on them before you panic too bad.

 

[JLandry]

FYI - Those are the same two codes I threw when I pulled my fuel relay to crank w/out starting. It could be a connection.

That's a VERY good point...



You might want to consider checking and/or replacing the "FUEL PUMP" relay (which powers the VP44, not the lift pump as you might be mislead to believe by the label), and the "ENGINE CONT 1" fuse. Both are located in the PDC (Power Distribution Center) on the driver's side fender in the engine compartment.



BTW, for testing the relay can be swapped with one from something else non-essential... like the horn or wipers, etc.



Regards,



John L.

 

[Davcruz]

EXCELLENT!! I will look into those today, still waiting on my fuel pressure gauge to get here.

 

[Davcruz]

**UPDATE**

My Vulcan fuel pressure gauge showed up from Geno's today, so I went out to test the pressure.

Low and behold when I started the truck I did the 25 second LP run trick and I could hear it churning away and guess what?? THE CEL DID NOT COME ON!

So I hooked up the Vulcan and started it up, still no CEL. Shut it down and started it about 5 times, no CEL. Drove it hard for about 5 miles, no CEL. Got back in the driveway, shut down, start up, no CEL.

Here is what I am seeing for pressure:

IDLE: 11-13 lbs

NORMAL DRIVING: 4-6 lbs

WOT: 1-2 lbs

I have an Airdog FP100 on order and plan to install it soon, but are those pressures low or normal?

 

[JLandry]

... but are those pressures low or normal?

David,



Those pressures are quite low.



It's pretty much accepted that the minimum pressure you should provide at the VP44 is 5 psi. Keep in mind that's the bare minimum. You're not even getting 5psi consistently at cruise... and that's very bad.



I really don't mean to scare you, but at those pressures you *may* have already damaged the VP44. I wouldn't operate that truck until you put that new lift pump on it to get the pressures up and then see how things work out.



EDIT (thought of this after I posted the above): You may want to try replacing your fuel filter again even though you recently changed it. What if you got a really dirty tank of fuel that's plugging up the filter? If you're running biodiesel, maybe you got a bad tank full? Your current lift pump could be the culprit with the low pressure, but changing the fuel filter would help verify it.



Best regards,



John L.

 

[Davcruz]

So possibly the P1689 is my warning indicator that the VP44 may be on the way out? I expect the Airdog Monday, so that is good.

On another note, I noticed a couple of things when I was messing about with the gauge install.

1) There is a big VOID label on the side of the VP44, what the heck could that mean?

2) There is a 2-4 AWG black cable with a ring terminal on each end disconnected and wire tied to other harnesses. The cable appears to run from the drivers side to the pass. side of the engine compartment in front of the engine and through some convoluted tubing. Like I said, it is wire tied off, so somebody removed it on purpose. Any ideas?

 

[GarrettPetersen]

1698 is a comm error between the injection pump and the ecm. I had that happen with my truck when it had the 24v in it due to the comp box. Edge jnew of the problem and directed me to the correct path which was reflash the comp

 

[Davcruz]

Since I can I decided to put a couple of pics of the cable I found here so you would be able to visualize it better. Also the VOID label.

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[Bob Wagner]

I would get rid of that FRAM oil filter ASAP if its not too late

 

[DRuder]

Void tag is seal for tampering with pump wires , wire may be new charging wire for alternator, may be heavier than stock.

 

[tmacc]

My '01 was bucking and hesitating recently and I also pulled a 1689 code. Checked all of the connections. No corrosion, so I took the Comp out of the loop. It seems to be fine, but I wait to see if it starts acting up before I feel it's cured

 

[Davcruz]

I have been lucky I guess. I have not had that code or any code since that day when I posted this thread. I have installed the Airdog system and a permanent fuel pressure gauge since then and have yet to see the pressure below 17 PSI. Truck is running great and still have the Edge hooked up.