Engine/Transmission (1998.5 - 2002) No voltage to TPPS

[SMalafy]

I tried adjusting my throttle position sensor but can not find any voltage whatsoever ! I also have 4 DTC codes and am not sure if it has anything to do with it. P-1693 JTEC module ( don't know what the JT stands for)
P-0122 which I was trying to adjust but no voltage. P-0602 ECM fueling calibration ( I need to take the air bubbles out of the line running to my fuel pressure gauge and squirt some more antifreeze in the line) and P-0230 lift pump out of range but I am running an Air Dog raptor and the pressure is supposed to be 17 psi.
The truck runs and shifts fine but the mileage is off by a few mpg's and now my newly installed Pacbrake quit working too so I guess it has to do with the codes.

 

[Ozymandias]

TPS can't be adjusted, more then likely it is just broken as it is a wear item.
Thats also the reason why the Pac doesn't work anymore.

Get the Timbo TPS from Genos.

 

[SMalafy]

TPS can't be adjusted, more then likely it is just broken as it is a wear item.
Thats also the reason why the Pac doesn't work anymore.

Get the Timbo TPS from Genos.

Well why is there no voltage coming out of the plug that plugs into it ? Should I not have some kind of voltage coming to the plug disconnected from the sensor with the key on ?

 

[BigPapa]

I can’t find anywhere it specifically says that it should be 5V, but the “Sensor Supply” is on pin 5. In the description of the ECM, it says the ECM Outputs are:

 

[SMalafy]

Yes I hit all the pins and there was no voltage. Its supposed to be 5.68 or something like that. I am sure I probed the dark blue / white striped wire and nothing. I should have something.

 

[Ozymandias]

Well you say it runs and drives fine - so there must be voltage right?

 

[SMalafy]

When I could not find voltage with it plugged in the sensor I disconnected the sensor and probed the plug itself and got no reading whatsoever. I would think I should get something. Going back to your first reply you said that the sensor does not need adjustment but there are plenty of videos on youtube showing how to adjust it. Thats why the holes for the screws are oblong for the adjustment.

 

[BigPapa]

From the Service Manual:

 

[SMalafy]

Then why are there so many videos on Youtube showing replacement of just the sensor box and then adjusting it with success or just adjusting the one you have ?

 

[BigPapa]

I don’t know. My experience is with the 2nd Gen 12-valves. I’m just trying to help with diagrams and what the manual says.

 

[petersonj]

I think (remember, I said, "I think") that the 12 valve engine only uses an APPS for automatic transmission control.

On the 24 valve VP44 trucks, the APPS is interfaced with the ECM only. There is an idle validation switch inside the APPS to tell the ECM when to idle the engine. So, on the VP44 trucks, there is an adjustment that puts the APPS signal value below a certain voltage threshold, which in turn tells the ECM to take over and idle the engine.

- John

 

[gtwitch]

I am trying to find the wire from the ECM that powers the fuel lift pump. The lift pump ( in my case is located on the frame along with a fuel filter at the output of the pump) I get no pump running at any time with key on or in the start mode and my fuel pressure gauge has no indication. This all went away when I replaced the MAPS sensor. When I replaced the Carter lift pump 20 years ago I put a Holly Blue 15 psi lift pump on the frame ahead of the tank and below the level of the fuel so there is always no air in the pickup side of the pump, I wired that to the wire that went from the ECM to the Carter pump that was on the block above the starter and this has worked fine for over 20 years. I cycled the Holly pump with 12 volts and pump is fine but no volts coming from the ECM at this time. Is there a fuse or relay in the power control center on that circuit ??? Any ideas here ?? Is this voltage from the ECM also controlling the APPS and /or the VP 44. gtwitch in wyoming

 

[petersonj]

I wired that to the wire that went from the ECM to the Carter pump that was on the block above the starter and this has worked fine for over 20 years.

In stock form, the lift pump is powered directly from the ECM, terminal #15 and #35 (both a YL/WT wire). Both wires go to Splice #160 and continue as one YL/WT wire to the lift pump. Normal operation is when key is turned to "Run" position the lift pump runs for 1/4 second, when key is turned to "bump start" the lift pump runs for approximately 25 seconds. There is no fuse specifically for the lift pump.

It has been a common practice to add a relay to the lift pump circuit. This will remove the heavy electrical load from the ECM. The YL/WT wire wire will connect to the coil terminal on the relay which reduces the electrical load on the ECM to about 150 milli-amps.

- John

 

[Topzide]

It seems that a pump that is added using existing power wire, burns up the ECM circuit! I much prefer wiring in relays for the power load. Vehicle wiring isn't made to have heavier loads placed on them, they're designed with the minimum wire gauge possible for their "factory" loads. This helps with tracing down problems as the relay provides an audible click to verify power to relay. Hope that you're not fighting an ECM circuit "burn up".

 

[gtwitch]

This is just what I think has happened, so I will again take the stock fuel filter off so I can get to the wiring that comes to the former location of the Carter pump where I tied on an extension wire to go to the now on frame location of the Holly Blue pump. If I find a problem with that extension wire and find any voltage from the ECM I'll go on from there , but if there is no voltage there , then it is time to have the ECM repaired. A relay will also go in the system at that time. Does anyone think that there might be a used ECM out there somewhere for a 1999 to 2001 5.9??
gtwitch in wyoming

 

[petersonj]

A lot of people have had good experiences with:

Auto Computer Specialists
Physical Address: 221 S State Rd 7, Plantation, Florida, 33317

Phone Number: (954) 513-8359

- John