2004 Tahoe Throttle issue

[Twithers]

I recently bought an '04 Tahoe. I've done alot of preventative maintenance stuff, since I don't know the history. Fuel pump/ sender assembly, oil pump and o-ring, timing chain and gears, rebuilt top end of the motor, and some other little things.

Currently, I have no passing gear when the pedal is floored. The scanner shows that the computer reads the throttle input up to 57%, but nothing more. I assume that there's no passing gear because the computer has no idea that the pedal is past 57%. Is this a throttle position sensor (under the hood) problem or an accelerator pedal position sensor (on the gas pedal) problem? Is it simply a replacement of the problem sensor or is there some sort of calibration involved?

I have an issue with the gas gauge reading backwards (full tank=needle on EMPTY and low fuel warning, needle travels toward FULL as the gas is used up), I haven't figured this one out yet, but I don't think it would have any relation to the lack of a passing gear.

Thoughts?

 

[OR VietVet]

Welcome to the forum. It could be both or either. I replaced both on my 05 even though they were fine at the time but I wanted to take care of it before problems. Your fuel gauge problem was likely caused by the new parts install. Was ok before the fuel pump/sender replacement? Tell me you used a Genuine GM pump/sender assembly.

 

[George B]

Welcome to the forum. It could be both or either. I replaced both on my 05 even though they were fine at the time but I wanted to take care of it before problems. Your fuel gauge problem was likely caused by the new parts install. Was ok before the fuel pump/sender replacement? Tell me you used a Genuine GM pump/sender assembly.

This and was any wiring repair involved with the swap.

 

[Fless]

Flex Fuel or gas? Did you buy the entire fuel pump module (what brand), or have to swap over some components before installing?

Will your scanner graph the PID for the pedal position sensor? For the throttle position sensor?

 

[Twithers]

Welcome to the forum. It could be both or either. I replaced both on my 05 even though they were fine at the time but I wanted to take care of it before problems. Your fuel gauge problem was likely caused by the new parts install. Was ok before the fuel pump/sender replacement? Tell me you used a Genuine GM pump/sender assembly.

Got the pump from the local Chevy dealership. The gauge had been doing the backwards thing prior to me changing out the pump assembly. It did look like the pump had been replaced before. I thought maybe it has something to do with the wiring, but it's only 4 wires. If I remember correctly, blue and purple, and 2 blacks. Not much to go wrong.

 

[George B]

Got the pump from the local Chevy dealership. The gauge had been doing the backwards thing prior to me changing out the pump assembly. It did look like the pump had been replaced before. I thought maybe it has something to do with the wiring, but it's only 4 wires. If I remember correctly, blue and purple, and 2 blacks. Not much to go wrong.

Except to reverese the gauge wires if someone worked on it. Just worth a check.

 

[Twithers]

Flex Fuel or gas? Did you buy the entire fuel pump module (what brand), or have to swap over some components before installing?

Will your scanner graph the PID for the pedal position sensor? For the throttle position sensor?

It's not Flex Fuel. I got the entire pump/sensor assembly from the dealership. The scanner is a Snap-on Solus, but I don't remember which PID it was polling to come up with the percentage of throttle position. I just remember it would climb up to 57% and stay there until I left off the gas and then it would roll back down to zero.

 

[Twithers]

Except to reverese the gauge wires if someone worked on it. Just worth a check.

I thought about somehow swapping the wires for the fuel level signal, but I just replaced the stepper motors, and some bulbs, in my gauges and wasn't sure which of all those wires going into the gauge cluster to swap. Or if it would even work that way. Seems like it would cause another problem to have to figure out.

 

[Twithers]

On that question about the throttle position, I have adjustable pedals and I've been told that the sensor on the gas pedal isn't interchangeable with one from a non-adjustable pedal. Is it a big deal to change that? Is it the whole pedal assembly with the sensor in it, or do I remove and replace the sensor on my pedal?

 

[Fless]

I thought about somehow swapping the wires for the fuel level signal, but I just replaced the stepper motors, and some bulbs, in my gauges and wasn't sure which of all those wires going into the gauge cluster to swap. Or if it would even work that way. Seems like it would cause another problem to have to figure out.

So it's the flat four pin connector, not the square one. I hate that aftermarket connectors don't use color coded wires.

I wouldn't change anything at the cluster unless you can determine if it was swapped there.

This diagram (also attached as a PDF) is from Haynes and shows the wire colors (if it's correct) at the top center of the page. (Others here may be able to provide better diagrams from AllDataDIY or somewhere else.) From that you can see which wires are which at the pump, but I don't know if the lineup equates to how they're in the connector. Might want to peel back the harness to see if perhaps the connector was replaced and wired incorrectly. You could also verify that the level sensor ground is the orange and black at the wiring harness. In case you're wondering, the level sensor wires go back to different connectors on the PCM.

Lastly, also attached is the pinout of the cluster connector. Hope that helps. Let us know what you do and how it goes.

 

[Fless]

One other thing, the wiring near the throttle body is prone to break; inspect the harness from the TB back a foot or so -- or more if you can -- flexing the wires. They can break or get weak underneath the insulation, not obvious at a glance.

 

[Twithers]

So it's the flat four pin connector, not the square one. I hate that aftermarket connectors don't use color coded wires.
View attachment 358073

I wouldn't change anything at the cluster unless you can determine if it was swapped there.

This diagram (also attached as a PDF) is from Haynes and shows the wire colors (if it's correct) at the top center of the page. (Others here may be able to provide better diagrams from AllDataDIY or somewhere else.) From that you can see which wires are which at the pump, but I don't know if the lineup equates to how they're in the connector. Might want to peel back the harness to see if perhaps the connector was replaced and wired incorrectly. You could also verify that the level sensor ground is the orange and black at the wiring harness. In case you're wondering, the level sensor wires go back to different connectors on the PCM.

View attachment 358074



Lastly, also attached is the pinout of the cluster connector. Hope that helps. Let us know what you do and how it goes.

Thanks for that. I really don't want to have to drop the tank again, unless there's no other way. So, hopefully I'll be able to move wires, if necessary, somewhere upstream.

 

[Fless]

On that question about the throttle position, I have adjustable pedals and I've been told that the sensor on the gas pedal isn't interchangeable with one from a non-adjustable pedal. Is it a big deal to change that? Is it the whole pedal assembly with the sensor in it, or do I remove and replace the sensor on my pedal?

Looking at part numbers, I think you're correct in that they're not interchangeable. I didn't see the sensor sold individually for the adjustable pedals but I didn't look all that hard. You may end up changing the whole pedal assy if you can't get the sensor by itself.

 

[OR VietVet]

It will be the whole pedal assembly and when I did my new throttle body, it was recommended that the wiring harness that plugs in to it be changed at the same time and gave me a part number for it.

 

[Tonyrodz]

Are you sure it's not the throttle body itself? I had a very similar issue a few years ago. Took it to a mechanic and it was the throttle body. Swapped it and no more issues.

 

[George B]

It would be good to have a bidirectional scan too to use for diagnosis.

 

[Twithers]

It will be the whole pedal assembly and when I did my new throttle body, it was recommended that the wiring harness that plugs in to it be changed at the same time and gave me a part number for it.

Was yours with adjustable pedals? If so, would you happen to remember the part numbers for it and the harness?

 

[Twithers]

Are you sure it's not the throttle body itself? I had a very similar issue a few years ago. Took it to a mechanic and it was the throttle body. Swapped it and no more issues.

I'm not exactly sure, but other than this, the truck runs really well. The scanner I used is bidirectional and was showing the throttle position percentage. I'm just not sure yet, if that number comes from pedal position or throttle position. I don't mind changing both parts, if it will fix the problem. I'm just not familiar with this particular system.

 

[OR VietVet]

Was yours with adjustable pedals? If so, would you happen to remember the part numbers for it and the harness?

Yes, adjustable pedals. Pedal assembly-19370279

Pigtail-PT2628

Throttle body assembly-12679525

 

[Twithers]

Thanks