LS3 dead throttle (drive by wire)

[Yelcamino]

So yesterday I finally have everything attached and ready to go so I turn the key and the LS3 fires right up, rpm goes up for a second or two and then it settles down to a nice idle! Awesome! So I blip the throttle and nothing happens. I try again, still nothing.

Full disclosure - To get the pedal harness through the firewall without creating a huge hole, I cut the connector off. Once all the wires were through the firewall, I shortened the harness (it was about 3' too long) and reattached the connector. Simple enough, red to red, blue to blue, etc.
Because I have a Holley mid-ram intake, the throttle body harness was too short to reach. About two weeks ago I ordered a 12" extension from Lingenfelter thinking I would have it soon. I got tired of waiting so I spliced in wire to make the TB harness long enough to reach the TB. Again, simple enough, red to red, blue to blue, etc.

Naturally my first thoughts are I caused the issue, but after looking around online, a dead throttle pedal seems to happen occasionally. So I bought a scanner and I got two codes (but each one comes up three times).

P0107 – MAP or Baro circuit low input
P0641 – Sensor reference voltage “A” circuit/open

Would anyone happen to have a wire diagram showing what voltage should be on what pin for the throttle body and pedal?

If you have any ideas or suggestions, it would be greatly appreciated.

[TomM]

A little background...

What ECM are you using? Stock tune or what?

What wiring harness?

Are you running a supercharger?

Reason I ask is the baro sensor is typically for a supercharger application...

As to the P0641, sounds like you lost 5 volt reference to a sensor(s). Typically on the sensors pin 1 is the 5v reference. Usually are 1 or 2 circuits with 5v signals.

You don't really need to start your car to check the TB. Just turn to on. Watch the blade, if it responds slightly(indexes itself) then you know it is getting some signal. You can press the accelerator pedal and the blade should respond to input...

If you can't find the 5v reference signal, check all the sensors, each one should have it there. You may have to trace wiring back to ECM.

T,

[Yelcamino]

A little background...

What ECM are you using? Stock tune or what?

What wiring harness?

Are you running a supercharger?

Reason I ask is the baro sensor is typically for a supercharger application...

As to the P0641, sounds like you lost 5 volt reference to a sensor(s). Typically on the sensors pin 1 is the 5v reference. Usually are 1 or 2 circuits with 5v signals.

You don't really need to start your car to check the TB. Just turn to on. Watch the blade, if it responds slightly(indexes itself) then you know it is getting some signal. You can press the accelerator pedal and the blade should respond to input...

If you can't find the 5v reference signal, check all the sensors, each one should have it there. You may have to trace wiring back to ECM.

T,

Tom,

My ECM is the E67 with a stock tune, no supercharger or turbo, GM performance harness. Last night I checked the pins on the TB connector and two of them had 4.8v and the others were 0v. I didn't check the connector at the pedal. I'll do that tonight.

[TomM]

Tom,

My ECM is the E67 with a stock tune, no supercharger or turbo, GM performance harness. Last night I checked the pins on the TB connector and two of them had 4.8v and the others were 0v. I didn't check the connector at the pedal. I'll do that tonight.

Okay cool. The E67 is typically used for supercharged applications, the barometric pressure sensor could be toggled to "no report" so it will not set a code. Explains why it might have not been disabled. Pretty sure you won't have one on the N/A LS3 engine you have.

As to the others you should have received some literature with your engine that has the pin outs included. If not you can down load them off the web, not sure where, but I have seen them before.


T,

[Yelcamino]

Okay cool. The E67 is typically used for supercharged applications, the barometric pressure sensor could be toggled to "no report" so it will not set a code. Explains why it might have not been disabled. Pretty sure you won't have one on the N/A LS3 engine you have.

As to the others you should have received some literature with your engine that has the pin outs included. If not you can down load them off the web, not sure where, but I have seen them before.


T,

I have the paperwork and yes it does give info on the pin outs (color, location and purpose) but it doesn't give voltage values. I'm going to keep digging, can't give up yet!

[cpd004]

The throttle pedal and throttle body need to match. If you're using an E67 ECM, a trailblazer pedal would be required. Are the 2 from the same donor vehicle? otherwise either at the pedal or the throttle body the wire order may have been reversed. Just 2 things that came to mind.

[TomM]

I have the paperwork and yes it does give info on the pin outs (color, location and purpose) but it doesn't give voltage values. I'm going to keep digging, can't give up yet!

I have the pin outs for a 2008 Corvette if you can verify that's what they sent you. Not sure if it's the E67 ECM, but might get you started.

T,

[Yelcamino]

The throttle pedal and throttle body need to match. If you're using an E67 ECM, a trailblazer pedal would be required. Are the 2 from the same donor vehicle? otherwise either at the pedal or the throttle body the wire order may have been reversed. Just 2 things that came to mind.

I'm using the GM Performance Parts kit that included the ECM and pedal, so I assume they match.

[Yelcamino]

I have the pin outs for a 2008 Corvette if you can verify that's what they sent you. Not sure if it's the E67 ECM, but might get you started.

T,

If you would share the pin outs that would be great.

A friend suggested that since I have a code for the MAP, that I unplug the MAP and see if I the throttle works. His reasoning is that the reference voltage is shared by the various sensors and if the MAP is bad and/or grounding, it could stop the pedal from working. It's an easy way to check it so I'll give it a shot after work.

[TomM]

Here you go...this is the actual diagram, with color code.

T,

[Yelcamino]

Here you go...this is the actual diagram, with color code.

T,

Awesome! Thanks! :thumbsup:

[Yelcamino]

Well I fixed it!

When I passed the wires for the gas pedal through the firewall, I shortened them as I mentioned in my opening post.

Each spliced wire got heat shrink around the connection. Once all the connections were made, I slid the metal sheathing down over the spliced bundle. Then I put a single piece of larger heat shrink over the entire bundle to keep the wires together and also to keep the metal sheathing in place.

Apparently when the large outer heat shrink shrunk, it must have shrunk so tight that any sharp points on the connections pushed through the inner heat shrink and made contact with the metal sheathing causing a ground situation (I only figured this out by doing a continuity test on each pin). After I pulled the bundle apart, I wrapped some electrical tape around each one, and suddenly the throttle worked!

Now I need to get back in there and clean things up so this doesn't happen again!

Thank you everyone that replied and offered suggestions and especially TomM for the schematics!

[TomM]

You are welcome any time.


T,