REDUCED ENGINE POWER. Read below and please help me understand this.

[stretchit]

How do I check CAN BUS on my 2005 z71 Tahoe. I understand how to do it through a 16 pin OBD2 port but have no idea how to do it on my Tahoe due to it only having 4 pins in the OBD2 port. Ima supa confused. It has two grounds, data wire, and power wire or voltage wire. Any help on this is much appreciated. Im losing my mind ova here! haha

The reason i need to check this is because I have a major NO THROTTLE RESPONSE issue along with a REDUCED ENGINE POWER message. I have a new throttle body on it. same size as stock. It powers up when i turn the key on and thats it. Codes P0120, P1125, P2120, P2125 are consistent.
Things i have done to fix this issue.
1. checked all wire connections looking for loose ends or damage. I don't see any wire issues but maybe it's super hidden somewhere?
2. Grounds are all clean and tight. I even created a new ground system from the negative terminal to the TAC module, to the Firewall, down to the front side of the head of the engine, to the PCM. Even the "hard to reach grounds on the back of the 5.3" made new ground out of the problem ground ive heard about and cleaned and checked all the wires. Looks good. I have two black grounds that come of the wire harness in the back of the engine. those are good. The only ground i don't have hooked up is the Firewall ground to hood. I doubt that is causing no response from the throttle body. Please correct me if I'm wrong.
3. Tested another TAC and got the same response so im assuming the TAC module is fine.
4. New TPS sensor at the gas pedal was installed. still no response. (it has a pedal adjuster attached to the gas pedal, not sure if that could cause any issues? It currently is not plugged in.)

If anyone can help me understand how to test my new throttle body with a multimeter too that would be awesome. Cant find anything on my year.

Its a fully rebuilt Tahoe. My tuner came over and noticed I had accidentally switched the coil pack plug-ins on the passenger side, he fixed them and the truck started up great. sounded so good! he reved it a couple of times and it sounded awesome, no issues! THEN it happened, turned off the truck, he grabbed the tune kit plugged in and the throttle stopped responding.

Any advice or help on this is greatly appreciated. Its been a week of me trying to fix this issue so I can get my baby rolling again and it hurts my heart so much.

Thank you all for reading and for any future help.

 

[Joseph Garcia]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please.

I cannot personally assist you with your issue, but other members of this Forum much more knowledgeable than me in this area will chime in.

Do you have access to a quality bi-directional scanner, like a Tech 2 or equivalent? I believe that it would greatly assist in troubleshooting this issue.

 

[stretchit]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please.

I cannot personally assist you with your issue, but other members of this Forum much more knowledgeable than me in this area will chime in.

Do you have access to a quality bi-directional scanner, like a Tech 2 or equivalent? I believe that it would greatly assist in troubleshooting this issue.

I do not have one, I just have a Bluedrive OBD2 scanner. I think its time I buy a good scanner. Do you have any recommendations that wont break the bank?
Thank you for replying

 

[Doubeleive]

I do not have one, I just have a Bluedrive OBD2 scanner. I think its time I buy a good scanner. Do you have any recommendations that wont break the bank?
Thank you for replying

what happens if you put the old throttle body back on?

 

[stretchit]

It's in the trash it was in bad shape. Wish I would of kept it.
Going to look into buying a used one and a better scanner to help me trouble shoot.
Using this TB

• 76100

JET Powr-Flo Throttle Bodies 76100​

 

[stretchit]

Just for a update. No solution still and no fix after multiple attempts. Bought a tech II and I love it but doesn't matter cause my issue has to be a stuck PCM. I attempted to reflash the PCM but couldn't. Put another throttle body and TAC with no change. I HAVE CHECKED THE WIRES VERY VERY VERY WELL. IT HAS TO BE THE PCM. Im losing my fking mind with this ****** problem.

 

[stretchit]

ANOTHER UPDATE. All wires have been soldered, New pcm installed, AND STILL NO RESPONSE TO THROTTLE BODY

 

[stretchit]

Guess it's time to hit another forum, no one knows anything about this issues

 

[Doubeleive]

Guess it's time to hit another forum, no one knows anything about this issues

i think you need to go back to the initial problem
"he grabbed the tune kit plugged in and the throttle stopped responding."
you should be able to use the tech2 to check communication for every module in the truck, it should also provide data for you to look at and determine where the problem is.
do some research look at the troubleshooting tree for the throttle body, use a meter check the wires, check ohm's, etc.
while the engine is running and/or while driving around it should show you commanded state of the throttle body

 

[stretchit]

i think you need to go back to the initial problem
"he grabbed the tune kit plugged in and the throttle stopped responding."
you should be able to use the tech2 to check communication for every module in the truck, it should also provide data for you to look at and determine where the problem is.
do some research look at the troubleshooting tree for the throttle body, use a meter check the wires, check ohm's, etc.
while the engine is running and/or while driving around it should show you commanded state of the throttle body

Throttle body is fine. Both throttle bodies are working. Both TAC modules are working. TPS wire pigtail connector has been replaced. Grounds have been cleaned. New battery. Both pedal sensors are working .... I just don't understand this. I have soldered all the wires I orginally crimped.... still no change.
When I turn the truck on the Thorttle body clicks and that's it.
Driving isn't possible and running the engine isn't possible cause it just revs up to 4,000 rpm due to no signal from throttle body. Scanner has not helped me yet. Thinking about just throwing more money at and see what happens. Maybe if I just buy new harness? Idk this is absolutely frustrating

 

[stretchit]

Another update....... all previously crimped wires have been individually soldered. Even moved a back ground thinking it might help lol.
LITTERALLY NOTHING HAS CHANGED. guess it's time to take engine out and replace harness? Who knows at this point. Might look for a donor car to put engine in. F U, GM. Garbage electrical issues. Stupid. Im mad

 

[Doubeleive]

Another update....... all previously crimped wires have been individually soldered. Even moved a back ground thinking it might help lol.
LITTERALLY NOTHING HAS CHANGED. guess it's time to take engine out and replace harness? Who knows at this point. Might look for a donor car to put engine in. F U, GM. Garbage electrical issues. Stupid. Im mad

something doesn't make sense, you tested each wire for ohm's/ground/voltage?
tested each pin between the pcm and throttle body?

 

[stretchit]

something doesn't make sense, you tested each wire for ohm's/ground/voltage?
tested each pin between the pcm and throttle body?

No just visual inspections. Did some research and am now going to check each wire Individually, ohms, voltage, and whatever else. Thanks for the help, I will keep posting updates. Hopefully I can pin point it!

 

[stretchit]

The cable from the pedal sensor to the TAC module has a continuous electrical path. Same for the cable from the TAC module (right side) all the way to the TPS connection. Going to check the other 8 wires coming from that TAC module cable to the fuse box.

 

[stretchit]

The cable from the pedal sensor to the TAC module has a continuous electrical path. Same for the cable from the TAC module (right side) all the way to the TPS connection. Going to check the other 8 wires coming from that TAC module cable to the fuse box.

Just finished checking and I have flow all the way thru to the fuse block. Noticed a little dirt in the fuse box right where the cables connect. Just going to clean it real good and put everything back. If that doesn't change anything I will move on to checking grounds for continuous flow. After that I'll plug the battery back in and check voltage. Then idk lol

 

[stretchit]

Also this is what my OBD port looks like. Thought this truck had a CAN network but im not sure. That's the first thing I wanted to test. Based off the port, I can't test it thru there.

 

[Doubeleive]

Also this is what my OBD port looks like. Thought this truck had a CAN network but im not sure. That's the first thing I wanted to test. Based off the port, I can't test it thru there.
View attachment 428912

follow the harness for the obd port back and see what's up there should be more than 3 wires

 

[stretchit]

follow the harness for the obd port back and see what's up there should be more than 3 wires

It has four wires that I followed and they just tie into the harness then connect I to the driver side fuse box. I guess I should test continuity? Or keep digging. Seems like it should have more then 4 pins/wires in the OBD port

*Red arrow is the 4 wires from the OBD port
*Green arrow is the OBD port

*forgot to mention that the previous owner had a tracker that was spliced Into the ground and voltage wire of the OBD. Took that out but the throttle response issue didn't change

 

[Doubeleive]

you seem to be missing pins 6 & 14 which is can bus high & low, has this thing had a engine swap or anything?

 

[stretchit]

you seem to be missing pins 6 & 14 which is can bus high & low, has this thing had a engine swap or anything?

No not too my knowledge. Its a 5.3 LM7. When I took it apart it looked pretty dirty and stock.

Thanks for letting me know, I felt like I should have those to test it. Not sure what to do now lol thanks again for the help