[BRK04CTS]

Started the car in the morning as usual to warm up. Came back 5 or so minutes later and saw my check engine light was on, service engine soon on DIC. Drive about two miles, got on the main road to about 25mph and then no Acceleration And RPMs wouldn’t go over 3k. Turned around and drove home. When I put the car in park, the RPMs went wild from its normal idle to 1200 jumping up to 2000 and back down. It did this several times so shut the engine off. I feel like I’ve thoroughly combed through the P 2176 code posts. Throttle body position relearn not done. I did the throttlebody relearn Procedure.
*️⃣ Turn the ignition to the on position for three minutes, turned it off, started the car for 30 seconds, shut the car off, then started it and let it run for about five minutes.
⬆⬆⬆⬆⬆⬆⬆⬆⬆⬆
(Is this the proper procedure?)

Seemed a little rough in the beginning but leveled itself out. Drove for five minutes and went right back to square one. I found two vacuum leaks, possibly played a role in the rough idle? I’m going to check the accelerator ignition pedal sensor for voltage next and trace it to the ECM. Is there anything I’m missing or overlooked?

 

[RyanY]

Hard to know exactly what is going on without full diagnostics. However I would start simple by fixing the vacuum leaks and cleaning the throttle body. Next I would remove the neg battery cable, unplug the throttle body connector and apply dielectric grease to the terminals, then reconnect the throttle body and battery. Start the car and see whether the code reappears. If still bad you will need further diagnostics.

 

[Team ZR-1]

On some GM models the TPS relearn is done by key on, engine off, remove the wiring connector from the TB
leave off for like 1 minute
This causes the PCM to trip a TPS DTC and then sets TB butterfly as being zero percent angle
Turn key off, connect wiring connector
Key back on and clear DTCs

IF that is your relearn process and the problem was just that then all would be back to normal

GM is touchy as to drive by wire and if PCM thinks there is some problem it will force PCM into LIMP mode which limits low vehicle speed just enough to limp vehicle to home, repair shop.

PCM monitors in part for vacuum and MAP issues using MAP sensor as example at idle PCM is looking for MAP value about 35 KPA (depending on location to sealevel)

If there is a leak then instead the value could be like 55 KPA but TAC (DBW controller) says TPS angle is maybe 7%
Where 55 KPA though engine would assume driving down the road so since TPS and MAP do not agree with the PCM mapping then trips into fault mode So leaks can cause your problem

TAC is looking at TPS position angle and APP (gas pedal) and is doing compares to the 2 or 3 pots the gas pedal has,
IF they and TPS do not agree then PCM goes to limp mode

Really a easy pinpoint using a OBD-II scanner, I give an example below with a Caddy vehicle

With key ON, engine off, watch the TPS angle PID values so not on gas pedal maybe reports 2-7% angle
slowly step on gas pedal and watch to see the values go up smoothly and not jump around
Then slowly back off on gas pedal and watch the same PID and see if those values smoothly come down

IF not the TB problem, then look at the APP PIDs and see if they report proper compares
With engine at idle, does TPS angle look correct, is MAP reporting about 35 KPA
If not then a leak still exists

Other maybes
1. TPS sensor is faulty
2. Some engine vacuum leak
3. TB is clogged up
4. dirty wiring pins of TB or the wiring connector to it
5. bad MAP sensor
6. Problem with APP
7. wiring problem to any of those sensors
8. Worse case the TAC in PCM went bad (unless a older model when TAC was its own controller)

 

[BRK04CTS]

Sure enough on the backside of the Intake manifold, I find this beauty of a patch job. They must have thought those zip ties had Hercules strength and sealed up nice and tight. Just went ahead and replace the whole vacuum hose assembly. I’m not a fan of this Factory GM hard plastic Vacuum hose. It’s brittle, cracked all over the place.

The TB connector. When I originally cleaned the TB I noticed electrical tape behind the connector and thought nothing of it. While chasing down wires, decided to have a closer look. And would ya guess what I found? The previous owner/Mechanic or whoever worked on it prior to me did some JANKY repair. 2 wires exposed, and a 3rd on its way. Individually wrapped in tape then taped over all 6. 🤦🏻‍♂️I just don’t understand why not do it right the firs time. Then again everyone isn’t the same. New Connector ordered,

 

[RyanY]

People do all kinds of half-assed repairs just to get the car back on the road...especially if they plan to sell it!

 

[BRK04CTS]

at this point when I’m finished repairing it and get it all started up again, if it doesn’t run well again I’m washing my hands of it. To be completely honest with you I like the car but I should’ve got the CTSV

 

[RyanY]

at this point when I’m finished repairing it and get it all started up again, if it doesn’t run well again I’m washing my hands of it. To be completely honest with you I like the car but I should’ve got the CTSV

LOL I think we have all said that at one point or another! I also wish I had a V but can't really justify the extra $$$ at this point in my life! In other words, I can't convince my wife that I need the extra speed

 

[BRK04CTS]

I haven’t said up until recently. Just seems like it’s one thing after another. Which is understandable I mean it is a 2004, it does have high mileage, so it comes with the territory. At this point I really don’t want to get rid of it just because of the amount of time and money that’s going into it. Might as well just cover it and find something else to mess with.

 

[RyanY]

I also did a lot of work on my 07 over the past few years. New shocks, struts, sway bar links/bushings, brakes, wheel bearings, timing chains, radiator, etc. Plus all the regular maintenance stuff. Still much cheaper than a newer car unless I add up the hours and calculate wages. Not sure whether it was worth all the effort, but no going back at this point...