2006 Tahoe Reduced Engine Power

[2ndserve]

Yesterday I purchased a 2006 Tahoe with 200K for $700 with a known REP problem. The previous owner had used it without problem until very recently. He stated the problem first occurred one recent day when he turned on the AC. REC on the dash, he limped it home, cleared the code...which worked until he tried to use the AC again. A day or two of that frustration and he decided to sell.

When I bought it, I drove it home...with no REP issue. While driving close to home, I too turned on the air and it eventually went REP. Clear the codes...the problem is "fixed"

This morning I played with it a little. Without AC or lights it runs fine, no REP but a couple other seemingly unrelated codes do pop up:
1. p0030 - HO2S Heater Control Circuit (Bank 1 Sensor 1)
2. P0449 evap emmission system vent valve/solenoid circuit:

I then drove it and turned the lights on as I was doing about 35...again, the REP light comes on and I get:
U0107 - Lost Communication with Throttle Actuator Control (TAC) Module

I cleared the codes again and did the same thing at idle and when the REP shows up and I checked codes I get all three above and:
P0120 - TPS A Circuit Malfunction (throttle position sensor)
P0220 - TPS B Circuit Malfunction
P1516 - Throttle Actuator Control Module Throttle Actuator Position Performance

Reading around on the web, I get information that seems close the the problem I'm having but the "fixes" are varied: Bad Gas pedal assembly, Bad Throttle sensor/assembly, moisture shorting wires, damaged wiring, weak battery, bad alternator...and so on.

I'd rather not throw money at parts or start troubleshooting in the wrong direction. If anyone here might be able to make more sense of this then I can and has some pointers in what might be wrong, where to start, I'd greatly appreciate it. Otherwise the Tahoe is in pretty good shape.

I'm thinking about starting by getting the battery and alternator tested but rather not chase irrelevant ghosts. I'd love feedback from folk more knowledgeable then myself.

Thanks in advance!

 

[treehan77]

Start with battery and alternator. Check grounds. From there ? Try known good ecu possibly.

 

[retiredsparky]

I suspect a grounding or 12volt problem as mentioned by Travis. When you turn on the lights, this places an additional load on the grounding system and the 12volt positive. A corroded or loose connector, or a rusty bolt connecting the ground to the frame, body, battery etc can cause strange symptoms and actually damage the many modules that are interconnected in the vehicle.

Voltage levels change when there is a changing load-your many different problems are all related to this one problem. I would install a new ground to the front of the block from the body, check all those power and ground cables.

 

[2ndserve]

I used my multi-meter to check resistance in multiple areas regarding ground and power. all were very negligible (1 ohm at about the most) including from the block to the body. I suppose I may have missed something in testing all that but it sure seemed reasonable.

I should mention, this truck has two batteries...but both tested over 14v with a light and AC on. Disconnected from each other with nothing on, they both read 12.6V or so.

I also checked the wiring connector leading into the Throttle Body Actuator lightly tugging on all the wires...all seemed fine. I didn't actually get inside it, so it's possible their is internal corrosion I missed.

I've read enough on this issue to wonder if it might be the Gas Pedal assembly...as it seems many have had a similar problem solved by replacing it.

 

[jaywoo65]

I've had the P1516 a couple times recently. I just ordered a throttle position sensor from Amazon.

 

[Floep]

Check the ground connectors at the rear of the engine, to the firewall, Hard to see, get good light and tug and shake them.

 

[rockola1971]

Check the battery isolator to be sure it doesnt have diodes going/gone bad and arent loading down your 12vdc. As mentioned before, the rear block to firewall ground remove it and clean or replace (if its corroded bad enough or coming apart). Clean the block connection point and the firewall connection point. I would do this no matter what. It will save you from this headache possibly or future ones.
Have someone in the driveway with the Tahoe in gear turn the a/c and/or the headlights on while you are measuring the primary start battery and it should be lingering well above 12vdc. If it doesnt then you have something loading down the circuit in the load that you turned on. If the ground connection is the problem then all bets are off and there will be no rhyme or reason as to what causes it immediately to go into the REP. No pattern whatsoever.

Anything that lowers your 12vdc bus will cause these headaches and chaos. The PCM uses the 12vdc as signal voltage supply and looks for a certain voltage range coming back. If the voltage signal return coming back isnt above a min for a certain amount of time then it will start throwing codes and suspect a sensor bad even though its just the 12vdc bus getting loaded down.