Reduced engine power?

Welcome to 2CarPros.

I would try to clean the throttle bore it helps fix these problems, then clear codes

https://www.2carpros.com/articles/throttle-actuator-service

Lets look at what each code is indicating and then see if there is a common denominator between all.

DTC P0171
- Fuel Trim System Lean Bank 1
DTC P0175
- Fuel Trim System Rich Bank 2
DTC P0220 The TP sensor 2 voltage is less than 0.25 volt or more than 4.59 volts for more than 1 second.
DTC P1516 - Throttle Actuator Control (TAC) Module Throttle Actuator Position Performance
DTC P2135 - Throttle Position (TP) Sensor 1-2 Correlation

As you can see, they are all fuel related. There is a good chance the throttle body itself needs replaced. However, before jumping to that conclusion, I need you to check for a couple things. Since one bank is lean and the other is rich, check to see if there are any exhaust leaks before the catalytic converters. It doesn't have to be loud. It can sound like a ticking, especially when cold.

Next, follow this link and check for other vacuum leaks.

https://.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Next, if I had to guess, I would say there is a short to power between throttle position sensor one and two. I need you to check the wiring at the throttle body. Make sure it is not damaged, the connections are clean, tight, and internally not damaged, and make sure there are no cuts in the wiring insulation.

If I recall, this throttle body isn't serviceable. If you are comfortable with testing the electrical end of the system, let me know. I have flow charts (which are quite extensive) I will send. I am not going to overwhelm you with them if you don't want them

I attached a picture of the throttle body. That is where i need the wiring checked. Also, I circled an o-ring that can cause a leak, so make sure to check around there for issues.

Let me know what you find.

Joe

Hi and welcome to 2CarPros. Just wanted to jump in and help out. If you have a K&N filter chances are the mass air flown sensor is contaminated and needs replacing. But for the the throttle codes do this. Remove the throttle body without disconnecting the connector. Clean out the throttle body front and back. This should take care of the idle issue. Here is a bulletin on P1516. 99% of the time in my experience cleaning the throttle takes care of this fault.

Collision

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2007 Chevy Truck Silverado 1500 4WD

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V8-5.3L

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SES Light, Idle Surge, and/or Reduced Engine Power Mode with DTCs P0068, P0121, P0506, P0507, P1516, P2101, P2119, and/or P2176 - Clean Throttle Body and Perform Idle Learn Reset

Vehicle Powertrain Management Technical Service Bulletins SES Light, Idle Surge, and/or Reduced Engine Power Mode with DTCs P0068, P0121, P0506, P0507, P1516, P2101, P2119, and/or P2176 - Clean Throttle Body and Perform Idle Learn Reset

SES LIGHT, IDLE SURGE, AND/OR REDUCED ENGINE POWER MODE WITH DTCS P0068, P0121, P0506, P0507, P1516, P2101, P2119, AND/OR P2176 - CLEAN THROTTLE BODY AND PERFORM IDLE LEARN RESET

#PIP4578B: SES Light Idle Surge And/Or Reduced Engine Power Mode With DTCs P0068 P0121 P0506 P0507 P1516 P2101 P2119 And/Or P2176 - Clean Throttle Body And Perform Idle Learn Reset - (Dec 18, 2017)

Subject: SES Light, Idle Surge, and/or Reduced Engine Power Mode with DTCs P0068, P0121, P0506, P0507, P1516, P2101, P2119, and/or P2176 - Clean Throttle Body and Perform Idle Learn ResetModels: 2007 Buick Rainier2007†2018 Cadillac CTS-V, 2007†2018 Cadillac Escalade2006†2014 Chevrolet Avalanche2010†2018 Chevrolet Camaro2006†2018 Chevrolet Corvette2008†2009 Chevrolet Colorado2006†2017 Chevrolet Express2006†2009 Chevrolet Impala2006†2009 Chevrolet Monte Carlo2006†2018 Chevrolet Silverado2006†2018 Chevrolet Suburban2006†2018 Chevrolet Tahoe2006†2009 Chevrolet Trail Blazer2008†2009 GMC Canyon2006†2009 GMC Envoy2006†2017 GMC Savana2006†2018 GMC Sierra2006†2018 GMC Yukon2007†2008 Hummer H22008†2009 Hummer H32007†2008 Pontiac Grand Prix2008†2009 Pontiac G82006†2009 Saab 97xWith a V8 Engine

This PI was superseded to update model years. Please discard PIP4578A.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:As carbon builds up in the throttle body of a high mileage vehicle, the ECM/PCM learns to compensate by increasing the throttle plate angle.

If enough carbon builds up, an idle surge, deceleration surge, tip-in hesitation, reduced engine power mode, and/or DTCs P0068, P0121, P1516, P2101, P2119, and/or P2176 may be experienced on high mileage vehicles.

If the throttle body is cleaned without performing an "idle learn reset/reset idle learn" with the Tech 2, the ECM/PCM may continue to compensate for previous carbon build up, causing it to return with a similar concern as well as DTCs P0121, P0506, and/or P0507.

In a similar fashion, if the ECM/PCM of a high mileage vehicle is replaced and/or reprogrammed without performing the Throttle/Idle Learn outlined in SI, the ECM/PCM may no longer compensate for existing carbon build up in the throttle body, causing it to return with a similar concern as well as DTCs P0121, P0506, and/or P0507.

If SI diagnosis does not isolate the cause of this concern, inspect the throttle body bore and plate for obvious carbon build up.

If carbon is present, follow the Throttle Body Cleaning Procedure in SI to clean the throttle body.

After ensuring that the throttle body bore and plate are clean, perform an "idle learn reset/reset idle learn" with the Tech 2 and re-evaluate the concern.

Notice:Â Depending on the vehicle you are working on, the "idle learn reset/reset idle learn" is normally found on the Tech 2 ECM menu for Module Set Up or Special Functions/TACÂ System.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

Now the reason I say do not unplug the throttle is if you unplug it and clean it the idle will be really high and the only way to bring it back down is to do a software update. For the running rich most likely the mass air flow is faulty and I recommend you replace it with an A/C Delco part. But clean the throttle body first. Reset the codes and let us know after a 100 miles if the fuel trim faults return.

Hello and welcome back. You should still inspect the throttle bore. If you do not drive much you may have carbon build up. Inspect it and clean it if is dirty. To reset the trim I would recommend you disconnect both battery cables and touch the leads together to do a "reboot" of the computer after you clean the throttle.

We need the code

it is a fly by wire issue with either the throttle body failing or the pedal sensor has failed

Roy

You need to have the computer scanned to identify what is causing this. Most parts stores will do it for free.

Good morning.

P1125
Item Description
Symptom/DTC P1125
Descriptor
Probable Causes
Accelerator Pedal Position (APP) Sensor
Throttle Actuator Control (TAC) Module

This sounds like the engine is going into limp mode due to a dirty throttle body here is a guide to help fix it.

https://www.2carpros.com/articles/throttle-actuator-service

and

https://www.2carpros.com/articles/reduced-power-limp-mode

Please run down these guides and report back.

Good to hear, please use 2CarPros anytime we are here to help.

Roy

There is a problem with the fly by wire unit. It could be the throttle body unit that is bad or the pedal sensor that contains the TAC module. Get a shop to check the unit with a scan tool to verify and give you a bid.

Roy

Check the fuel pump pressure. Watch for the pressure to drop off when it stalls.

Good morning.

The 1518 revolves around voltage issues. I would double check the battery voltage when at rest. It should be 12.6. New battery or not, it needs to be checked.

Then you need to check the charging system. It needs to be 14 to 14.5 volts while running. Also, check for any AC volts while running s well. There should be none.

It could be when the headlights are on, it creates a load and that voltage may be triggering the code.

Roy

CIRCUIT DESCRIPTION
The throttle actuator control (TAC) module and the powertrain control module (PCM) communicate via a dedicated serial data circuit. This serial data circuit is separate from any other serial data circuit on the vehicle. Accurate transmitting and receiving of serial data requires not only good circuit integrity but also adequate system voltage. This diagnostic test monitors the accuracy of the serial data transmitted between the TAC module and the PCM. If the PCM detects a loss of data or invalid data, this DTC sets.

CONDITIONS FOR RUNNING THE DTC
- The ignition switch is in the crank or run position.
- The ignition voltage is more than 5.23 volts.

CONDITIONS FOR SETTING THE DTC
- Invalid or missing serial data messages are detected for a predetermined amount of time.
- The above condition is met for more than 1 second.

ACTION TAKEN WHEN THE DTC SETS
- The PCM illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
- The PCM records the operating conditions at the time the diagnostic fails. The PCM stores this information in the Freeze Frame and/or the Failure Records.
- The PCM commands the TAC system to operate in the Reduced Engine Power mode.

OR

- Under certain conditions the PCM commands the engine OFF.
- The message center displays Reduced Engine Power.

CONDITIONS FOR CLEARING THE MIL/DTC
- The PCM turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
- A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
- A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
- Clear the MIL and the DTC with a scan tool.

DIAGNOSTIC AIDS
- DTC P1518 sets if the battery voltage is low. If the customer's concern is slow cranking or no crank because battery voltage is low, ignore DTC P1518. Clear any DTCs from memory that may have set from the low battery voltage condition.
- DTC P1518 sets when there is a short to B+ on the TAC module ground circuit. Inspect the fuses for the circuits that are in the TAC module harness-i.E. Cruise, brake. An inspection of the fuses may lead you to the circuit that is shorted to the TAC module ground circuit.
- DTC P1518 sets if the TAC module ignition feed circuit is shorted to a B+ supply circuit. The TAC module stays powered-up when the ignition switch is turned OFF. When the ignition switch is turned ON, the TAC module is powered-up before the PCM. DTC P1518 sets because no communication is detected by the TAC module from the PCM. Inspect related circuits for being shorted to a B+ supply circuit.
- Inspect the TAC module power and ground circuits and the TAC module/PCM serial data circuits for intermittent connections.
- Inspect the TAC module connectors for signs of water intrusion. If water intrusion occurs, multiple DTCs may set without any circuit or component conditions found during diagnostic testing.
- When the TAC module detects a problem within the TAC system, more than 1 TAC system related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing an individual condition may correct more than 1 DTC. Remember this if you review the stored information in Capture Info.
- For an intermittent condition, refer to Intermittent Conditions. See: Computers and Control Systems > Initial Insp

Sounds like you have a bad ground to the headlights there is a ground splice pack usually up by the headlights.