Question about 2007 Chevrolet Chevrolet Silverado 1500

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4.8l, 2wd. What are the probable causes of DTC P0121?

Idles around 2500 rpm. Will not idle down. Cleaned throttle body no positive results.

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  • Chevrolet Master
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That's an emissions code. It's sucking in too much air. Start with checking for vacuum leaks, air filter may not be sealed, could be idle air control valve, throttle pos. sensor. Many possibilities. Start with the simple stuff, you usually get it from that. good luck.

Posted on Nov 19, 2015

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Posted on Jan 02, 2017

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2 Answers

How can I fix high idle?


In theory once the desired idle speed is programmed into the management system, in the absence of such faults as air leaks, sticking idle air control valve and suchlike it should be impossible for the idle speed to be much different from the programmed value because the ECU should continue closing down the amount of air bypassing the throttle butterfly until the idle is around the correct value.

I think you need to go back to basics and double-check the work to ensure everything is as it should be. In the absence of mechanical faults and ignoring the possibility of electronic problems a high idle must be caused by too much air entering the engine, either because the idle air control valve is not closing properly or because the throttle butterfly is not closing fully.

It is worth noting air can enter the intake through leaky diaphragms, split vacuum hoses or faulty pcv systems. It is also worth checking the egr valve if fitted.

Jan 24, 2016 | 2006 Chevrolet Cobalt SS

1 Answer

What is a solution to fixing the mass air flow system, with code po121


DTC P0121: Throttle Position (TP) Sensor 1 Performance
Circuit/System Description
The engine control module (ECM) uses the following information to calculate an expected airflow rate:
?€¢
The throttle position (TP)


?€¢
The barometric pressure (BARO)


?€¢
The manifold absolute pressure (MAP)


?€¢
The intake air temperature (IAT)


?€¢
The engine RPM


P0121 The predicted air flow and the predicted MAP combined are outside a calibrated range for more than 3 seconds.
Circuit/System Testing

  1. Inspect for the following conditions:
  2. ?€¢
    Vacuum hoses for splits, kinks, and proper connections as shown on Vehicle Emission Control Information label


    ?€¢
    Inspect thoroughly for any type of leak or restriction


    ?€¢
    Air leaks at throttle body mounting area and intake manifold sealing surfaces


    ?€¢
    Throttle body for dirt, debris, and coking--Refer to Throttle Body Cleaning.

  3. Allow the engine to reach operating temperature. Observe the MAP Sensor Voltage parameter with a scan tool. Voltage should be more than 0.8 volt and less than 4 volts.
  4. ?‡'
    If more than 4 volts or less than 0.8 volt, refer to DTC P0106.

  5. Idle the engine. Observe the MAP Sensor kPa parameter with a scan tool. Increase the engine speed slowly and then back to idle. The MAP sensor kPa should change smoothly and gradually as engine speed is increased and returned to idle.
  6. ?‡'
    If the MAP sensor kPa does not change, refer to DTC P0106.

  7. Take a snapshot of the engine data list while performing the actions listed below. The mass air flow (MAF) sensor g/s should change smoothly and gradually as the engine speed is increased and is returned to idle.
  8. ?€¢
    Idle the engine.


    ?€¢
    Increase the engine speed slowly to 3,000 RPM, then back to idle.


    ?€¢
    Exit from the snapshot and review the data.


    ?€¢
    Observe the Mass Air Flow (MAF) Sensor parameter frame by frame with a scan tool. The MAF sensor g/s should change smoothly and gradually as the engine speed is increased and is returned to idle.


    ?‡'
    If the MAF sensor g/s does not change smoothly and gradually as the engine speed is increased and is returned to idle, refer to DTC P0101 or P1101.

  9. Inspect the throttle body for the following conditions:
?€¢
Loose or damaged throttle blade


?€¢
Broken throttle shaft


?€¢
Any throttle body damage


?‡'
If any of these conditions exist, replace the throttle body assembly.

Jun 20, 2015 | 2008 GMC Sierra 1500 2WD

1 Answer

Correct code P0504?


What Colorado do you have ? 2 wheel or 4 wheel drive ? Sport ,sport LS 3.5L , Z71, Z71 LS. etc. what size engine ? an does it have electronic throttle control ? I have factory service info an it is not showing that code .
DTC P0506

Circuit Description

The throttle actuator control (TAC) motor is controlled by the powertrain control module (PCM). The DC motor located in the throttle body drives the throttle plate. In order to decrease idle speed, the PCM commands the throttle closed reducing air flow into the engine and the idle speed decreases. In order to increase idle speed, the PCM commands the throttle plate open allowing more air to pass the throttle plate. If the actual idle RPM does not match the desired idle RPM within a calibrated time, this DTC sets.

DTC Descriptor

This diagnostic procedure supports the following DTC:
DTC P0506 Idle Speed Low
DTC P0507

Circuit Description

The throttle actuator control (TAC) motor is controlled by the powertrain control module (PCM). The DC motor located in the throttle body drives the throttle plate. In order to decrease idle speed, the PCM commands the throttle closed reducing air flow into the engine and the idle speed decreases. In order to increase idle speed, the PCM commands the throttle plate open allowing more air to pass the throttle plate. If the actual idle RPM does not match the desired idle RPM within a calibrated time, this DTC sets.

DTC Descriptor

This diagnostic procedure supports the following DTC:
DTC P0507 Idle Speed High
Cleaning the throttle body mite take care of it !
Cleaning Cleaning An Electronic Throttle Body Safely

Jan 31, 2015 | 2005 Chevrolet Colorado

1 Answer

Hight idle


Bad idle solenoid. Located on throttle body. It's black. Plugs in to wiring cable. You need a torx bit to remove. It's a cheap and easy fix. Also, get some throttle body cleaner and a tooth brush. Saturate the inside of the throttle body with cleaner and scrub out the black soot. Do this with throttle body in wide open position. Be sure to clean the edges of the butterfly good. They soot up and stick preventing throttle body from closing all the way.

Dec 15, 2014 | 1995 Jeep Wrangler

1 Answer

Truck dies when idling


HI
first I would like to tell you, do this procedure only if the 5th digit of your VIN is C or K.

Description

The engine control module (ECM) learns the idle position of the throttle plate to ensure the correct idle. Anytime the throttle body is cleaned or replaced, the ECM must learn the new throttle position. The idle may be unstable or a DTC may set if the throttle position is not learned.

Conditions for Running the Throttle Learn Procedure

• DTCs P0101, P0102, P0103, P0107, P0108, P0111, P0112, P0113, P0506, and P0507 are not set.

• The engine speed is between 450-4,000 RPM.

• The manifold absolute pressure (MAP) is greater than 5 kPa.

• The mass air flow (MAF) is greater than 2 g/s.

• The ignition 1 voltage is greater than 10 volts.

Throttle Learn

Important: Do NOT perform this procedure if DTCs are set. Refer to Diagnostic Trouble Code

(DTC) List - Vehicle.

1. Start and idle the engine in PARK for 3 minutes.

2. With a scan tool, monitor desired and actual RPM.

3. The ECM will start to learn the new idle cells and Desired RPM should start to decrease.

4. Ignition OFF for 60 seconds.

5. Start and idle the engine in PARK for 3 minutes.

6. After the 3 minute run time the engine should be idling normal.

Important: During the drive cycle the check engine light may come on with idle speed DTCs. If idle speed codes are set, clear codes so the ECM can continue to learn.

* If the engine idle speed has not been learned the vehicle will need to be driven at

speeds above 70 km/h (44 mph) with several decelerations and extended idles.

7. After the drive cycle, the engine should be idling normally.

* If the engine idle speed has not been learned, turn OFF the ignition for 60 seconds

and repeat step 6.
8. Once the engine speed has returned to normal, clear DTCs.
Good Luck

Mar 04, 2014 | 1995 GMC Sierra

1 Answer

Code p1506


P1506 - Idle Air Control (IAC) Overspeed Error This DTC is set when the PCM detects engine idle speed that is greater than the desired rpm.
  • IAC circuit short to GND
  • Damaged IAC valve
Disconnect IAC valve and look for little or no change in engine rpm as an indication of a stuck or damaged valve.
Ford Idle Air Control IAC valve test how to adjust minimum idle speed
Ford Idle Air Control Valve Diagnostics High Idle DTC P1506

Dec 05, 2017 | 2000 Ford Explorer

1 Answer

98 eclipse 2.0 idles high at 2500 rpms an I just replaced the throttle positioning sensor


sounds like you may have a vacuum leak. any air entering engine not passing through the throttle body will cause engine to race. a whistling sound is sometimes a sign of vacuum leak but not always audible. propane is the recommended method finding leak but I find this unreliable. spraying carb cleaner around suspect areas and listening for a rpm change is more successful. just remember carb cleaner is extremely flammable and caution must be used.

Apr 08, 2013 | Cars & Trucks

1 Answer

Hi i have a code reading P0506 for a 06 GMC Envoy XL any recomondations


{: ) DTC P0506 Idle Speed Low
The usual cause is an excessive carbon build-up on the throttle body. If this is the case, I suggest you have your throttle body cleaned and perform an idle relearn procedure using a GM scan tool. The idle relearn or reset procedure is very important, otherwise this code may still remain even after a throttle body clean.
In a similar fashion, if the ECM/PCM (engine control module) of a high mileage vehicle is replaced and/or reprogrammed without performing the Throttle/Idle Learn procedure, 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.
There are other conditions that can also affect or reduce idle speed by increasing engine load like incorrect torque converter clutch (TCC) operation, accessories that require additional torque to operate, restricted exhaust, and mechanical conditions that limit engine speed.

Aug 02, 2011 | 2006 GMC Envoy

1 Answer

2500 to 3000 rpm idle


Change your Thottle positioning Sensor. My 93 lesabre did the same thing and i changed the TPS and it stopped.

Jun 11, 2009 | 1993 Buick LeSabre

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