P0121 chevy cobalt

This can happen for multiple reasons and a mechanic needs to diagnose the specific cause for this code to be triggered in your situation. Our certified mobile mechanics can come to your home or office to perform the Check Engine Light diagnostic. The ECM turns the Check Engine Light on and goes into a failsafe mode by cutting current to the throttle actuator to put the throttle valve to approximately less than 6 degrees opening. Note : The symptoms are determined by the manufacturer failsafe ECM strategy for the vehicle during a failure and may vary between manufacturers and vehicles.

Scanning and documenting the codes received and viewing the freeze frame data to see when the P code was set. Comparing the data between TPS circuit A and B on the scanner and if incorrect, performing the TPS pinpoint tests as per the manufacturer's recommendations.

The P code will cause the engine ECM to go into a failsafe mode, which will cause various drive complaints until repairs are done like lack of acceleration, high idle, bucking or jerking, limited speeds, or stalling, depending on manufacturer failsafe mode strategy. The P code may be accompanied by other TPS codes, so other repairs may need to be followed up with in order to have a complete fix.

Most failures for code P are for a defective TPS sensor not tracking the throttle angle correctly.

OBD 2 Code P0121

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at With YourMechanic you can skip the auto shop altogether. They send certified and screened mechanics straight to your door and enable you to save big on car repair and maintenance.

Cost of diagnosing the P code. No more waiting rooms! Our mechanics will come to you to diagnose and fix the P code. Recent Check Engine Light is on Inspection reviews. Excellent Rating.

Average Rating 4. Number of Reviews 5, Rating Summary. Johnathon 8 years of experience. Request Johnathon. Johnathon was on time and was very knowledgeable. Going to use in future. Travis 12 years of experience. Request Travis. Fair, honest, punctual, and knowledgeable.

I was also to get back up and running for less than I thought. I have a new mechanic now to recommend to my friends.Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector's pins.

What does this mean?

P0449 Chevy Cobalt

The auto repair labor rates vary widely across the country, and even within the same city. If the Powertrain Control Module PCM detects the calibrated amount of air flow and engine run time have been met, and the Engine Coolant Temperature ECT has not met the minimum thermostat regulating temperature, the code P will set. This input is used by the Powertrain Control Module PCM for engine control and as an enabling criteria for some diagnosis. The air flow coming into the engine is accumulated and used to determine if the vehicle has been driven within the conditions that would allow the engine coolant to heat up normally to the thermostat regulating temperature.

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If the coolant temperature does not increase normally or does not reach the regulating temperature of the thermostat, the diagnostic that use ECT as enabling criteria may not run when expected. Get Access to Factory Service Manuals.

p0121 chevy cobalt

Related Information. Repair Importance Level: 3. Why is the Engine Light ON?A very common issue with the Chevy Cobalt is the P code. P deals with the evaporative emissions control system. It often appears with, or is related other codes, such as PPand very often P P is normally not an immediate threat to the drive-ability of your Cobalt. Also, a really good scanner will help you identify whether or not the valve is operating correctly.

Most shops have them. Otherwise, this article is meant to show how you can diagnose the problem yourself. This means that regardless of which make or model of vehicle, the code will mean the same thing Cobalt or not, as long as it was manufactured after P indicates that the valve or solenoid circuit that controls the evaporation system is not functioning properly.

The EVAP system cycles fuel vapor from the gas tank into the intake manifold, a charcoal canister, or directly into the air depending on the model of vehicle. When this system malfunctions, the fuel vapor is not being dealt with properly. The ECM Engine Control Module of the vehicle has detected that there is a fault in the circuit which controls the vent that releases the fuel vapor from the system.

This will be followed by the service engine soon light. P code will typically not be accompanied by any noticeable symptoms other than the smell of gas and the service engine soon light.

You may notice the slightest dip in fuel economy as well. The EVAP system deals directly with fuel vapors. There are many things that can cause the P trouble code to trigger in your Chevy Cobalt.

Here are the most common problems that will throw the code along with a great video on the whole process:. A mechanic has a wide range of instruments at his or her disposal to diagnose what would be causing the P in your Chevy Cobalt.

Here are the most common things that are done to diagnose the code:. Still having trouble? Of all the items listed above, it would be wise to start with the gas cap and work your way to the fuel tank, since the gas cap is far and away the easiest and least expensive items to replace on here. Good luck figuring out what is causing your Chevy Cobalt to throw the P code.

We hope this helps. If there is anything that you feel like you could add, please feel free to leave a comment below.

p0121 chevy cobalt

You could have a fuel leak. Pay extra attention to your tank level and make sure you are not leaking fuel. Chevy Cobalt P OBDII Code Symptoms The service engine soon light is often the only sign that the P code has been triggered P code will typically not be accompanied by any noticeable symptoms other than the smell of gas and the service engine soon light.

You should particularly notice the smell of fuel around the fuel tank area or fuel filler tube. Here are the most common problems that will throw the code along with a great video on the whole process: Fuel Cap — A bad fuel cap can cause the code to be thrown for sure. If you are getting that message, plus a P, it may save you a ton of time and money to replace the fuel cap and see if it goes away.

This will cause the P code. Look for either a tear or hole in it. This is one of the most common issues that causes the code. Vapor Canister Purge Valve — One of the most common causes of the P code is the vapor canister purge valve. There are a few clips that you need to find and remove. Fuel Tank Sending Unit — It is possible for the gasket that attaches the fuel sending unit to the gas tank to go bad. This can reduce tank pressure and throw the code.

Fuel Filler Neck — There is often a gasket where the fuel filler neck connects with the gas tank. This gasket can dry out, especially with vehicles that spend their time in dry climates.When code P is triggered, your ECM will go into failsafe mode.

Depending on the failsafe strategy of your car, this could lead to limited speeds or acceleration. This problem can also cause intermittent knocking and even stalling for your vehicle. In some cases, the car will not be capable of driving to the shop and will need to be towed. Replacing the TPS or throttle body without attempting a throttle body cleaning.

P0121 – Meaning, Causes, Symptoms, & Fixes

For error code P, one or more of the below repairs may be needed to solve the underlying issue. For each possible repair, the estimated cost of repair includes the cost of the relevant parts and the cost of labor required to make the repair. The Regal was from a friend who wanted to sell it to me at a good KBB price. Thanks FIXD! My check engine light keeps coming on after replacing throttle position sensor. Should I clean throttle body?

p0121 chevy cobalt

Please help. My jeep runs pretty good only thing is I get a lighting bolt sometimes and the engine light is still on I put a brand new motor in it. My Dodge ram I changed plugs still got a skip that it barley moves stalling out how to get it out of safe mode.

Hi, I have a GMC 5. If I have a full gas tank no engine light on. Fill up and it goes away? I have no loss of power, no black smoke blowing out or any kind of a shifting problem? I have no problem with the truck at all but the light coming on with a shorter tank of gas?

New gas cap?? I also have a GMC 5. Wow, I guess this is common on the Gmc Yukon.Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector's pins. Replacing the Throttle Body should take care of the code. What does this mean? The auto repair labor rates vary widely across the country, and even within the same city. Malfunction is detected when an excessively low or high voltage from the sensor is sent to ECM.

This sensor is a kind of potentiometer which transforms the throttle position into output voltage, and emits the voltage signal to the Engine Control Module ECM. In addition, the sensor detects the opening and closing speed of the throttle valve and feeds the voltage signal to the ECM.

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Idle position of the throttle valve is determined by the ECM receiving the signal from the throttle position sensor. This sensor controls engine operation such as fuel cut. On the other hand, the Wide open and closed throttle position switch, which is built into the throttle position sensor unit, is not used for engine control.

Get Access to Factory Service Manuals.

p0121 chevy cobalt

Related Information. Repair Importance Level: 3. Why is the Engine Light ON?Troubleshooting and testing the throttle position sensor TPS or diagnostic trouble codes: P, P, P on your 2. You won't need a scan tool to follow the steps in this article. All of the three tests in this article are explained in a step-by-step manner and at the end of each test, you'll get a detailed interpretation of the possible results of the test.

This is a very easy and fast test you'll spend about 20 minutes or so doing all three tests but before you start, I recommend you read the entire article first, especially read the section: How The Throttle Position Sensor Works.

OK, let's jump into this first test. By the way, you'll need someone to help you complete this test step. Alright, this is what you'll need to do:. Warm up the engine for about 20 minutes. This throttle position sensor test will be more effective and accurate if the engine is warmed up or at normal operating temperature.

Grab your multimeter and select Volts DC mode. Now, with the red multimeter test lead, and using an appropriate tool like a wire-piercing probeprobe the dark blue DK BLU wire of the throttle position sensor. This will be the wire that connects to the terminal labeled with the letter C in the illustration above. Ground the black multimeter test lead on the battery negative terminal and then have your helper turn the Key On but don't start the engine.

If your multimeter registers something else, don't worry about it just yet, continue with the other steps.

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With the multimeter still connected to the dark blue DK BLU wire and the black multimeter test lead Grounded and the Key in the On position, rotate the throttle plate by hand while you observe the multimeter. The voltage the multimeter registered in test step 4 should increase smoothly as you manually open the throttle plate to its Wide Open Position.

At Wide Open Throttle, your multimeter should be registering about 4. Now, release the throttle plate to its original closed position do this slowly.

Again, keep observing the voltage readings on your multimeter. The voltage should decrease in a smooth and linear fashion back to the exact same voltage you noticed in step 4. OK, now your helper needs to help you with the next steps.

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As your helper taps the throttle position sensor with the screw-driver, you need to open and close the throttle smoothly and slowly of course. What you are trying to confirm with this, is that the tapping of the screw-driver should have not effect on the voltage readings your multimeter is recording. In other words, there should not be any gaps or skips in the readings as your helper taps the TPS.

CASE 1: The multimeter registered a smooth increase or decrease in voltage. This is the correct test result. You can conclude that the throttle position sensor has passed with flying colors. No further tests are needed, since these test results confirm that the TPS is good. This means that the throttle position sensor TPS is bad.

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This is not good, but does not condemn the TPS as bad yet. Two more things need to be verified first, which are making sure the TPS sensor is getting 5 Volts and Ground. Fuel Injector Circuit Wiring Diagram 2. So I stole a bike and asked for forgiveness. This material may not be reproduced without the author's consent. Page 1 Page 2 Page 3. Contents of this tutorial:.P is a somewhat common trouble code with the Chevy Cobalt.

It is relatively serious problem since it leaves your vehicle in failsafe mode. Diagnosing it can be tricky without a good scanner and the knowledge of what you are doing. The symptoms of P are going to vary by year and model, but they certainly are going to cause noticeable changes in the way that your Cobalt drives. This is what you need to address. A good mechanic will utilize a scanner to diagnose when the codes were set and reset them.

If it all checks out and the code comes back, they may go ahead and replace the TPS sensor in question. Most of the time, the problem when P is thrown will be the TPS sensor itself. It no longer is accurately tracking how hard the fuel pedal is being pushed. Diagnosing the issue with a scanner or having a mechanic take a look can save the expense of buying a TPS sensor that your Cobalt does not actually need.

Good luck diagnosing P in your Chevy Cobalt. If there is anything that you would like to add, please leave a comment below. Chevy Cobalt P Symptoms The symptoms of P are going to vary by year and model, but they certainly are going to cause noticeable changes in the way that your Cobalt drives.

Here are the most common symptoms of P The vehicle will hardly respond to the throttle at all. This limited power is a failsafe to keep the vehicle able to move, but not super fast.

The Cobalt may idle differently. Failsafe mode leaves a vehicle in a state that makes it almost impossible to drive and enjoy. Chevy Cobalt P Diagnosis A good mechanic will utilize a scanner to diagnose when the codes were set and reset them.


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