All P1514 Trouble Codes – Don’t Delay to Fix Them! 

P1514 code is a diagnostic trouble code that translates as a throttle control unit issue or diesel exhaust fluid DEF problem depending on your truck. You can fix these by troubleshooting your throttle control. When P1514 shows up for other DTCs, clear those first. 

You are cruising down the road in your truck and suddenly your engine goes on limp mode and the check engine light comes ON. So you hook up your OBD scanner and P1514 DTC (diagnostic trouble code) appears. 

There are several reasons for this code to show up and we will discuss all of them. Continue reading to find out how you can solve this error code. 

What P1514 Trouble Code Means

P1514 code means there is a malfunction in the throttle control unit for Trailblazer, Chevy, Silverado, and GMC. For Kenworth, Peterbilt and Paccar this code refers to a DEF (diesel exhaust fluid) fault. 

In general P1514 trouble code is about a car engine receiving more air with respect to the known throttle position.

P1514 is a diagnostic trouble code that comes on your OBD scanner after turning the check engine light ON. Another telltale symptom of this code is the engine running in limp mode. To fix this code, you need approximately 1 hour of labor.

Source: Youtube  

Manufacturer Specific Definition 

P1514 code slightly differs in meaning depending on the manufacturer. Here in this table, you can see what it means for different trucks at a glance. (0)

TrucksDTC P1514 Code Meaning 
Throttle control unit, intake air flow -excessive

Throttle control unit, intake air flow -excessive
Silverado Throttle control unit, intake air flow -excessive
GMCThrottle control unit, intake air flow -excessive
Chevy Throttle control unit, intake air flow -excessive
DEFOI Urea dosing category fault
Peterbilt DEFOI Urea dosing category fault
PaccarEmission control system Diesel Exhaust Fluid (DEF) dosing fault detected

For trailblazer, Silverado, GMC, and Chevy trucks, P1514 means there is an issue with the throttle control actuator and excessive airflow into the engine.  

Kenworth, Peterbilt, and Paccar trucks have this code which translates as a fault in DEF dosing. However, experts say this code shows up due to the persistence of other DTCs. 

Reasons and Fixes for P1514 Trouble Code 

Six possible reasons might lead to this P1514 trouble code as shown in the table below. We will walk you through every fix step by step. 

TrucksReason Fix 
Trailblazer,Silverado,GMC,Chevy Engine Tuning Scale the tune
Trailblazer,Silverado,GMC,Chevy TAC module Issue Clean/ Replace the module 
Trailblazer,Silverado,GMC,Chevy Faulty MAF SensorClean/ Replace MAF sensor 
Trailblazer,Silverado,GMC,Chevy APP sensor Issue Replace APP sensor 
Trailblazer,Silverado,GMC,Chevy Throttle Body Problem Clean/ Replace throttle body 
Kenworth,Peterbilt,PaccarDEF Dosing Issue  Investigate DTCs

P1514 DTC Common Symptoms:

Trailblazer, Silverado, GMC, and Chevy trucks will show these symptoms with P1514 code: 

  • Check Engine light on 
  • Engine running on limp mode 
  • Engine stalling or misfiring 
  • Car won’t start (1)

Kenworth, Paccar, and Peterbilt trucks will show these symptoms:

  • High emission (DEFOI Urea dosing category fault)
  • Increased DEF consumption 
  • Equipment Failure ( DEF pump, Filter) (2) 

Reason 1: Engine Tuning 

Tuning your engine might be the main reason for P1514 DTC code on your OBD scanner. Engine tuning is done with the purpose of making your truck perform better in terms of speed, acceleration, torque, and power. 

When you tune up your truck, you are changing your intake/ exhaust manifold. P1514 code especially comes on after a speed density (SD) tuning. (3)

Solution: Scale the Tune

Scale the tune by (temporarily) bumping up your TPS Sensor, and Calc. airflow table by 15%. You might have to go a little higher depending on your mods. (4) 

Assuming you’re using an HP tuner for tuning up, navigate to Engine Diagnostics > General > TPS > Calculated Airflow vs. TPS vs. RPM Table. 

Multiply this table by 15% and the DTC code should disappear.

To multiply, 

  • Enter the value to multiply by in the space next to the math symbols in the
  • toolbar.
  • Click the multiplication sign.

Now you need to write the tune back to the car. Follow the below procedures to do that:

  • Make sure both the car battery and laptop battery are fully charged. Open VCM Editor and make sure a valid tune file is open. 
  • Select Write vehicle and turn on the car’s ignition but don’t start the engine. 
  • Ensure all components and doors are closed. 
  • Wait for 10 to 15 seconds then click the Write button. 
  • After successful completion is indicated, turn off the ignition and remove the connecting cable. 
  • Wait a minimum of 15 seconds to start the car. 

If you are still getting reduced engine power then you need to scale your IFR table similarly. (5)

Reason 2: TAC Module Issue 

Throttle actuator control (TAC) module controls the throttle position and consequently the amount of air into the engine. If the TAC module is faulty, then it will let excessive air into the cylinder causing P1514 DTC. 

If the TAC harness is open or shorted then P1514 comes on. Similarly, poor electrical connections also lead to that same DTC code. 

Source: LS2

Solution: Clean/ Replace the module 

Here is how you can solve this:

  • Check for loose/ torn wirings and connections of the TAC module. The TAC module is located between the air intake and the intake manifold. Tighten the loose wirings. Make sure no wires are cut. Replace the cut wires. 
  • Remove wirings from the TAC harness and clean the port of the module. 
  • If your TAC module is faulty, replace it with a new module.

The price of the TAC module varies. However, a GM TAC module costs around $145. 

Maintenance Guide 

Regularly check to make sure your TAC is free from water contamination.

Reason 3: MAF Sensor Problem

A dirty or faulty mass airflow MAF sensor won’t be able to calculate the airflow correctly. When the MAF sensor has an issue then the exhaust gas will be black.

Solution: Clean/ Replace the Sensor

Here is how you can solve the MAF issue:

  • Clean the dirty MAF sensor. It’s a delicate procedure and this solution is often temporary. Follow this procedure to clean the MAF sensor. 

Locate the MAF sensor between the air filter and throttle body and remove all the electrical connections. Then remove the sensor and spray 10 to 15 spurts of MAF sensor cleaner. Don’t rub the sensor and wait a few minutes to let it dry before reinstalling it. 

  • Replace the MAF sensor if it’s gone bad. Usually, a MAF sensor has four wires. Use a min-max multimeter to get voltage readings. Connect one wire to the ground and another to return lead, and you should see 4V or 4V+ on your multimeter. Check all four wires like this and if you don’t get a reading >=4V then the MAF sensor is faulty. 

The MAF sensor costs from $89 to $380. Install the air filter accurately while replacing the MAF sensor. 

Maintenance Guide 

Clean the MAF sensor regularly using a MAF sensor cleaner. 

Reason 4: APP sensor Issue 

When any Accelerator pedal positions (APP) sensor, on the accelerator pedal assembly, is faulty this DTC might show up. These sensors control the accelerator of your truck and might fail due to corroded wirings, poor connection with the powertrain control module PCM, and contamination inside the sensor. 

Solution: Replace the APP sensor  

Check for loose connections of the APP with PCM. Tighten the loose connections. Check the voltage reading with a multimeter to see if it’s within the set limit which is usually around 5 volts. 

If the voltage reading is below/above this set limit, the APP sensor is faulty. Hence, you need to replace the sensor.

Here is how to replace APP sensors:

Step 1: Unplug the negative battery terminal

Step 2: Locate the APP sensor on the accelerator pedal and press the knob to unplug it

Step 3: Remove the wiring harness and mounting screw of the APP sensor

Step 4: Take out the old APP sensor 

Step 5: Install the new sensor 

Step 6: Reconnect the electrical wirings

Step 7: Plug in the negative battery terminal 

Maintenance Guide 

Regularly check for mechanical damage of your APP sensor. With a visual inspection, you will be able to identify loose connections and damages.

Reason 5: Throttle Body Problem 

The throttle body contains two throttle position sensors and a motor. These components control the opening of the throttle valve. If there is an issue with the throttle body then, the P1514 code will appear. 

Solution: Clean/ Replace throttle body 

1. Check if the throttle body is dirty. If it is, then thoroughly clean it. Here’s how to clean a throttle body.

  • Disconnect the air duct from the throttle body with a Phillips screwdriver by loosening the hose clamp. 
  • Spray some throttle body cleaner inside the throttle body. Rotate the throttle plate while cleaning. With a small brush, scrub the interior. 
  • Apply compressed air into the throttle body to dry off the spray. 
  • Reattach the air duct and electrical connections you unplugged before. 

2. Check the TPS sensor to see if it’s correctly installed. Use a multimeter to check If it’s faulty. Put the multimeter in the 10 DC voltage range. Connect the black/negative to the ground terminal of the TPS and connect the red/positive to the reference voltage terminal of the sensor. 

Then the multimeter reading should show 5V reading when the throttle is closed and 0.2 to 1.5V when its open. If not then the TPS sensor is bad. 

Replace it with a new one. This issue is common with both the P1514 and P1222 DTC code

3. Check for leaks in the throttle body. Replace the throttle body if it has any leaks. 

Here’s how to replace a throttle body. Throttle body replacement costs around $250 to $650 including the labor cost.  

Maintenance Guide 

Thoroughly clean your throttle body every 75,000 miles. 

Reason 6: DEF Dosing Malfunction

When your vehicle is running low on diesel exhaust fluid (DEF), it’s called DEF dosing malfunction. Diesel exhaust fluid is added to exhaust gas to reduce harmful emissions. 

Solution: Investigate DTCs

Do not troubleshoot this DTC since this comes on due to other persistent trouble codes. 

Here is how you solve this DTC.

Step 1: Investigate related DTCs. To resolve P1514, investigate any of these related active codes:

Р3808; Р3809; Р3810; Р3812; Р3813; Р3814; Р3844; Р3845; P3846; P3847; P3848; Р3856; Р3857; Р3858; Р3859; Р3862; Р3890; Р3904; Р3905; Р3909; Р3912; Р3978; Р3980; Р3985; Р3986; Р3994; P3996

Step 2: Perform a cycle called repair verification if you have DTCs to make sure all DTCs are cleared. To complete a verification drive cycle, first start SRT with the brakes set. After that turn the engine on and let it run in idle mode for a few minutes.

Step 3: If the above-mentioned solution doesn’t work for you, and you need further assistance, please contact the Specific engine support center.

How Serious Is P1514 Code?

The P1514 code is quite serious and we recommend you fix the P1514 code as soon as possible. Depending on what is the reason behind your code, labor charge and time will vary. The same goes for the components’ price. 

Do You Need To Fix P1514 Code Immediately? 

Yes, you need to fix the P1514 code immediately. Trouble codes are there for you to fix the underlying issues. Don’t try to erase the code without fixing it. 

What Happens If You Don’t Fix The P1514 Code? 

If you don’t fix the P1514 code then your engine will continue to run in limp mode. Increased fuel consumption and continuous engine stalling can also happen for this. Moreover, your engine might stop running altogether. 


We hope this article helped you fix the P1514 code and put your engine back to normal. Whether it was a fuel injection issue, the persistence of other DTC, or a DEF dosing issue, we provided all the solutions. 

Leave a Comment

Written By

Photo of author

William Baldwin

This Is William Baldwin, The Founder & Managing Editor of this website. Me and my team share automotive tips, tricks, and news

Fact Checked And Mechanically Reviewed By


Talha Atta

Talha Atta, a Mechanical Engineer and experienced technical content writer and editor at with a passion for the automotive industry.