P0179 2018 GMC Sierra Code - Fuel Composition Sensor Circuit High Frequency
Quick Answer
The Fuel Composition Sensor (FCS), or Flex Fuel Sensor (service parts term), measures the ethanol-gasoline ratio of the fuel being used in a flexible fuel vehicle. Common causes include Faulty Fuel Composition Sensor (FCS) or Flex Fuel Sensor, Fuel Composition Sensor harness is open or shorted, Fuel Composition Sensor circuit poor electrical connection. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
- What it means
- P0179 2018 GMC Sierra indicates Fuel Composition Sensor Circuit High Frequency.
- Common causes
- Common causes include Faulty Fuel Composition Sensor (FCS) or Flex Fuel Sensor, Fuel Composition Sensor harness is open or shorted, Fuel Composition Sensor circuit poor electrical connection.
- Severity
- High - diagnose this code as soon as possible.
- Can I drive?
- Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
Code P0179 2018 GMC Sierra Description
Alcohol content information is supplied to the Engine Control Module (ECM) from the Fuel Composition Sensor. The Fuel Composition Sensor has an ignition positive circuit, a signal circuit, and a ground circuit. The Fuel Composition Sensor uses a microprocessor inside the sensor to measure the ethanol percentage and changes the output signal accordingly. The signal circuit carries the ethanol percentage via the frequency signal. The ECM provides an internal pull up to 5V on the signal circuit, and the fuel composition sensor pulls the 5V to ground in pulses. The normal range of operating frequency is between 50 - 150 Hz. The microprocessor inside the sensor is capable of a certain amount of self-diagnosis. An output frequency between 180 Hz and 190 Hz indicates that the fuel is contaminated. The Diagnostic Trouble Code (DTC) will be set when the ECM detects that the fuel composition sensor output frequency is less than 45 Hz for greater than 6s.
What are the Possible Causes of the DTC P0179 2018 GMC Sierra?
- Faulty Fuel Composition Sensor (FCS) or Flex Fuel Sensor
- Fuel Composition Sensor harness is open or shorted
- Fuel Composition Sensor circuit poor electrical connection
- Faulty Engine Control Module (ECM)
How to Fix the DTC P0179 2018 GMC Sierra?
Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.
Code Tech Notes
What is the Cost to Diagnose the Code?
Labor: 1.0
To diagnose the P0179 2018 GMC Sierra code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.
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Frequently Asked Questions about P0179 2018 GMC Sierra Code
What does the OBDII code P0179 mean on a 2018 GMC Sierra?
Code P0179 indicates a problem with the fuel composition sensor circuit, specifically a high-frequency signal being detected by the engine control module (ECM).
What are the common symptoms of code P0179 on a 2018 GMC Sierra?
Typical symptoms include poor engine performance, reduced fuel efficiency, difficulty starting the engine, and potential illumination of the check engine light.
What causes the P0179 code to appear on a GMC Sierra?
Common causes include a malfunctioning fuel composition sensor, damaged or corroded wiring, a faulty ECM, or contamination in the fuel system.
Can driving with code P0179 damage my 2018 GMC Sierra?
While driving with this code may not cause immediate damage, prolonged operation with fuel composition issues can lead to reduced engine efficiency and potential long-term damage.
How do I diagnose code P0179 on my GMC Sierra?
Diagnosis involves inspecting the fuel composition sensor, checking the wiring and connectors for damage, testing the sensor’s signal output, and scanning the ECM for additional codes.
What is the fuel composition sensor’s role in a 2018 GMC Sierra?
The fuel composition sensor monitors the ethanol content in the fuel and sends this data to the ECM to adjust air/fuel ratios accordingly.
Can a dirty or contaminated fuel system trigger code P0179?
Yes, contamination or water in the fuel system can interfere with the fuel composition sensor’s readings, potentially triggering the code.
How do I fix code P0179 on a 2018 GMC Sierra?
Repairs may include replacing the fuel composition sensor, repairing damaged wiring, cleaning the fuel system, or recalibrating the ECM.
How much does it typically cost to repair code P0179 on a GMC Sierra?
Repair costs vary depending on the issue but typically range from $200 to $500, including parts and labor.
Can a faulty ECM cause code P0179 on a GMC Sierra?
Yes, a malfunctioning ECM can incorrectly interpret sensor signals, leading to the P0179 code.
Discuss the causes and fixes for P0179 2018 GMC Sierra OBDII Code
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