p0178 error code

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Tahoe1973

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Good evening everyone,
I am sure i am gonna sound like a broken record but I have a 2002 tahoe that is throwing a p0178 error code (fuel consumption sensor low voltage). i have already replaced the sensor itself and the pcm/ecu. i checked the voltage on the three wire connector and am getting 5 volts to the white wire(this wire runs to pin 56 at the pcu/ecm which i believe is the signal wire)..14.4 to the pink wire(i believe this is the ignition wire) and 0 to the black (ground). i checked these with the vehicle running. any ideas as to why i would still be getting the code ? And do any of you know who would sell a bypass for this flex fuel sensor ?
 

OR VietVet

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Welcome to the forum, sorry the info I found is all ran together.

P0178 Fuel Composition Sensor Circuit Low Input OBD-II Trouble Code Technical Description Article by John Ingalls Former Service Manager & Air Force Mechanic Fuel Composition Sensor Circuit Low Input What does that mean? This generic powertrain diagnostic trouble code (DTC) typically applies to all OBD-II equipped vehicles including but not limited to Ford, BMW, Chevy, Pontiac, Mazda, VW, Honda, Scion, Land Rover, etc.

There are four trouble codes commonly associated with fuel composition sensor circuit malfunctions. This circuit is also referred to as the as the flex fuel sensor circuit and the OBDII codes that are triggered by the Engine Control Module (ECM) when this circuit malfunctions are P0176, P0177 and P0179. The fuel composition sensor circuit monitors the amount of ethanol in the gasoline on a flex fuel engine. The amount of ethanol can very every time you fill up the tank requiring appropriate adjustments for optimal performance and fuel economy.

The fuel composition sensor circuit sends a signal to the ECM based on the ethanol level. The ECM adjusts the ignition timing and fuel injector pulse width accordingly to burn the fuel more efficiently. The end result is improved performance, reduced pollution and increased fuel economy.

Code P0178 is set when the ECM detects a low voltage situation within the fuel composition sensor circuit. In most circumstances the presence of a P0178 or P0179 is a very good indication that the problem is electrical in nature.

Code Severity & Symptoms The severity of this code is moderate. Symptoms of a P0178 engine code may include: Increased fuel consumption Poor performance Check Engine Light illuminated Engine stalls

Causes Typically, potential causes for this code include: Faulty Fuel Cap Contaminated fuel Faulty Fuel Composition Sensor Corroded or damaged connector Damaged or restricted fuel line Faulty or damaged wiring Faulty ECM

What are the most common repairs? Replacing the Fuel Cap Replacing contaminated fuel Cleaning corrosion from connectors Repairing or replacing wiring Replacing Fuel Lines or fittings Replacing the Fuel Composition Sensor Flashing or replacing ECM

Diagnostic and Repair Procedures Note: The first step in the troubleshooting process for any malfunction is to research the Technical Service Bulletins for the specific vehicle by year, model and power plant. In some circumstances this can save a lot of time in the long run by pointing you in the right direction.

Basic Steps Examine the condition of the fuel cap Examine the condition of the fuel for contamination Visually inspect the circuit connections and wiring Visually inspect the condition of the fuel lines for obvious defects Check electrical connections for security and corrosion

Advanced Steps Note: The advanced steps become very vehicle specific and require the appropriate advanced equipment to perform accurately. These procedures require a digital multi meter and the specific technical references for the vehicle. Voltage requirements will very based of the specific year, model and engine in the vehicle.

Circuit Checks With the key in the off position and with the sensor and ECM connected check for power and ground referencing the appropriate technical data. Ground should always read 0 volts and power should be 5 volts or 12 volts based on the vehicle and the system configuration. The specific technical manual or online reference material for your vehicle will guide you through this process. If all of these readings are correct the associated component most likely requires replacement. Frequency checks are recommended in some troubleshooting procedures to specifically pinpoint the source of the malfunction. If this process identifies the absence of a power source or ground, continuity testing may be required to check the integrity of the wiring. Continuity tests should always by performed with the power removed from the circuit and the normal readings should be 0 ohms of resistance unless otherwise specified by the technical data. Resistance or no continuity is an indication of faulty wiring that must be repaired or replaced.


 
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Tahoe1973

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Welcome to the forum, sorry the info I found is all ran together.

P0178 Fuel Composition Sensor Circuit Low Input OBD-II Trouble Code Technical Description Article by John Ingalls Former Service Manager & Air Force Mechanic Fuel Composition Sensor Circuit Low Input What does that mean? This generic powertrain diagnostic trouble code (DTC) typically applies to all OBD-II equipped vehicles including but not limited to Ford, BMW, Chevy, Pontiac, Mazda, VW, Honda, Scion, Land Rover, etc.

There are four trouble codes commonly associated with fuel composition sensor circuit malfunctions. This circuit is also referred to as the as the flex fuel sensor circuit and the OBDII codes that are triggered by the Engine Control Module (ECM) when this circuit malfunctions are P0176, P0177 and P0179. The fuel composition sensor circuit monitors the amount of ethanol in the gasoline on a flex fuel engine. The amount of ethanol can very every time you fill up the tank requiring appropriate adjustments for optimal performance and fuel economy.

The fuel composition sensor circuit sends a signal to the ECM based on the ethanol level. The ECM adjusts the ignition timing and fuel injector pulse width accordingly to burn the fuel more efficiently. The end result is improved performance, reduced pollution and increased fuel economy.

Code P0178 is set when the ECM detects a low voltage situation within the fuel composition sensor circuit. In most circumstances the presence of a P0178 or P0179 is a very good indication that the problem is electrical in nature.

Code Severity & Symptoms The severity of this code is moderate. Symptoms of a P0178 engine code may include: Increased fuel consumption Poor performance Check Engine Light illuminated Engine stalls

Causes Typically, potential causes for this code include: Faulty Fuel Cap Contaminated fuel Faulty Fuel Composition Sensor Corroded or damaged connector Damaged or restricted fuel line Faulty or damaged wiring Faulty ECM

What are the most common repairs? Replacing the Fuel Cap Replacing contaminated fuel Cleaning corrosion from connectors Repairing or replacing wiring Replacing Fuel Lines or fittings Replacing the Fuel Composition Sensor Flashing or replacing ECM

Diagnostic and Repair Procedures Note: The first step in the troubleshooting process for any malfunction is to research the Technical Service Bulletins for the specific vehicle by year, model and power plant. In some circumstances this can save a lot of time in the long run by pointing you in the right direction.

Basic Steps Examine the condition of the fuel cap Examine the condition of the fuel for contamination Visually inspect the circuit connections and wiring Visually inspect the condition of the fuel lines for obvious defects Check electrical connections for security and corrosion

Advanced Steps Note: The advanced steps become very vehicle specific and require the appropriate advanced equipment to perform accurately. These procedures require a digital multi meter and the specific technical references for the vehicle. Voltage requirements will very based of the specific year, model and engine in the vehicle.

Circuit Checks With the key in the off position and with the sensor and ECM connected check for power and ground referencing the appropriate technical data. Ground should always read 0 volts and power should be 5 volts or 12 volts based on the vehicle and the system configuration. The specific technical manual or online reference material for your vehicle will guide you through this process. If all of these readings are correct the associated component most likely requires replacement. Frequency checks are recommended in some troubleshooting procedures to specifically pinpoint the source of the malfunction. If this process identifies the absence of a power source or ground, continuity testing may be required to check the integrity of the wiring. Continuity tests should always by performed with the power removed from the circuit and the normal readings should be 0 ohms of resistance unless otherwise specified by the technical data. Resistance or no continuity is an indication of faulty wiring that must be repaired or replaced.


Thankyou Sir !
 
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