Question about 2002 GMC Yukon XL

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2002 GMC Yukon XL gives me a P0178 code meaning Fuel Composition Sensor out of frequency out of range. I am reading 5 VDC on the female connector to the sensor. What should it be? Ans where is it getting its signal from?

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Posted on May 29, 2011

  • Jonah Oneal May 30, 2011

    IF SYSTEM VOLTAGE OVER 10.9 VOLTS AND THE PCM DETECTED THE FUEL COMPOSITION SENSOR SIGNAL FREQUENCY WAS LESS THAN 45 HZ FOR 12.5 SECONDS. THE FUEL COMPOSITION SENSOR SIGNAL FREQUENCY AT 32 DEGREES FAHRENHEIT. OR HIGHER IS 138 HZ AT 88 % ETHANOL. POSSIBLE CAUSES FCS SIGNAL CIRCUIT IS OPEN OR SHORTED TO GROUND, FCS POWER CIRCUIT IS OPEN CHECK POWER FROM THE ECM FUSE, FCS GROUND CIRCUIT IS OPEN BETWEEN THE SENSOR AND THE PCM, FCS IS DAMAGED OR HAS FAILED, PCM IS DAMAGED. FCS IS FUEL COMPOSITION SENSOR.

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Could a po178 code cause a repeated fuel pump failure on a 2003 chevy tahoe?


From reading the circuit description from the factory service info . I would say no .
Alcohol content and fuel temperature information is supplied to the powertrain control module (PCM) from the fuel composition sensor (FCS). The FCS has an ignition 1 circuit, a signal circuit, and a ground circuit. The FCS uses a microprocessor inside the sensor to measure the ethanol percentage and fuel temperature, and changes output signals accordingly. The signal circuit carries both the ethanol percentage, and the fuel temperature within the same signal. The signal is both variable frequency and variable pulse width. The frequency signal indicates the ethanol percentage, and the pulse width indicates fuel temperature. The PCM provides an internal pull up to 5 volts on the signal circuit, and the FCS pulls the 5 volts to ground in pulses. The normal range of operating frequency is between 50-150 Hz. The normal pulse width ranges between 1-5 milliseconds. If the PCM detects a signal less than 45 Hz DTC P0178 will set.

How often have you have to replace the pump and how many times ? Just off the top of my head , without test the fuel pump pressure and doing some testing on the electrical circuit , i'd say you have a resistance problem . Something making the pump work harded then it should . Plus how full do you keep your fuel tank ? If you let it get below a 1/4 of a tank regularly ,this could cause premature failure. Also it would be a good idea to do amp draw testing ! Fuel Pump Current Draw

Feb 02, 2017 | Cars & Trucks

1 Answer

Po178 po179


codes p0178 and 179 refer to fuel composition sensor--low and high input respectfully==causes for 178 are wiring--- short to ground--fuel composition sensor--ECM and for 179 are wiring short to positive-- fuel composition sensor---ECM

Dec 06, 2013 | Cars & Trucks

1 Answer

I have a 2002 GMC Yukon xl, every time you give gas it dies, and then wont start for a lil while, what can this be


Could be low on fuel pressure, or a problem with the throttle position sensor. But if the sensor was faulty you should have a trouble code in the computer and the check engine light should be on.

Dec 17, 2012 | 2003 GMC Yukon

2 Answers

P0178


This is a failure code for a fuel composition sensor and man are they proud of these sensors. Last time I put one on the price for the sensor was almost 500.00. This does usually not cause a driveability problem. Here is a circuit description

Alcohol content and fuel temperature information is supplied to the powertrain control module (PCM) from the fuel composition sensor (FCS). The FCS has an ignition 1 circuit, a signal circuit, and a ground circuit. The FCS uses a microprocessor inside the sensor to measure the ethanol percentage and fuel temperature, and changes output signals accordingly. The signal circuit carries both the ethanol percentage, and the fuel temperature within the same signal. The signal is both variable frequency and variable pulse width. The frequency signal indicates the ethanol percentage, and the pulse width indicates fuel temperature. The PCM provides an internal pull up to 5 volts on the signal circuit, and the FCS pulls the 5 volts to ground in pulses. The normal range of operating frequency is between 50-150 Hz. The normal pulse width ranges between 1-5 milliseconds. If the PCM detects a signal less than 45 Hz DTC P0178 will set.

Your stall when put in gear is most likely due to a dirty throttle body (carbon build up). Remove the air intake tube to the throttle body & use a spray can of carb spray & a shop towel to clean the carbon from the throttle bore & plate.

Fuel Composition Sensor Replacement - Removal Procedure
Turn OFF the ignition.
Relieve the fuel pressure

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Raise the vehicle.
Remove the fuel composition sensor fuel composition sensor (FCS) attachment nuts (1).

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Disconnect the FCS inlet and outlet pipes from the FCS.

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Disconnect the FCS electrical connector (1).
Remove the FCS and bracket assembly from the frame rail.

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Remove the FCS bolts and remove from the bracket.


Installation Procedure

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Install the FCS to the bracket and install bolts.
Tighten
Tighten bolts to 10 N·m (89 lb in).

Install FCS and bracket assembly to frame.

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Install FCS bracket to frame nuts.
Tighten
Tighten nuts (1) to 17 N·m (13 lb ft).

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Connect the FCS inlet and outlet pipes to the FCS.

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Connect the FCS electrical connector (1).
Lower the vehicle.
Start the engine and check for fuel leaks.


Hope this helps.

Sep 02, 2011 | 2002 GMC Yukon XL

1 Answer

Hur byter jag växellädsolja på


160....O2 Sensor Circuit No Activity Detected (Bank 2 Sensor 2)

P0161....O2 Sensor Heater Circuit (Bank 2 Sensor 2)

P0162....O2 Sensor Circuit Malfunction (Bank 2 Sensor 3)

P0163....O2 Sensor Circuit Low Voltage (Bank 2 Sensor 3)

P0164....O2 Sensor Circuit High Voltage (Bank 2 Sensor 3)

P0165....O2 Sensor Circuit Slow Response (Bank 2 Sensor 3)

P0166....O2 Sensor Circuit No Activity Detected (Bank 2 Sensor 3)

P0167....O2 Sensor Heater Circuit (Bank 2 Sensor 3)

P0168....Fuel Temperature Too High

P0169....Incorrect Fuel Composition

P0170....Fuel Trim (Bank 1)

P0171....System too Lean (Bank 1)

P0172....System too Rich (Bank 1)

P0173....Fuel Trim Malfunction (Bank 2)

P0174....System too Lean (Bank 2)

P0175....System too Rich (Bank 2)

P0176....Fuel Composition Sensor Circuit

P0177....Fuel Composition Sensor Circuit Range/Performance

P0178....Fuel Composition Sensor Circuit Low Input

P0179....Fuel Composition Sensor Circuit High Input

P0180....Fuel Temperature Sensor A Circuit

P0181....Fuel Temperature Sensor A Circuit Range/Performance

P0182....Fuel Temperature Sensor A Circuit Low Input

P0183....Fuel Temperature Sensor A Circuit High Input

P0184....Fuel Temperature Sensor A Circuit Intermittent

P0185....Fuel Temperature Sensor B Circuit

P0186....Fuel Temperature Sensor B Circuit Range/Performance

P0187....Fuel Temperature Sensor B Circuit Low Input

P0188....Fuel Temperature Sensor B Circuit High Input

P0189....Fuel Temperature Sensor B Circuit Intermittent

P0190....Fuel Rail Pressure Sensor Circuit

P0191....Fuel Rail Pressure Sensor Circuit Range/Performance

P0192....Fuel Rail Pressure Sensor Circuit Low In put

P0193....Fuel Rail Pressure Sensor Circuit High Input

P0194....Fuel Rail Pressure Sensor Circuit Intermittent

P0195....Engine Oil Temperature Sensor

P0196....Engine Oil Temperature Sensor Range/Performance

Nov 20, 2010 | 2004 Volvo S80

1 Answer

P0178 code what the most likely thing wrong


Sorry, I dont know much about this but i can tell you what the code means:
P0178 Fuel Composition Sensor Circuit Low Input

Apr 11, 2010 | 2002 Chevrolet S-10

2 Answers

2002 GMC YUKON XL 1500 MOTOR DIES AFTER GOING


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Jan 23, 2010 | 2002 GMC Yukon XL

1 Answer

Ok I got a 2002 Yukon I did a full tune up


have you erased the hard codes, if any after this initial problem? also might just check your 02 sensor in exhaust in case its reading wrong

Oct 22, 2009 | 2002 GMC Yukon XL

3 Answers

2002 gmc yukon, rich fuel code, low fuel pressure @40


you may have two oxugen sensors on your yukon. if so the oxygen sensor that controls that bank may be bad. from what you mentioned in your complaint, it sounds like it is the oxygen sensor.

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