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#1
11-29-2005, 10:44 AM
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2002 Sub P0178 code
My '02 is giving this code on the fuel sensor. Low input voltage on the fuel compensation. What's the next step? Get a dealer to check the fuel module?
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#2
11-29-2005, 08:38 PM
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Re: 2002 Sub P0178 code
According to my 03 service manual the code you are referencing is generated by the PCM per the fuel composition sensor. It sends the PCM info on ethanol content and fuel temp. The diagnostics for this code go on to check the output from this sensor, whether the circuit is good, bad connections, bad PCM, etc. The dealer tech will know exactly what to check.
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#3
11-29-2005, 08:54 PM
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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.
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