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chevy 3500 hd dual fuel tanks pcm and fuel gauge not the saying same level
The fuel level indication height on the instrument shows deviation when filling up gasoline, and the pointer of the fuel gauge will go down during normal driving. When parking and idling, the pointer of the fuel level will go up.
Fault analysis: according to the owner's description, first detect the power line leading to the fuel level sensor. The voltage is 12V, which is normal; The reference voltage from the engine control module is 5V, normal; Then remove the oil pump assembly and check it. In addition, connect the power supply voltage to measure the output voltage of its liquid level sensor. It is a continuous variable voltage, which is also normal.
The indication of the fuel gauge is inaccurate. The fuel gauge is normal when the engine is not running, and the indication of the fuel gauge is low when the engine is running.
Trouble shooting:
1) TAC recommends checking the voltage to ground of the two wires of the fuel pump float, checking whether the fuel pump float interferes with the top of the fuel tank, and trying to replace the fuel pump float and combination instrument.
2) The maintenance personnel found that the voltage of the grounding wire of the fuel pump float to the ground was too high when the engine was running.
Troubleshooting:
Troubleshooting after handling ground point x45.
Fault analysis of fuel level:
The fuel level sensor and the fuel pump are grounded together at x45. The voltage drop that may be caused by poor contact of this grounding point will increase when the fuel pump is running (high current), and the impact on the electrical system will also increase.
The signal of high and low fuel level is first transmitted to the instrument through the engine control module; Second, the engine control module judges the fuel level by detecting the potential on the No. 3 wiring; Third, the float sliding resistance on the liquid level position sensor shares 12V power supply with the oil pump motor. Combined with the fault phenomenon described by the owner, the fuel gauge pointer will go down during normal driving, and the fuel level pointer will go down during parking and idling, which can judge the wave generated by the working voltage of the oil pump under different working conditions the fluctuation of float signal voltage will be caused by dynamic, which may cause instability of float voltage and lead to deviation of feedback signal.
Without affecting the normal operation of other components, combined with their own experience, they decide to make certain changes to their lines to achieve the purpose of troubleshooting.According to the working principle of fuel level, the fuel level will not change until the ignition key is turned on. As long as the problem of float 12V power supply is handled, the fault can be eliminated.
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