ASE A6 “ELECTRICAL” VOLTAGE DROP PART 3
Another example concerning voltage drop is an sensor with excessive voltage on the ground side of the circuit which should be .05 volts but your circuit reads 1.5 volts, indicating excessive resistance.
This will increase the voltage reading on the sensor wire and the computer will interpret this as a higher throttle angle.
The same is true if the ground wire is open on the ground side, this resistor will not drop any voltage and the input signal to the PCM will see an increase of voltage.
In this particular case the PCM will see 5 volts, remember a circuit with an open ground wire voltage does not drop and you will see system voltage through the entire circuit.
This will cause all sorts of problems, from hard starting, hesitation and transmission shifting problems on vehicles with electronic control transmissions.
So in summary high voltage drop on the ground side of the circuit,equal excessive resistance and the signal voltage reading will increase this signal voltage reading will go back to the PCM.
The PCM will interpret this reading as a higher then normal throttle angle, and even set a false TPS code or other related false codes.
ASE A6 “ELECTRICAL” VOLTAGE DROP
Even when a circuit has a two or three wire sensor they all can be affected by resistance and voltage drops. A two wire temperature sensor has a five volt reference wire from the PCM and a ground wire back to the PCM. This circuit is part of a series circuit.
A three wire position sensor has its own ground circuit wire, a separate signal wire and needs a reference voltage wire to send a signal to the PCM for correct fuel injection operation.
Remember the signal wire is performing a voltage drop across the resistor and sending that signal to the PCM. The PCM will interpret this signal voltage as the position of the throttle angle.
So any increase resistance on the ground side of the circuit will send an increase voltage reading to PCM “Power Train Control Module” and this will cause driveability problems and have the possibility of turning on the Malfunction Indicator Light, “MIL”.
Remember before changing any sensor always check the voltage readings, this procedure may say you time and money, or even reduce your daily headaches.
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