P0128 - ECT Below Thermostat Regulating Temperature
Before getting "wrapped around the axle" over this code, be aware this one was real common as far back as the mid '90s. If this is the same issue, it will not affect emissions, therefore it will not turn on the Check Engine light. In cold winter climates, this code will be found in every Chrysler product, and can be ignored. It sets when the coolant fails to reach a predetermined temperature within six minutes of starting the engine. If it's real cold outside, the only way the coolant can warm up fast enough is to start the engine, then immediately zip out onto the highway and reach full speed. Any preliminary idling to let the engine warm up will be sufficient to set this code.
P0101 - Mass or Volume Air Flow Circuit Low Input
This code does not refer to the measured weight of the incoming air being too low, as would occur with a dirty sensing element. It refers to the signal voltage going outside of the acceptable range. For most 5.0-volt sensors, that acceptable range is 0.5 to 4.5 volts. A dirty sensor can not cause this code. The only way for the voltage to reach these values is a defect in the circuitry within the sensor, or a break in one of the wires feeding the sensor.
In this case, a low input code is set when the signal voltage falls below 0.5 volts. (That's for explanation purposes. In actual practice, the threshold for triggering a code will vary, and could be a little higher or lower). If there was a break in the 5.0-volt feed wire, or corrosion between the mating terminals in the connector for that wire, all you'd see in the sensor was the ground circuit, and 0.0 volts output signal. If you watch the signal voltage on a scanner and you see it drop to 0.0 volts, the best suspect is a problem in the 5.0-volt feed wire circuit. If you see the signal voltage drop too low, but not all the way to 0.0 volts, circuitry problems within the sensor is the better suspect.
Thursday, April 18th, 2019 AT 1:29 PM