Here are the current waveforms for the Hyundai Sonata that prove that the circuit is good to the internal power splice for the overdrive and second gear solenoids, and the failure is between that point and the harness pin at the transaxle connector for the overdrive solenoid ground control. (yellow/white) At the same time, these captures also prove that the circuit is going open and not grounding. This first capture is normal operation. The red trace is from a current probe that is attached to the common power input for the solenoids. The green trace is the overdrive solenoid circuit that is randomly failing. The tan is the second gear solenoid command and the blue is the overdrive solenoid.
One of the first things you should notice are the three rises in current on the red trace. There are three solenoids that are actually powered up by that supply, so you see the PCM confirming all three solenoid circuits. Look at the duty cycles displayed on the tan and blue traces. If you were looking at those circuits with a volt meter, it would average that and display about six volts which is what the transmission shop saw. Notice how the PCM stops pulsing the solenoids and pulls them to ground? You can see the corresponding rise in current when that occurs in the red trace. Now notice how the current rise on the green trace lines up with the grounding of the overdrive solenoid on the blue trace?
These are the key elements that we need to pay attention to when a failure occurs.
So here in the next captures are the circuit failure. I've already mentioned that the circuit is going open, or you could look at it as very high resistance. Try and figure out what you see in these and we can discuss them a little later.
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