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Testing 4L60E and 4L80E Shift Solenoid Electrical Faults,
DTC P0753, P0758, P0973, P0974, P0976 and P0977:

A shift solenoid electrical DTC can be diagnosed with a volt/ohm meter, 12 volt test light and patience. This is assuming you do not have access to a scan tool that will operate the solenoid circuits in special test mode. A shift solenoid electrical DTC can be any of the following: P0753, P0758, P0973, P0974, P0976 and P0977.

The shift solenoids are powered from an ignition source through the "trans" fuse in the fuse block and grounded by the PCM. The 4L60E and 4L80E shift solenoids are on/off type solenoids.If only one DTC is set chances are good you have a grounding issue. If more than one solenoid DTC is set chances are good you have a power supply issue.

To check for a 12 volt power supply disconnect the transmission harness connector at the transmission. Insert a #59 drill bit in the female terminal E (also checks that terminal is not loose, drill bit should drag slightly as it is inserted and removed) of the connector on the PCM side of the harness. Turn the ignition switch to the key on engine off position. Using a 12 volt test light from terminal E (PNK or PNK/BLK) to engine ground the test light should light brightly. If the light does not illuminate or is dim use the volt meter and check voltage. If voltage is low or non existent this is an indication of a faulty ignition switch, blown fuse, a short to ground or open in the wiring.

If everything is good with the power source turn the ignition switch to the off position. Use an old harness connector with a length of wire still attached to all the terminals as a test harness. Plug the test harness to the connector on the transmission. Check resistance of 1-2 solenoid with your meter from terminal A (LT GRN) to terminal E (PNK or PNK/BLK). Resistance value should be 20 to 30 OHMs. Then check resistance of 2-3 shift solenoid with your meter from terminal B (YEL or YEL/BLK) to terminal E (PNK or PNK/BLK). Value should be 20-30 OHMs. A quick test of solenoid operation; with the transmission harness disconnected and the test harness attached apply 12 volts to ternimal E while grounding terminal A or terminal B listen for the clicking of the solenoid. If resistance values are different or solenoid does not "click" when powered replace solenoid.

If all is good, the next step is to check for a ground or an open in the wiring from the PCM to the transmission. Disconnect the harness from the PCM and the transmission. Using the OHM meter from terminal A check for continuity to ground. Repeat for terminal B. These readings should be infinite. Any resistance value would indicate a short to ground in the wiring. Next using jumper leads check the wiring for continuity from the transmission connector (PCM side) terminal A to circuit 1222 and from terminal B to circuit 1223 of the PCM. You will need a PCM connector diagram for your particular vehicle to determine the correct terminal for these circuits. At this point if all is good you have eliminated everything except the PCM.

To test the PCM, back probe circuit 1222, using your volt meter from this terminal to ground check for less than 50 millivolts with the engine running and the vehicle in park. More than 50 millivolts would indicate a defective PCM ground driver. Repeat for circuit 1223.

To check the PCM ground drivers for thier ability to turn off the ground signal is pretty much impossible without a scan tool. After all the above tests are completed and no faults are found. A quick test would be plug everything back up and test drive the vehicle. If you start out in first gear and when changing to 2nd gear DTC P0753 sets. It is a pretty safe bet the PCM is defective. If you make it through 2nd gear and DTC P0758 sets when changing to 3rd gear again a good bet would be a defective PCM.

Testing with a scan tool that can operate the shift solenoids in special test mode is completely different than the above decribed methods. Refer to the factory service manual for this testing procedure. This testing method will work for factory or aftermarket transmission controllers. Aftermarket controllers may or may not store diagnostic trouble codes depending on manufacturer.

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