Bench Testing the 6L50-6L80-6L90-6T70-6T75 TEHCM GM limits bench diagnosis of the
solenoids to using the test plate. But you can test solenoid electrical opera- tion with a DVOM, just as you would any other solenoid. Lay the TEHCM on the bench and
inspect the solenoid terminals on the side of the TEHCM for any debris that may be bridging the terminal welds. If you discover any debris, clean it off; it may be causing the problem. If no debris is present, set your
meter to measure Ohms and connect the leads across the solenoid you wish to test. The solenoid resistance should read:
Shift Solenoid (On/Off solenoid)
20-40 ohms (figure 3A). Shift and Line Pressure Solenoid
(PWM solenoid) 3-8 ohms (figure 3B). You can also check current flow
through the solenoids. The manufac- turer doesn’t recommend this test for PWM solenoids, but it can be done in a safe manner if you limit how long you leave the current flowing through the solenoid. • Connect one solenoid terminal to a fused voltage supply.
• Using your meter, connect the other solenoid terminal to the voltage supply ground; don’t leave the solenoid energized too long.
• Read the amperage on your meter. Normal amperage based at normal solenoid resistances and a measured 12-volt supply should be: Shift Solenoid (On/Off sole- noid) 0.3–0.7 amps at 12 volts (figure 4A). Shift Solenoid (PWM sole- noid) 1.5–4.0 amps at 12 volts (figure 4B).
If the resistance or the amperage
values are incorrect the solenoid has failed and you’ll need to replace the TEHCM.
Solenoid Cleaning Process If you have a solenoid perfor-
mance DTC or the solenoid fails the air bench test, you should try the sole- noid automated cleaning process before replacing the TEHCM. This process takes place when the TEHCM is in the transmission and the transmission is in
18 Figure 3B: PWM solenoid resistance: 3-8 ohms the car. Solenoid cleaning is an automated
process initiated by your scan tool. If your scan tool is equipped, the process
will raise engine RPM and raise and lower line pressure while the sole- noids are being commanded on and off by the TCM. This process is fully
GEARS August 2012
Figure 3A: On/off Solenoid resistance: 20-40 ohms
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