A/T - KM175 Torque Converter Clutch Diagnosis
DATE: 1996TECHNICAL BULLETIN # 330
TRANSMISSION: KM175 Series
SUBJECT: Damper clutch diagnosis
APPLICATION: Mitsubishi, Chrysler, Hyundai, Eagle
KM1 75 Series
(includes KM 176, 177, F4A21, 22, 23, 33 and W4A32 and 33)
Damper Clutch Diagnosis
KM175 series transaxles have a damper clutch (also called the torque converter clutch). Most problems with this system can be broken down into three categories.
^ Damper clutch always applied (go to step 1).
^ Damper clutch never applies (go to step 3).
^ Damper clutch slips (go to step 5).
[Step 1]
Damper clutch always applied. Unplug the solenoid connector. If the engine stalls, in gear, go to step two. If not check the voltage of pin two at the solenoid connector (figure 1).
NOTE:
Voltage should be checked with the solenoid harness connected.
Voltage should be zero volts when the damper clutch is off (the voltage will increase to a maximum of three volts, to engage the damper clutch. Some 1993 and later models will go as high as 12 volts. If voltage is present go to step two. If voltage is not present a diagnostic of the TCU is required.
[Step 2]
Remove the lower portion of the valve body, and block the damper clutch control valve in the direction the spring pushes it (figure 2). Reinstall the lower portion of the valve body. If the engine stalls when the transaxle is in gear replace the pump or the torque converter. If the engine does not stall, then replacement of the damper clutch control solenoid valve (DCCSV) or the valve body may be required.
NOTE:
A clogged cooler can also cause this condition.
[Step 3]
Damper clutch never applies.
Check for voltage at the DCCSV terminal on the solenoid connector (figure 1). This should be done while driving the vehicle. If voltage is present go to step four. If voltage is not present perform a diagnostic of the TCU. On models without an ATF temperature sensor, an engine coolant sensor determines operating temperature. There is no code for the engine coolant temperature sensor; nor can it be checked by monitoring serial data with a scan tool. To check the sensor, simply unplug the sensor connector and check for voltage at terminal B (figure 3). It should be approximately 12 volts. If not check the connection between the TCU and engine coolant sensor terminal B. If voltage is correct ground terminal B of the connector and road test the vehicle. If the damper clutch engages, replace the engine coolant sensor.
[Step 4]
Connect a pressure gauge to the torque converter pressure tap (figure 4). Normal pressure is approximately 50-70 psi with the lock-up off (29-34 psi for 1985-86 models). When lock-up is commanded on, pressure will drop to 0-10 psi. If this occurs, the problem is in the torque converter. If pressure does not drop when commanded, either the damper clutch control valve is stuck or the damper clutch control solenoid valve has failed.
[Step 5]
Damper clutch slips.
Check torque converter pressure as in step four. If torque converter pressure is normal (0-10 psi), when commanded on, the problem is in the torque converter. If torque converter pressure is higher than normal when commanded on, the problem is usually caused by a clogged damper clutch control solenoid valve, a torque converter control valve that is stuck open or low reducing pressure. Reducing pressure should be approximately 50-75 psi (36-56 psi for 1995-96 models).
NOTE 1:
Reducing pressure can be adjusted by turning the reducing pressure adjusting screw (figure 2, item 10).
NOTE 2:
All models from 1985-1991 have a calculated amount of slip to the clutch. The MINIMUM amount of allowable slip is approximately 50 rpm. This is done in an effort to minimize torsional vibration from the engine. Most 1991 and later models (except Hyundai) allow a 100% lock-up. These models have a damper assembly built into the torque converter to reduce torsional vibrations.