M/T - Diagnosing The KM162/163 Transmission
TRANSMISSION: KM 162/163BULLETIN # 9002005
SUBJECT: Diagnosis
DATE: Feb 1990
DIAGNOSING THE KM 162/163
MANUAL TRANSMISSION
The KM162 & KM163 are 5 speed manual transaxles used in Mitsubishi and Chrysler import's. (Figure 1).
Since 5th gear is computer controlled, diagnosing 5th gear problems can be difficult unless you have a procedure.
IT'S REALLY A FOUR SPEED
The KM 162 & KM 163 are really 4 speed transaxies with a 2 speed input gear.
The 4 speed section is controlled by the driver, through the shift lever just like all other manual transaxles.
When the shift lever is moved to fifth gear, the computer (select control unit) operates a vacuum actuator which shifts the 2 speed input gear to High range. The transaxle is now overdriving fourth gear.
THE PROBLEMS
Some of the problems you may see on this transaxle are: No fifth gear, no movement in any direction, downshifts from fifth to fourth on its own, hunts or shuttles between fifth and fourth, and poor acceleration from a stop. All of these problems can be related to a malfunction of any of the following components (Figure 2).
^ The Select Control Unit (SCU)
^ The Select Solenoid
^ The Select Switch
^ The Back-up light Switch
^ The Select (vacuum) Actuator
THE SELECT ACTUATOR
The select actuator (Figure 3) is a vacuum diaphragm mounted on the transaxle. Its purpose is to shift the input gear into either low range or high range. In reverse, and first through fourth gears vacuum is directed to the hose closest to the transaxle (front hose) which will have the input gear, in low range. In fifth gear vacuum is directed to the hose furthest away from the transaxle (rear hose) which will shift the input gear to high range.
THE SELECT SOLENOID
The select solenoid is used to direct the vacuum source to either the front or rear hose of the select actuator. When the solenoid is energized by the select control unit, vacuum is directed to the rear hose for fifth gear. When the solenoid is de-energized, vacuum is directed to the front hose.
THE SELECT SWITCH
Closing the select switch signals the select control unit (SCU) that the shift lever has been moved to the fifth or reverse position. The select switch is located on the front of the transaxle and has an alignment mark on it for adjustment purposes (Figure 4 & 5).
THE BACK-UP LIGHT SWITCH
Closing the back-up light switch signals the SCU that the shifter is in reverse. If the back-up light switch is closed in all ranges the actuator ball above the switch may be missing.
THE SELECT CONTROL UNIT
The select control unit, or SCU, monitors the status of the select switch and the back-up light switch. In some vehicles, it also monitors the vehicle speed sensor (VSS). When the select switch is closed and the back-up light switch is open and the vehicle speed is above a predetermined value (some cars), the SCU energizes the select solenoid. The best way to check an SCU is to check all the input signals to it. In most cars, the SCU is located behind the drivers side kick panel. When diagnosing the SCU, first check the # 10 fuse in the fuse box. If the fuse is OK, then disconnect the wire harness and use the chart (Figure 6) to check the external controls.
BULLETIN RECAP
KM 162/163
DIAGNOSING THE MANUAL TRANSAXLE
^ Check the vacuum at the actuator. The rear hose should have vacuum in fifth. All other times vacuum should be at front hose.
^ Energize the solenoid vacuum should switch from the front to the rear hose.
^ Check the SCU by using the chart in figure 6
FOR ADDITIONAL INFORMATION:
Transmission Digest February 1990 "Technically Speaking"