Transmission Test Box and Tech 1 Diagnosis

Transmission Test Box And Tech 1 Scan Tool:

A transmission test box, J 38791, and transaxle harness J 38791-10, is recommended to diagnose whether the cause of a problem is in the vehicle PCM wiring harness or in the transaxle.

The test box allows the technician to monitor vehicle electrical outputs through illumination of LED's, measure component resistance or perform other electrical checks through pin-out jacks, and control transaxle shifts or TCC operation while road testing the vehicle to conduct functional tests.

The Tech 1 or other scan tool can monitor engine/transaxle sensors and the PCM for proper operation. LED indicators on the test box monitor the presence of voltage at the PCM ignition input, brake switch, TCC apply solenoid, TCC modulate solenoid, and A Shift and B Shift solenoids. Pin-out jacks for these circuits are also provided just below each respective LED to facilitate probing with a digital volt ohmmeter when required. A gear selector switch and a converter clutch operation switch are located near the bottom of the face panel. A vehicle system ground pin-out jack is located at the bottom.

The test box is installed by connecting its harness connectors between the vehicle harness connector and the transaxle connector, routing the harness under the hood through the driver's door window into the passenger compartment, and inserting the ground connector into the cigarette lighter receptacle.

Using The Transmission Test Box

Transmission Test Box Electrical Diagnosis Chart:

Solenoid Operation:

Transaxle Test Box LED Operation:

^ Before installing the Test Box, check the vehicle diagnostic system for PCM related codes. Diagnose and repair these codes before diagnosing the transaxle.

1. Connect the test box.
A. Disconnect the vehicle transaxle wiring harness from the transaxle.
B. Connect the test box connectors into the vehicle harness and transaxle.
C. Route test box harness under the hood, through the driver's window. Use a tie strap if necessary to keep the test box harness away from the exhaust manifold or cooling fan.
D. Insert the power/ground connector into the cigarette lighter receptacle in the passenger compartment. Observe that the battery LED comes ON.
E. Turn the ignition ON.
F. Set up the Tech 1 or other scan tool.

NOTICE: To avoid damage to the transaxle due to overstress, observe the following when using this tool:
^ Do not start vehicle from a stop in 3rd or 4th gear setting.
^ Do not shift to 1st gear setting above 40 km/h (25 mph).
^ Do not brake torque vehicle with tool attached.
^ Do not move converter clutch switch to the ON position when vehicle speed is less than 40 km/h (25 mph).
^ Do not place vehicle shift selector in manual first or manual solenoid.

2. Place the gear selector and converter clutch switches on the test box to the NORMAL positions.
3. Perform functional tests for brake switch and all gears including TCC. Remember, the engine must be up to minimum operating temperature of approximately 60°C (140°F) for TCC operation. Tests can be done in bay and/or road test. Observe the LED indicators of test box.