Electrical/Garage Shift Test
Electrical/Garage Shift ProcedurePerform this test before a hoist or road test in order to make sure that electronic control inputs are connected and operating. If you do not check the inputs before operating the transmission, you could misdiagnose a simple electrical condition as a major transmission condition.
A scan tool provides valuable information. Use a scan tool for accurate diagnosis.
1. Move the gear selector to Park (P) and set the parking brake.
2. Connect the scan tool to the DLC terminal.
3. Start the engine.
4. Connect power to the scan tool.
5. Verify that the following signals are present on the scan tool:
^ ENGINE SPEED
^ TRANS Input Speed Sensor (ISS)
^ TRANS Output Speed Sensor (OSS)
^ VEHICLE SPEED
^ TFP Switch A/B/C
^ PC ACT. Current
^ PC REF. Current
^ PC DUTY CYCLE
^ BRAKE SWITCH
^ ECT
^ TRANS FLUID TEMP
^ TP ANGLE
^ IGNITION VOLTAGE
6. Monitor the BRAKE SWITCH signal while tapping the brake pedal with your foot:
^ BRAKE SWITCH should be Applied when the pedal is depressed.
^ BRAKE SWITCH should be Released when the pedal is released.
7. Monitor the PRNDL SELECT signal and move the gear selector through all of the ranges:
^ Verify that the PRNDL SELECT value matches the rear range indicated on the instrument panel or the console.
^ Gear selections should be immediate and not harsh.
8. Move the gear selector to Neutral and monitor the Throttle Position (TP) ANGLE signal while increasing and decreasing the engine RPM with the accelerator pedal. TP ANGLE should increase with the engine RPM.
Road Test Procedure
^ Perform the road test using a Scan Tool.
^ Perform this test only when traffic and road conditions permit.
^ Observe all traffic safety regulations.
The PCM calculates upshift points based primarily on two inputs: TP ANGLE and VEHICLE SPEED. When the PCM says that a shift should occur, an electrical signal is sent to the shift solenoids. The solenoids in turn move the valves in order to perform the upshift. The shift speed chart refers to TP ANGLE instead of Min Throttle or WOT in order to make shift speed measurement more uniform and accurate. A scan tool should be used in order to monitor TP ANGLE. Some scan tools have been programmed to record shift point information. Check the instruction manual in order to see if this test is available.