ON Car: Elecntronic trasmissions / Scan Tools

ElectronicTransmissions and Scan Tools

Vehicle Holden Year 2002 Engine

PCM: Powertrain Control Module

TCC: Torque Converter Clutch

TPS: Throttle Position Sensor

ECT: Engine Coolant Temperature

VSS: Vehicle Speed Sensor

PSA: Pressure Switch Assembly (Transmission Range Fluid)

TTS: Transmission Temperature Sensor

Block Diagram

Circuit Diagram of Power-train Control module System



Shift Solenoids Malfunction

When the vehicle is shifted into drive and starts on the first gear, shift solenoid all the solenoid are in-cage which mean its ON. If the transmission automatically shifts from first to second gear, this turn 1-2 OFF and switches 2-3 solenoid ON. Now when the transmission automatically shifts to third gear, both would not in-cate. and so the solenoid should be in OFF position this called fail safe. And last when automatic shifts into fourth gear, shift solenoid 1-2 is ON and 2-3 is OFF.

Safety Mode

In some case particularly when third gear automatically shift and where solenoid switch off, and the vehicle would still driving. Safety mode switches take place encase of something could go wrong. With the engine of six cylinder, the safety mode would turn both solenoid off at third gear and the vehicle would travel at about 40-30 km/h, but with the powerful engine, this would have the torque to climb up hill.

Codes: 

 DTC67: Torque converter clutch or QDM to circuit fault. There’s a fault in the circuit sensor

 DTC27: Transmission fluid pressure switch assembly open circuit

1st Problem Testing: Disconnect jumper harness from transmission than connect the end to the power-train harness turn on the ignition while using a multi-meter to check the voltage. This test shows to check power to the torque converter clutch solenoid.

2nd Problem Testing: Check for fluid lever and use the scan tool to identify the fault

On-Car Transmission Exercises

 Vehicle: Toyota Motor: 7A-FE 1.8L Year 1998

  Shift chart:

Solenoids (gear)	O/D Turn OFF	O/D Turn ON
First gear Solenoids	OFF (Lock up solenoid)	OFF
Second gear solenoids	OFF	OFF
Third gear Solenoids	ON (Lock up solenoid) at 2850RPM	OFF
Fourth gear solenoids	OFF	ON at 1600rpm, solenoid SLU and Lock up solenoid)

O/D TURN OFF

With Overdrive switches OFF

The video show the transmission test with the O/D is switch off and the transmission can not shift to 4th gear because of torque and ratio (0.8 of 1). when the 3rd gear approach at about 2500rpm engine speed, the torque converter clutch lock up turns ON the solenoid and lock the turbine and flywheel. This is when the transmission catch up with engine speed. 

O/D TURNS ON

 The 4th gear is now activated and the clutch lock up solenoid switches at engine speed of 1600rpm.

Shift Chart