Transmission Control Systems: Testing and Inspection
Diagnosis of Automatic Transmission
Monitoring of the Electronic Transmission 5HP19 / GS8.61.21
Generally:
The electronic controlled automatic transmission is monitored for malfunctions via its control module (TCM). If a malfunction is detected, the TCM is storing the fault information immediately and activates the appropriate contingency-measures.
Implausible Gear or Transmission Clutch Slipping
The EGS identifies the shifted gear under steady state conditions by verifying the signals of two speed sensors inside the transmission. The described monitoring function is only supported in gear range two up to gear range five.
Internal Checks of the TCM
The following is checked in the TCM:
- inadmissible variant
- check of external/internal watchdog
- EEPROM
- RAM and ROM
The monitoring of this components is performed after initialization of the system, that means ignition key in "on" position. A malfunction is detected and the corresponding fault code is stored if one of the above checks is implausible.
Voltage Supply of the Control Solenoid Valves
The solenoid valves are supplied with battery voltage. A threshold of 9 Volt is monitored via the TCM. If the measured voltage exceeds the admissible threshold of 9V a malfunction is detected and the corresponding fault code is stored immediately.
Implausible Shift Lever Position
The shift lever is monitored for the plausibility of its position.
Transmission Speed Sensors
The transmission is equipped with two speed sensors, the first for the input speed called TIS (Transmission Input Speed) and the second for the output speed called TOS (Transmission Output Speed).
A functional check of the transmission speed sensors is made in the following way:
The TIS sensor is monitored above the engine speed 992 rpm against out-of-range low and out-of-range high transmission input speed values and the TOS sensor is monitored above a vehicle speed greater than 85 km/h for equal to zero or reaching the out-of-range high threshold for the transmission output speed.
Torque Converter Lockup Clutch
The Torque Converter Lockup Clutch is monitored against slipping, if the given closing-rate from the TCM has reached a specified threshold. If the difference between the engine speed and transmission input speed exceeds a threshold of 250 rpm slippage, a malfunctioning of the torque converter lockup clutch is detected and the corresponding fault code is stored.
Solenoid Valve of the Torque Converter Lockup Clutch
The solenoid valve of the converter is monitored continuously against the following:
- short circuit of shift valve against ground
- short circuit of shift valve against battery voltage
- broken cable of shift valve
Control Solenoid Valves
The control solenoid valves are monitored continuously against the following:
- short circuit of the valves against battery voltage
- short circuit of valves against ground
- broken cable of valves
Transmission Fluid Temperature Sensor
The transmission fluid temperature sensor is monitored continuously against the following:
- implausible temperature range
- short circuit of the temperature sensor against battery voltage
- short circuit of the temperature sensor against ground
- broken cable of the temperature sensor
Engine Speed
The engine speed is monitored against engine over-speed.
CAN Communication
The CAN bus is used for sending and receiving of signals, which are used for driving functionality within the TCM and other ECUs.
The interface lines of the CAN bus transceiver component are monitored against an electrical failure (CAN Bus-Off), thus detecting, if the whole communication has broken down.
Each message, containing important signals, which are used for driving functionality, is monitored against a message failure within a timeout range.
A further monitoring is done on several signals, which have an influence on driving functionality or are part of another monitoring-strategy. This signals are monitored through fault notifications from the ECUs that sends the required signals.
Transmission Control Module Inputs/Outputs:
Note: Column "Diag" shows the pins which are necessary for diagnostic operation.