Input
Electronic Component Description (Input)Stop Lamp Switch
The stop lamp switch operates vehicle stop lamps and signals several electronic modules on vehicle, including the Transaxle Control Module (TCM)or Powertrain Control Module (PCM). The switch is normally open when the brake pedal is in released position. When the brake pedal is depressed, pressure on the switch plunger is released and the switch closes. If Torque Converter Clutch (TCC) is engaged when brake pedal is depressed, the PCM/TCM will disengage TCC.
Transaxle Fluid Temperature (TFT) Sensor
The Transaxle Fluid Temperature (TFT) sensor is a negative temperature coefficient thermistor that provides information to the PCM/TCM regarding transaxle fluid temperature. The temperature sensor is integrated in transaxle fluid pressure switch assembly which is bolted to the control valve body. The sensor monitors main line pressure from the inside of the control valve body in order to determine the operating temperature of the transaxle fluid. The sensor uses an O-ring seal to maintain fluid pressure in the control valve body.
The internal electrical resistance of the sensor varies in relation to the operating temperature of the transaxle fluid. The PCM/TCM sends a 5-volt reference signal to the temperature sensor, then measures voltage drop in the electrical circuit. A lower fluid temperature creates a higher resistance in the temperature sensor, thereby measuring a higher voltage signal.
The PCM/TCM measures this voltage as another input to help control line pressure, shift schedules and TCC apply. When the TFT reaches 140°C (284°F), the PCM/TCM enters hot mode. Above this temperature the PCM/TCM modifies the transaxle shift schedules and TCC apply in an attempt to reduce fluid temperature by reducing the amount of heat generated by the transaxle. During hot mode the PCM/TCM applies TCC at all times in Third and Fourth gears. Also, the PCM/TCM performs the 2-3 and 3-4 shifts earlier in order to help reduce heat generated in transaxle fluid.
TFT Sensor - Temperature to Resistance
TFT Sensor - Temperature-To-Resistance
Output Speed Sensor (OSS)
The Output Speed Sensor (OSS) is a magnetic inductive pickup that relays information relative to vehicle speed to the PCM/TCM. Vehicle speed information is used by the PCM/TCM to control shift timing, line pressure, and TCC apply and release.
The OSS mounts in transaxle case near the speed sensor rotor which is pressed onto final drive assembly. An air gap of 0.27 - 1.57 mm (0.011 - 0.062 inch) is maintained between sensor and teeth on the output shaft speed sensor rotor. The sensor consists of a permanent magnet surrounded by a coil of wire. As the differential rotates, an AC signal is induced in the OSS. Higher vehicle speeds induce a higher frequency and voltage measurement at sensor.
Sensor resistance should be 1500 ohms when measured at 20°C (68°F). Output voltage will vary with speed from a minimum of 0.5 volts AC at 25 RPM to 200 volts AC at 1728 RPM.
Input Speed Sensor (ISS)
The Input Speed Sensor (ISS) is a magnetic inductive pickup that relays information about the transaxle input speed to the PCM/TCM. The PCM/TCM uses this information to control line pressure, TCC apply and release, and transaxle shift patterns. This information is also used to calculate appropriate operating gear ratios and TCC slippage.
The ISS mounts on the transaxle case under the channel plate next to the drive sprocket. An air gap of 0.26 - 2.90 mm (0.010 - 0.114 inch) is maintained between the sensor and teeth of drive sprocket. The sensor consists of a permanent magnet surrounded by a coil of wire. As the drive sprocket is driven by the turbine shaft, an AC signal is induced in the ISS. Higher vehicle speeds induce a higher frequency and voltage measurement at the sensor.
Sensor resistance should be 625 - 725 ohms when measured at 20°C (68°F). Output voltage will vary with speed from a minimum of 0.5 volts AC at 550 RPM, to 200 volts AC at 7000 RPM.
Transaxle Fluid Pressure (TFP) Switch Assembly
The Transaxle Fluid Pressure (TFP) switch assembly is attached to the control valve body. This assembly contains three fluid pressure switches and the Transaxle Fluid Temperature (TFT) sensor.
Two of the fluid pressure switches are normally open. These are used to indicate the position of the manual valve. The PCM/TCM uses this information to control line pressure, TCC apply and release and shift solenoid operation.
The TCC pressure release switch is used as a diagnostic tool to confirm that TCC is actually OFF when it has been commanded OFF by PCM/TCM. This switch is normally closed.
Each fluid pressure switch produces either an open or a ground to the PCM/TCM depending on the presence of fluid pressure at switches. The sequence of open and closed switches produces a combination of voltage readings. The PCM/TCM monitors these readings.
The PCM/TCM measures TFP switch signal voltage from each pin to ground and compares voltage to a TFP switch combination table stored in PCM/TCM memory. If PCM/TCM does not recognize TFP switch sequence, a diagnostic code will be set as a result. A diagnostic code may also set if the TFP switch sequence indicates a gear range selection that conflicts with other sensor inputs to the PCM/TCM.
TFP Switch Chart
Valid combinations for circuits B (1225) and C (1226) are shown in table. ON means that the switch is grounded with a resistance less than 50 ohms at 0 volts; OFF means that switch is open with a resistance greater than 50 ohms at 12 volts.
Park/Neutral Position (PNP) Switch
The PNP switch is located on top of the transaxle. The transaxle range switch contains multiple switches, four of which are used to create a coded signal to the PCM/TCM indicating gear selection. The coded signal can be viewed on the Scan tool as TR Switch -P/A/B/C and gear position indicated can be viewed as transaxle Range. The different combinations of the four PCM/TCM inputs, P/A/B/C, represent selections from Park to 1st or Invalid/Grounded/Open. Refer to table below.
On a vehicle equipped with a 2.2L, switches are all attached to ground on one side. When the switch closes, the PCM input is pulled low (ON). When switch is open input reads high (OFF). On vehicles equipped with a 3.0L, all switches are connected to ignition voltage on one side. When the switch closes, the TCM input is pulled high (ON). When switch is open the input reads low (OFF).
