The VCM/PCM energizes the torque converter clutch pulse width modulated (TCC PWM) solenoid valve, which is located on the transmission valve body. The TCC PWM solenoid valve acts on the TCC apply valve in order to control the torque converter clutch application.

The TCC PWM Sol. Valve is pulse width modulated by the VCM/PCM. This means that the VCM/PCM pulses the solenoid so that the hydraulic pressure against the torque converter clutch modulates. This modulated pressure allows the TCC to slip slightly, thus keeping the TCC balanced just at the point of engagement.

One diagnostic code is associated with the TCC PWM solenoid valve Code P1860, TCC solenoid circuit - electrical, detects a fault in the TCC circuit. While Code P1860 is set, both fourth gear in hot mode and the TCC are inhibited. Shift adapts does not update and the MIL illuminates. Recovery can occur on the next ignition cycle.

The pressure control (PC) solenoid valve is attached to the valve body. The valve controls line pressure by moving a pressure regulator valve against spring pressure. The PC solenoid valve takes the place of the throttle valve or the vacuum modulator, which was used on past model transmissions.

The VCM/PCM varies line pressure based on engine load. Engine load is calculated from various inputs, especially the TP sensor switch. Line pressure is actually varied by changing the amperage applied to the PC solenoid valve from 0 amps (high pressure) to 1.1 amps (low pressure).

One diagnostic code is associated with the PC solenoid valve. Code P0748 sets when the VCM/PCM detects a difference of .16 amp or more between the amperage commanded and actual amperage. While the code is set, the PC solenoid valve turns OFF. Recovery can occur after the next ignition cycle. Code P0748 does not sense a hydraulic problem such as a stuck valve.

The 1-2 Shift Solenoid valve is attached to the valve body and is a normally open exhaust valve. The VCM/PCM activates the solenoid by grounding the solenoid through an internal quad driver. The 1-2 Shift Solenoid valve is ON in First and Fourth gear, but OFF in Second and Third gears. When ON, the valve redirects fluid to act on the shift valve. The 1-2 Shift Solenoid valve is usually black in color.

Two diagnostic codes are associated with the 1-2 Shift Solenoid valve: P0753 and P0751.

The first code is Code P0753 (1-2 Shift Solenoid Valve - electrical). The VCM/PCM continually monitors the 1-2 Shift Solenoid circuit for expected voltage. If the voltage reading is not what is expected, Code P0753 will be set. While Code P0753 is present, the VCM/PCM will default to maximum line pressure, freeze shift adapts from being updated and the MIL will not illuminate. Recovery can occur on the next ignition cycle.

Code P0751 (1-2 Shift Solenoid Valve - Performance) is set when the VCM/PCM detects First or Second gear at high speed. The VCM/PCM default action is Second gear only.

The 2-3 Shift Solenoid valve is attached to the valve body and is a normally open exhaust valve. The VCM/PCM activates the valve by grounding the valve through an internal quad driver. The 2-3 Shift Solenoid is ON in third and Fourth gear and OFF in First and Second gear. When ON, the valve redirects fluid to act on the shift valve. The 2-3 Shift Solenoid valve is usually white.

Two diagnostic codes are associated with the 2-3 Shift Solenoid valve: P0758 and P0756.

The first code is Code P0758 (2-3 Shift Solenoid Valve - electrical). The VCM/PCM continually monitors the 2-3 Shift Solenoid circuit for expected voltage. If the voltage reading is not what is expected, Code P0758 will set. While Code P0758 is present, TCC operation will be inhibited, line pressure will be set to maximum, and the transmission will default to Second gear only. Recovery can occur at the next ignition cycle.

Code P0756 (2-3 Shift Solenoid Valve - performance) will set when the calculated gear ratio is numerically higher than the gear commanded, which must be either Third or Fourth gear. The VCM/PCM default action is Second gear only.

A gear range sensing device call an Automatic Transmission Fluid Pressure Switch (TFP Val. Position Sw.) Assembly is used by the VCM/PCM in order to sense what gear range has been selected by the vehicle operator. The TFP Val. Position Sw. Assembly is located on the valve body and consists of five pressure switches combined into one unit. The VCM/PCM applies system voltage to the TFP Val. Position Sw. Assembly on three separate wires. These three circuits are either grounded or open, depending on which gear range has been selected, and on which combination of the five switches have pressure applied to them.

When the vehicle is in PARK, with the key ON and the engine OFF, the normal state of the TFP Val. Position Sw. Assembly will be Drive 2. When the key is ON and the engine is running, the normal state of the TFP Val. Position Sw. Assembly will be in PARK/NEUTRAL.

There are two possible combinations of the switches within the pressure switch manifold that do not represent an actual gear range. If the VCM/PCM detects either of these combinations for more that 0.5 seconds, Code P1810 will set. Code P1810 will not set, however, if a valid gear range combination appears at the wrong time.

While Code P1810 is present, the VCM/PCM will take the following actions:

If the TFP Val. Position Sw. Assembly resumes normal functioning, the transmission will resume normal operation after the next ignition cycle

Both of the Automatic Transmission Input(Shaft) Speed (A/T ISS) and the Automatic Transmission Output(Shaft) Speed (A/T OSS) Sensors are magnetic induction sensors. The input and the output sensors are accessible from the left hand side of the transmission. The A/T ISS Sensor is located just forward of center and the A/T OSS Sensor is located near the rear. A voltage signal is induced in the A/T ISS Sensor by serrations which are cut in the outside diameter of the forward clutch housing. Voltage is induced in the output sensor by gear teeth which are pressed on the outside diameter of the rear carrier assembly.

The VCM/PCM used speed information from these sensors in order to determine the following:

Type D code(s) P0502 (VCM) or P0722, P0723 (PCM) will set if a fault exists in the A/T OSS Sensor circuit, and the VCM/PCM will calculate a default value using the A/T ISS Sensor values. As long as the fault remains and the code is set, the VCM/PCM will also command maximum line pressure, freeze shift adapts, and the MIL will illuminate. If the fault is removed, normal operation will resume after the next ignition cycle.

For diesel engines, type B fault codes P0723 and P0724 will set.

The automatic transmission fluid temperature (TFT) sensor assembly is a thermistor which is mounted in the wiring harness assembly. Low transmission temperature produces high resistance, while high temperature produces low resistance. The VCM/PCM supplies a 5-volt signal to the TFT sensor assembly through an internal resistor. Then the VCM/PCM measures the voltage drop in the circuit. Voltage is high when the transmission is cold and low when the transmission is hot.

The VCM/PCM uses the TFT sensor assembly in order to regulate torque converter clutch apply, as well as shift quality.

DTCs P0711, P0712 and P0713 indicate a fault in the TFT Sensor Assembly circuit. After the vehicle has been started, transmission temperature should rise steadily and stabilize between 90°-115°C, depending on load. All three DTCs causes the VCM/PCM to use a default value of 140°C, thus reacting as if the transmission were hot in either case. When DTCs P0711, P0712 or P0713 are set, the VCM/PCM freezes the shift adapts from being updated, and the MIL illuminates. Some driveability symptoms will be noticed, especially when cold.