Vehicles with the 6.5L V8 turbo diesel engine powertrain also have the Hydra-matic 4L80-E automatic
transmission. The 4L80-E is a four-speed unit that uses a Transmission Control Module (TCM) to provide the following (refer to Figure 8-33):
• Control of shift timing (through solenoids A and B)
• Control of the TCC apply and release (through a PWM solenoid)
• Control of line pressure (through a variable force motor)
The automatic transmission control system uses two engine-mounted sensors to perform its functions. The first is the engine speed sensor, which is part of the oil pump drive mounted at the rear of the cylinder case (see Figure 8-34, view A). This sensor generates an alternating current signal with a frequency of four cycles per camshaft revolution.
The second input for automatic transmission control is the Throttle Position Sensor (TPS), mounted on the right side of the injection pump and operated by the rotation of the throttle shaft (see Figure 8-34, view B). This sensor has mounting slots, and an adjustment procedure must be performed during any service procedures that involve removal and installation of the TPS.
The adjustment procedure for the TPS has the following steps:
• Remove the intake manifold sound insulator cover.
• Install jumper wires between the TPS and vehicle wiring harness (see Figure 8-35, view A).
• Rotate the ignition switch to the RUN position.
• Measure the voltage between terminals A and C of the TPS connector, and multiply the measurement by 0.33 to obtain the desired TPS voltage.
Example: 5.05 volts times 0.33 equals 1.66 (plus or minus 0.01 volt).
• Install a gauge block (16.5mm [0.646-in.] thickness) between the injection pump throttle lever and the casting boss on the injection pump housing (see Figure 8-35, view B).
• Rotate the injection pump throttle lever so that the maximum speed stop screw holds the gauge block against the housing boss.
Note: Keep the throttle lever in this position during the remainder of the adjustment steps.
• Measure the voltage between terminals B and C of the TPS connector:
– If the measured voltage is within the calculated specification, reconnect the TPS and install the intake manifold sound insulator cover.
– If the voltage is not within the calculated specification, go to the next step.
• Loosen the TPS mounting screws and rotate it toward the rear of the vehicle (counterclockwise direction).
• With the voltmeter connected to terminals B and C of the TPS connector, rotate the TPS slowly toward the front
of the vehicle (clockwise direction) until the voltmeter indicates the correct voltage (1.65 to 1.67 volts, for example).
• Tighten the TPS mounting screws and confirm that the adjustment did not change.
• Reconnect the TPS and install the intake manifold sound insulator cover.