Neutral Control

When a vehicle is stopped in "D" and the brakes applied, the AF 17 will go to the neutral condition releasing the forward clutch (C1) will engage, the transmission will be in 1st gear and creep force will occur again.

If the vehicle is stopped on an upslope, creep force does not operate because of neutral condition by the Neutral control. Therefore the TCM operates the 2nd and 4th clutch brake (B1) and keeps the equivalent force to creeping force. This is called the "Hill Hold" function.

If the TCM detects steep upslope by decreasing of acceleration, Neutral control does not operate.

The TCM directly controls the forward clutch (C1) by the linear solenoid function of the Line Pressure Control Solenoid Valve Assembly (SLT).

When vehicle is operated in the Winter mode, the TCM implements Neutral control by keeping the AF 17 in 3rd gear, engages the over drive clutch (C0) and operates the Hill Hold function.

Neutral control does the following 3 processes:

1. C1 release control
2. C1 neutral control (keep in neutral)
3. C1 apply control

• C1 release control

  The TCM detects a stopped vehicle due to RPM change in the C1. Oil pressure is released and the C1 clutch disengages smoothly.

  The TCM operates the Hill Hold function after sends signal to turn ON the 1-2/3-4 Shift Solenoid Valve Assembly S2 (316), and engages the 2nd and 4th clutch brake ((B1). The releasing time of the C1 is learned by varying the C1 piston stroke.

• C1 in neutral control

  This control applies the C1 clutch with the Line Pressure Control Solenoid Valve Assembly (SLT) by switching on the neutral switching solenoid SN (301) and keeps neutral control moderately during neutral. This control decreases the load of the C1 clutch and prevents delay in re-engagement.

• C1 apply control

  This control applies C1 pressure smoothly and C1 clutch is engaged moderately when brake pedal is release. It releases the B1 and cancels the Hill Hold function. The control then switches off the S2 and SN to be able to start driving in 1st gear.

• Self Diagnosis

  The TCM constantly monitors the sensors, solenoid valves and the other electrical parts to detect malfunctions. If a malfunction occurs in the system, the TCM turns on the SES light and sets a DTC.

• Backup Program

  When the TCM detects that a malfunction has occurred, all five solenoids will be turned off. The vehicle can then be driven to the nearest service facility by manual shifting the gears.