Hyundai Coupes/Sedans 1986-1993 Repair Guide

Control Unit Functions

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See Figures 1, 2, 3 and 4

EXPLANATION



Set (Fixed Speed Control)

With the main switch turned to the ON position, the set switch is switched from ON to OFF position while the vehicle is being driven within the speed range in which the speed settings are possible (approximately 25-90 mph). The vehicle speed at the moment the set switch was switched from ON to OFF is memorized as the set vehicle speed and there after the actuator is controlled so that fixed speed driving at that speed is possible.

Initial Pulse

The initial pulse opens the throttle valve to a degree of opening which approximately corresponds to the vehicle speed. This pulse is output when the cruise control system is set.

Trim Pulse

The trim pulse is a control pulse for correcting the vehicle speed which is output response to detect speed errors. The output pulse width is determined based on the amount of deviation between the current vehicle speed and the set vehicle speed and on throttle position.

Coast

During fixed speed driving, while the coast switch is ON , the actuator D.C. motor is caused to rotate to the rel (release) side. The vehicles speed when the switch is OFF as deceleration continues is entered in the memory, and thereafter controlled as a fixed speed.

Resume Speed

When (after the cruise control system is canceled by the cancel conditions) the resume switch is switched from OFF to ON , while driving at a vehicle speed which is the low speed limit (approximately 25 mph) or higher, the vehicle speed memorized before cancellation of the cruise control system will be controlled as the fixed speed.

Acceleration

During fixed speed driving or above the low speed limit, while the acceleration switch is ON , the actuator's D.C. motor is caused to rotate to the pull side. The vehicle speed when the switch is OFF as acceleration continues is entered in the memory and is thereafter controlled as the fixed speed.

Cancellation

When the signals below are input (during fixed speed driving), conductivity to the electromagentic clutch is interrupted, thus canceling the cruise control system:

  1. Brake lamp switch ON (brake pedal depressed).
  2.  
  3. Inhibitor switch ON (selector lever at the P or N position).
  4.  
  5. Clutch switch ON (clutch pedal depressed).
  6.  

When the brake pedal is depressed and the brake lamp switch is switched ON, the cruise control system will be canceled even if there is wiring damage or disconnection at the fuse for the brake lamp.

Low Speed Limit

There is automatic cancellation at or below the low speed limit (approximately 25 mph).

High Speed Limit

The vehicle cannot be driven at a fixed speed which is at or higher than the high speed limit (approximately 90 mph). Note that the vehicle speed memorized when the set switch is pressed while the vehicle is traveling at the high speed limit or higher will be the high speed limit vehicle speed.

Automatic Cancellation

When, during fixed speed driving, the signals described below are input, conductivity to the electromagnetic clutch is interrupted, thus canceling the cruise control system.

  1. If the vehicle speed decreases to a speed which is approximately 12 mph or more below the memorized vehicle speed.
  2.  
  3. If there is no input of the vehicle speed signal for more than 0.5 second.
  4.  
  5. If there is damaged or disconnecting wiring of the input line (brake lamp switch load side) of the brake lamp switch.
  6.  
  7. If the cancel switches (brake lamp switch, inhibitor switch, and clutch switch) and command switches (set switch or resume switch) are switched on at the same time.
  8.  

If the set and resume switches are ON at the same time, the cruise control will operate in the coast mode and the speed will decreases.

Piezo Alarm

When the cruise switch is ON , the set switch or resume switch ON signals are received, the alarm is activated for approximately 0.2 seconds. Be sure to note the power is supplied from fuse 13 (10 amp) on Excel and fuse 8 (10 amp) on Sonata, to the alarm.

Accelerator Switch

The accelerator switch is a switch that functions to detect the condition of the accelerator pedal and is one of the ELC 4 automatic transaxle sensors. Because the accelerator pedal is not used during fixed speed driving, the accelerator switch is OFF during this time only, so as not to adversely affect the functions of the ELC 4 automatic transaxle.



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Fig. Fig. 1: Cancel function of speed control system

Overdrive Cancel Function

When, during fixed speed driving, the actual vehicle speed decreases to (or below) a speed which is below memorized vehicle speed and the actual vehicle speed continues at that reduced speed or during the resume operation or the acceleration operations that have already been described, it becomes necessary to return to the vehicle speed for a short period of time and to accelerate, the overdrive function of the ELC 4 automatic transaxle equipped vehicles is canceled for a certain time.



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Fig. Fig. 2: Overdrive function of speed control system

Self Diagnosis Function

The cruise control system can display trouble codes from the cruise control unit through the diagnostic connector. The codes can be read by using a voltmeter or a multi-use tester. Be sure to turn the main switch ON before trying to read the codes.

The display of the trouble codes starts if the vehicle speed decreases to less than approximately 12 mph after the cancellation of the cruise control system function and stops if the vehicle speed increases to approximately 12 mph or higher.

Input Switch Check

The unit has a check function for the input signal switch. The display starts when the main switch is turned ON while the set and resume switches are turned to the ON position.

  1. Trouble codes are stored in memory and display in sequential order of priority.
  2.  
  3. Smaller code numbers shall be placed higher in priority.
  4.  
  5. Even when a input of higher priority is detected among check function items, an item currently in stored in memory shall be shown on display for one cycle (one cycle shall be an interval during which all checked functions stored in memory are shown on display).
  6.  
  7. Code number 24 and 25 should be checked while the vehicle is running.
  8.  



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Fig. Fig. 3: Self-diagnostic codes-speed control system



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Fig. Fig. 4: Self-diagnostic codes-speed control system (continued)

 
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