1987 Plymouth Horizon AutomaticFACTORY OEM SERVICE PROCEDURE

Code 17

  1. Connect diagnostic read-out box to engine harness connector. Place carburetor switch in "OPEN" position. Turn ignition switch to the "RUN" position. Place Read/Hold switch in the "Hold" position. Code 55 should be on the display of the read-out box.
  2. Connect a voltmeter to the Gray wire of the dual solenoid 3-pin connector and ground. Press and hold the ATM button until test code 97 appears on the display. Voltmeter should be pulsating and the solenoid clicking. If voltmeter pulsates between 0-1 volts, replace throttle control solenoid assembly. If voltmeter is not pulsating but reads within one volt of battery voltage, proceed to step 3). If voltmeter is not pulsating but reads 0-1 volt, turn ignition switch to the "OFF" position. Disconnect the computer 14-pin connector. Turn ignition switch to the "ON" position. If voltage is now within one volt of battery voltage, replace computer. If voltage is still 0-1 volt, repair Gray throttle control solenoid wire for short to ground.
  3. Turn the ignition off. Disconnect the computer 14-pin connector. Connect a voltmeter to the 14-pin connector cavity No. 6 and ground. Turn the ignition switch to the "RUN" position. If voltmeter reads within one volt of battery voltage, voltage is okay. Check terminal in connector cavity No. 6 to ensure it is not spread apart causing a poor connection. If connection is okay, replace the computer. If voltage is not okay, repair wire of cavity No. 6 for an open circuit to throttle control vacuum solenoid.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.

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