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© 2000 Directed Electronics, Inc. Vista, CA
The system is most commonly found in Ford, Mazda, Chrysler and GM vehicles. The door lock switch or door key
cylinder may contain either one or two resistors.
SINGLE-RESISTOR TYPE:
If one resistor is used in the door lock switch/key cylinder, the wire will pulse ground
in one direction and resistance to ground when operated in the opposite direction.
TWO-RESISTOR TYPE:
If two resistors are used in the factory door lock switch/key cylinder, the door lock
switch/key cylinder will read resistance to ground in both directions.
DETERMINING THE PROPER RESISTOR VALUES:
To determine the resistor values, the door lock switch/key cylinder
must be isolated from the factory door lock system. For testing, use a calibrated digital multimeter that is set to ohms.
IMPORTANT:
To ensure an accurate resistance reading, do not touch the resistor or leads during testing.
1. Cut the output wire from the door lock switch/key cylinder in half.
2. Test with the meter from the switch side of the cut door lock switch/key cylinder wire to a reliable ground
source. Some good ground references are the ground input source to the door lock switch/key cylinder or the
battery ground.
3. Operate the door lock switch/key cylinder in both directions to determine the resistor values. If the multi-
meter displays zero resistance in one direction, no resistor is needed for that direction.
4. Once the resistor value(s) is determined, refer to the wiring diagram for proper wiring.
type H: negative (-) multiplex
