© 2000 Directed Electronics, Inc. Vista, CA
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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
