Type H: Negative (-) Multiplex - GM VSL 4000 Guide D'installation

type H: negative (-) multiplex

NOTE: A GM Resistor Interface Module (GM P/N 12496739) may be used for this type of door
locking system. If using a Resistor Interface Module, use the instruction guide provided with the
Resistor Interface Module for this type of door locking system.
The system is most commonly found in 1999 and newer Grand Am and Alero models, as well as 2000 and newer
Impala and Monte Carlo models. 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 resis-
tance 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 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.
IMPORTANT! The H2/A and H2/B wires are not required for wiring the door locks. For detailed
wiring instructions for these two wires, refer to the beginning of the Door Lock Harness (H2) Wire
Connection Guide section. Depending on the type of door lock system, there may be additional H2
harness wires that are not used for wiring the door locks.
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22 - English
NVSL4000