Lit. No. 26473, Rev. 03 7November 1, 2007
ISOLATION MODULE TEST PROCEDURE – ALL MODULES
3. Turn ON the vehicle's parking lamps. Verify the
vehicle's parking lamps are ON.
4. Turn ON the vehicle's headlamps. Verify the
vehicle's low beams are ON.
5. Place the Isolation Module Tester PLOW
ATTACHED switch in the "ON" position. Verify the
vehicle's low beams go OFF and the following
Isolation Module Tester indicators are lit: PLOW
ATTACHED, plow PARK LIGHTS, and both plow
LOW BEAMs.
6. Place the vehicle's headlamps in the "high beam"
position. The Isolation Module Tester plow HIGH
BEAM indicators should light.
7. Turn ON the vehicle's left turn signal. Verify the
vehicle's left turn signal is functioning properly and
the Isolation Module Tester left TURN SIGNAL
indicator is lit. Turn OFF vehicle's left turn signal.
8. Turn ON the vehicle's right turn signal. Verify the
vehicle's right turn signal is functioning properly
and the Isolation Module Tester right TURN
SIGNAL indicator is lit. Turn OFF vehicle's right
turn signal.
9. Activate the vehicle's four-way flashers. Both the
vehicle's turn signal lamps and the Isolation
Module Tester TURN SIGNAL indicators should be
flashing. Turn OFF the vehicle's four-way flashers.
10. Place the Isolation Module Tester PLOW
ATTACHED switch in the "OFF" position. The
Isolation Module Tester HIGH BEAM, PARK LIGHTS
and PLOW ATTACHED indicators should go OFF
and the vehicle's high beams should be ON.
11. Place the vehicle in the DRL mode. Verify the
vehicle's DRLs are functioning properly.
NOTE: Due to the many DRL systems available, it is
the responsibility of the installer to fully understand
the operation of the system being tested.
12. Dedicated DRLs with a 26401, 27781 or 29070
Module: Place the Isolation Module Tester PLOW
ATTACHED switch in the "ON" position.
Depending on what module you have, the
following tester indicators should light:
26401 – HIGH BEAM (Dim)
27781 – LOW BEAM (Dim)
29070 – TURN SIGNAL
Low voltage DRLs with a 26400, 26401, 27781
or 29760-1 Module: Place the Isolation Module
Tester PLOW ATTACHED switch in the "ON"
position. The vehicle's DRLs should transfer to the
Isolation Module Tester. The Isolation Module
Tester mimics the vehicle's DRLs when the PLOW
ATTACHED switch is in the "ON" position.
13. Return the Isolation Module Tester PLOW
ATTACHED switch to the "OFF" position. Place
the Isolation Module Tester POWER switch in the
"OFF" position. Turn the vehicle's ignition OFF.
The vehicle portion of the test is complete. If the
system passes, remove the Isolation Module
Tester from the vehicle.
If the system fails the vehicle portion of the test,
remove the adapter cable (PN 26472) from the
Isolation Module Tester cable. Unplug the vehicle
lighting harness from position 2 (4-port) or
position A (3-port) of the Isolation Module. Connect the
Isolation Module Tester harness 2 to position 2 (4-port)
or position A (3-port) of the Isolation Module. Rerun
the vehicle portion of the test from the beginning to
determine if the vehicle lighting harness is functioning
properly. If it is, proceed to the module test section.
