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2. Connect the wiring harness to the ECU; then con-
nect the battery.
NOTE: Make sure all connectors are clean and
tight.
Throttle Position Sensor
If the snowmobile is under warranty, the throttle posi-
tion sensor on the EFI system is not a serviceable part.
If the sensor should malfunction, the complete throttle
body assembly must be replaced.
NOTE: If the snowmobile is in warranty, breaking
the seal on the idle screw jam nut or the Phillips-
head screws on the TPS will void warranty.
NOTE: A throttle body assembly with the same
symbol marking on the injectors as the ones being
replaced must be ordered. The symbol is located
on the side of the injector top.
Testing Throttle Position Sensor
When checking ignition timing, the timing light must
be connected to the number 1 spark plug wire (MAG-
side cylinder). If the number 2 cylinder spark plug wire
is used, the timing light may show a 2° error in ignition
timing when ignition timing is actually correct.
For example, the correct ignition timing is 12° ± 2°
BTDC at 2000 RPM.
To quickly check TPS operation, measure the timing
according to the chart; then disconnect the TPS wiring
and recheck the timing. A system with a functioning
TPS will show a change in the timing. This is known
as "Fail-Safe Ignition Timing" and is built into the sys-
tem to protect the engine should the TPS fail. If this
change is not seen, the TPS may have failed and must
be checked.
If the ignition timing isn't 12° ± 2° at 2000 RPM, the
TPS should be checked for proper adjustment using
the Throttle Position Sensor Adjustment Tool Kit and
a digital voltmeter.
Verifying TPS Adjustment Tool
Before using the TPS adjustment tool, verify its bat-
tery condition. The battery used in the tool is a 9-volt
battery. To check battery condition, use a digital volt/
ohmmeter set on DC volt scale. Test between the
adjustment tool black and red jacks. Insert the red lead
of the digital voltmeter into the red jack of the adjust-
ment tool and the black lead of the digital voltmeter
into the black jack of the adjustment tool. The green
power light of the analyzer should now be illuminated.
If voltage is found below 4.9 volts, replace the battery.
NOTE: The battery used in the tool is a 9-volt bat-
tery; also, the Test Harness must be plugged into
the analyzer for testing voltage.
Checking TPS
NOTE: Before using the TPS adjustment tool,
verify its battery condition.
1. Using Throttle Position Sensor (TPS) Adjustment
Tool Kit (p/n 3639-891), connect its wiring har-
ness to the TPS. Connect the red and black digital
voltmeter leads to the white and black jacks of the
TPS adjustment tool.
2. Ensure that the throttle cable/control rod has the
proper amount of free-play.
3. With the throttle in the idle position, compare the
reading on the voltmeter to the chart. If the reading
is within prescribed specification, proceed to step 4.
Idle Position
0.710-0.818
4. Compress the throttle lever slowly to the full-open
position. The meter reading should show a smooth
rise in voltage all the way to the full-open throttle
position. If the voltage seems to be erratic or
doesn't meet the prescribed specification, repeat
this procedure several times to confirm results.
5. If the full-open throttle voltage remains erratic or
out of specification; replace the throttle body
assembly.
6. If the TPS is within the prescribed specification, dis-
connect the adjustment tool harness from the TPS.
Connect the snowmobile TPS harness to the TPS.
NOTE: Before installing the TPS harness connec-
tor, apply dielectric grease to the connector pins.
Fail-Safe Ignition Timing
Engines equipped with throttle position sensor have a
protective feature called "fail-safe" ignition timing
preventing engine damage should the TPS fail. If the
TPS does fail, the engine will run normally at low
RPM but will run poorly at high RPM allowing the
operator to get the snowmobile to safety with little or
no engine damage.
NOTE: The engine will continue to operate this
way until the TPS is replaced.
Wide-Open Position
3.472-4.048
59
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