© 2002 Cannondale Corporation - All Rights Reserved
14
Electrical_EFI Service Manual.fm
Static Test - Resistance
1. Disconnect the sensor harness connector.
2. Use an Ohmmeter to measure the sensor resis-
tance between terminals 1 and 2.
SERVICE:
Crankshaft position sensor
resistance range - 532 TO 588
Ohms
IDLE AIR CONTROL VALVE (IACV)
The Idle Air Control Valve (IACV) is an ECU con-
trolled valve mounted on the throttle body.
As soon as the ECU is powered up, this valve
begins to move to the correct position (increasing or
decreasing the available air bypass volume needed
for cold start). The ECU controls the valve arm
depending on engine temperature. The valve arm
moves in “steps” that extend or retract the valve arm
inside the bypass housing.
The arm travels.024mm per step.
Total travel = 0 to 255 steps
In a cold engine, the valve opens (arm retracts)
allowing more air to bypass the throttle plate. As the
engine warms up, the valve closes (arm extends)
until the bypass channel through the housing is com-
pletely shut at 60°C.
Here are some symptoms of a faulty IACV
•
Hard starting - the valve arm could be stuck
shut. In this case, the extra air needed for cold
starting conditions is not available. Enough air
may be available to start a warm.
•
Engine idles too fast - valve is stuck open.
•
Rough idle - if the valve arm is malfunctioning
Dynamic Test 1 - ECU Monitor
1. Make sure the engine is completely cool.
2. Use the Cannondale Diagnostic and Maintenance
Tool to read current valve stepped position with
the cool engine.
Read the valve position at IACV Stepper Position
field in the ECU Monitor window. Refer to "Using
the ECU Monitor" starting on page 39.
NOTE :
Make sure the monitor is in “continuous” mode.
3. Start the engine and allow to it idle normally.
Observe the IACV Stepper Position and Engine
Temperature (degC) fields. As the engine temper-
ature climbs, the IACV Stepper Position should
increase indicating that the arm is extending and
the bypass channel inside the housing reducing.
At engine operating temperature (60°C) the arm
should be fully extended and the bypass closed.
4. If no change is observed, go to Dynamic Test 2.
Dynamic Test 2 - Confirm arm movement
1. Make sure the vehicle engine is completely cool
and press the engine stop button to ensure that
the ECU is powered down.
2. Remove the bypass housing from the throttle
body with the IACV valve attached to it.
1. Idle Air Control Valve (IACV)
IACV Stepped positions
Fully Open
Fully Closed (at 60°C)
175
205
1
