Cagiva Navigator, Workshop Manual, Page: 83 / 407

C.39
INJECTION - AIR INTAKE SYSTEM
“C21” IAT SENSOR CIRCUIT MALFUNCTION
PROBLEM
High temperature – air intake (low voltage – low resist-
ance)
Low temperature – air intake (high voltage – high re-
sistance)
POSSIBLE CAUSE
• Yellow/brown lead circuit in short-circuit to Earth.
• Black/brown lead circuit open.
• IAT sensor malfunction.
• ECM malfunction.
CHECK
• Remove the fuel tank as described in Chapter B.
1
Turn the ignition switch to the OFF position.
Check to see if the contacts of the IAT sensor connector are
loose or ruined.
If OK, measure the voltage of the IAT sensor at the wiring
coupling.
Disconnect the connector and turn the ignition switch to the
ON position.
Measure the voltage between the terminal of the yellow/brown
lead and the terminal of the black/brown lead.
IAT sensor voltage:
4.5-5.5V
(+yellow/brown –Earth)
(+yellow/brown –black/brown)
Tester dial indication: Voltage ( — )
NO ECM connector contacts loose or ruined.
Yellow/brown lead circuit or black/
YES brown lead circuit open or in short-circuit.
2 Turn the ignition switch to the OFF position.
Measure the resistance of the IAT sensor.
IAT sensor resistance: 2,2-2,7 k
Ω
at 20°C
(Terminal - Terminal)
Tester dial indication: Resistance (
Ω
)
NO
Substitute the IAT sensor.
YES
Yellow/brown lead circuit or black/brown lead circuit open or in short-
circuit to Earth. Or the connections 12 or 24 are ruined (see page
C-6). If the leads and connections are OK, the problem is intermit-
tent or the ECM is defective.
Recheck each terminal and the wiring for open circuits or ruined
connections.
Substitute the ECM sensor and
recheck.
Engine coolant
Resistance
temperature
20°C Approx. 2,45 K
Ω
50°C Approx. 0,811K
Ω
80°C Approx. 0,318 K
Ω
110°C Approx. 0,142 K
Ω
…
The method of measuring the resistance
of the IAT sensor is the same as the
method utilised for the ECT sensor (see
page C-43 for details).
Black/Brown
Yellow/Brown
ECM connectors
24
12