Engine General Information and Diagnosis: 1A-86
4 1) Turn the ignition switch OFF.
2) Connect the ECM coupler and STP sensor coupler.
3) Move the air cleaner box backward. Refer to “Air
Cleaner Box Removal and Installation in Section 1D
(Page 1D-7)”.
4) Disconnect the STVA lead wire coupler. Refer to “DTC
“C28” (P1655): Secondary Throttle Valve Actuator
(STVA) Malfunction (Page 1A-75)”.
5) Insert the needle point probes to the lead wire coupler.
6) Turn the ignition switch ON.
7) Measure the STP sensor output voltage at the coupler
(between the (+) Y/W wire and (–) B/Br wire) by turning
the secondary throttle valve (close and open) with a
finger.
Special tool
(A): 09900–25008 (Multi-circuit tester set)
(B): 09900–25009 (Needle pointed probe set)
Tester knob indication
Voltage ( )
STP sensor output voltage
Secondary throttle valve is closed: Approx. 0.6 V
Secondary throttle valve is opened: Approx. 4.5 V
((+) terminal: Y/W – (–) terminal: B/Br)
Is the voltage OK?
• R, Y/W or B/Br wire
open or shorted to
the ground, or poor
11, 20 or 29
connection.
• If wire and
connection are OK,
intermittent trouble or
faulty ECM.
• Recheck each
terminal and wire
harness for open
circuit and poor
connection.
• Replace the ECM
with a known good
one, and inspect it
again. Refer to
“Engine Components
Removable with the
Engine in Place in
Section 1D
(Page 1D-5)”.
If check result is not
satisfactory, replace the
STP sensor with a new
one. Refer to “STP
Sensor Removal and
Installation in Section
1C (Page 1C-4)”.
Step Action Yes No
(A)
(B)
I718H1110201-03
I705H1110071-01
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