1A-81 Engine General Information and Diagnosis:
3 1) Turn the ignition switch OFF.
2) Connect the ECM coupler and STP sensor coupler.
3) Disconnect the STVA lead wire coupler. Refer to “DTC
“C28” (P1655): Secondary Throttle Valve Actuator
(STVA) Malfunction (Page 1A-71)”.
4) Insert the needle point probes to the lead wire coupler.
5) Turn the ignition switch ON.
6) Measure the STP sensor output voltage at the coupler
(between the Y wire (+) and B wire (–)) by turning the
secondary throttle valve (close and open) with your
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. 0.5 V
Secondary throttle valve is opened: Approx. 3.9 V
((+) terminal: Y – (–) terminal: B)
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 “ECM
Removal and
Installation in Section
1C (Page 1C-2)”.
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-8)”.
Step Action Yes No
V
(A)
(B)
I823H1110070-01
I705H1110071-01
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