4-38 FI SYSTEM DIAGNOSIS
“C29” STP SENSOR CIRCUIT MALFUNCTION
INSPECTION
Step 1
1) Remove the air cleaner box. ("5-15)
2) Turn the ignition switch OFF.
3) Check the STP sensor coupler for loose or poor contacts.
If OK, then measure the STP sensor input voltage.
4) Disconnect the STP sensor coupler.
5) Turn the ignition switch ON.
6) Measure the voltage at the Red wire and ground.
7) If OK, then measure the voltage at the Red wire and B/Br
wire.
% STP sensor input voltage: 4.5 – 5.5 V
(
+ Red –
- Ground)
(
+ Red –
- B/Br)
! 09900-25008: Multi circuit tester set
' Tester knob indication: Voltage (()
Is the voltage OK?
DETECTED CONDITION POSSIBLE CAUSE
Signal voltage is out of the specified range.
Difference between actual throttle opening and
opening calculated by ECM in larger than specified
value.
0.1 V Sensor voltage 4.8 V
• STP sensor maladjusted.
• STP sensor circuit open or short.
• STP sensor malfunction.
• ECM malfunction.
1
1
V
1
V
YES Go to Step 2
NO
• Loose or poor contacts on the ECM coupler.
• Open or short circuit in the Red wire or B/Br
wire.
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