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4-70 FI SYSTEM DIAGNOSIS
“C29” (P1654-H/L) STP SENSOR CIRCUIT MALFUNCTION
INSPECTION
Step 1 (When indicating C29:)
1) Turn the ignition switch OFF.
2) Lift and support the fuel tank. (5-3)
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 R wire A and ground.
7) Also, measure the voltage at the R wire A and B/Br wire C.
STP sensor input voltage: 4.5 – 5.5 V
(+ R – - Ground)
(+ R – - B/Br)
09900-25008: Multi-circuit tester set
Tester knob indication: Voltage ()
Is the voltage OK?
DETECTED CONDITION POSSIBLE CAUSE
C29 Signal voltage is not within the following
range.
Difference between actual throttle open-
ing and opening calculated by ECM is
larger than specified value.
0.15 V Sensor voltage < 4.85 V
• STP sensor maladjusted
• STP sensor circuit open or short
• STP sensor malfunction
• ECM malfunction
P1654
H
Sensor voltage is higher than specified
value.
• STP sensor circuit shorted to VCC or ground cir-
cuit open
• STP sensor circuit open or shorted to ground or
VCC circuit open
L
Sensor voltage is lower than specified
value.
YES Go to Step 2.
NO
• Loose or poor contacts on the ECM coupler
(terminal A or S)
• Open or short circuit in the R wire or B/Br wire
ECM
E2
VCC
Y/W
R
STP
STP sensor
B/Br
Y
B
BI
1
1
V