Pontiac Fiero 1988 Service Manual page 615

6E3-A-32 DRIVABILITY
A N D
EMISSIONS
- FUEL
INJECTION (PORT)
THROTTLE
POSITION
SENSOR
IDLE
MOT .*
5-19-87
FRONT VIEW
OF CONNECTOR
TO COOLANT
SENSOR
ECM
' 452 BLK
417 BLU
416 GRY
TO MAP SENSOR
D t l D t l
_ L
— T P S SIGNAL
- W — 5 V R E F
C13
_ L
— T P S SIGNAL
- W — 5 V R E F
C13
_ L
— T P S SIGNAL
- W — 5 V R E F
C14
_ L
— T P S SIGNAL
- W — 5 V R E F
C14
_ L
— T P S SIGNAL
- W — 5 V R E F
_ L
— T P S SIGNAL
- W — 5 V R E F
5-8-87
* 5 S 1 9 1 0 - 6 E
CODE 21
THROTTLE POSITION SENSOR (TPS) CIRCUIT
(SIGNAL VOLTAGE HIGH)
2.8L "P" SERIES (PORT)
Circuit Description:
The throttle position sensor (TPS) provides a voltage signal that changes relative to the throttle blade.
Signal voltage will vary from about .5 at idle to about 5 volts at wide open throttle.
The TPS signal is one of the most important inputs used by the ECM for fuel control and for most of the
ECM control outputs.
Test Description:
Numbers below refer to circled
numbers on the diagnostic chart.
1. Code 21 will set if:
• Engine running less than 1600
• TPS signal voltage is greater than 2.5 volts.
• All conditions met for 2 seconds.
• MAP less than 70 kPa
With throttle closed the TPS should read less than
1.25 volts. If it does not replace TPS.
2. With the TPS sensor disconnected, the TPS
voltage should go low if the ECM and wiring are
OK.
3. Probing CKT 452 with a test light checks the 5V
return CKT, because a faulty 5V return will cause
a Code 21.
Diagnostic Aids:
A "Scan" tool reads throttle position in volts.
Should read less than 1.25 volts with throttle closed
and ignition "ON" or at idle. Voltage should
increase at a steady rate as throttle is moved
toward WOT.
An open in CKT 452 will result in a Code 21.
Refer to Intermittents in Section "B".