Pontiac Fiero 1988 Service Manual page 617

8E3-A-34 DRIVABILITY AND EMISSIONS FUEL INJECTION (PORT)
THROTTLE
POSITION
SENSOR
IDLE '
WOT ,
5-19-87
FRONT VIEW
OF CONNECTOR
ECSVI
TO COOLANT
SENSOR
0£i
' 452 BLK
417 BLU
416 GRY
TO MAP SENSOR
D12 D12
JL
— T P S SIGNAL
AMA— 5 V REF
JL
— T P S SIGNAL
AMA— 5 V REF
JL
— T P S SIGNAL
AMA— 5 V REF
C14
JL
— T P S SIGNAL
AMA— 5 V REF
C14
JL
— T P S SIGNAL
AMA— 5 V REF
JL
— T P S SIGNAL
AMA— 5 V REF
5-8-87
* 5 S 1 9 1 0 - 6 E
CODE 22
THROTTLE POSITION SENSOR (TPS) CIRCUIT
(SIGNAL VOLTAGE LOW)
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 22, will set if:
• Engine running
• TPS signal voltage is less than about .2 volt for
2 seconds
2. Simulates Code 21: (high voltage) If the ECM
recognizes the high signal voltage, the ECM and
wiring are OK.
3. This simulates a high signal voltage to check for
an open in CKT 417. The "Scan" tool will not read
up to 12 volts, but what is important is that the
ECM recognizes the signal on CKT 417.
4. There should be 5 volts at terminal "A" if
measured with a DVOM when ignition is "ON".
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 or short to ground in CKTs 416 or 417
will result in a Code 22.
Refer to Intermittents in Section "B".