Pontiac Fiero 1988 Service Manual page 489

6E2-A-34 DRIVEABILITY AND
E M I S S I O N S
- FUEL INJECTION (TBI)
THROTTLE
POSITION
SENSOR
THROTTLE
POSITION
SENSOR
CONNECTOR
TO MAP SENSOR
ECM
— 416GRA
417 DK BLU
452 BLK
W11
B19
B12
TO COOLANT SENSOR
5-5-87
' 5VREF
TPS SIGNAL
SENSOR
GROUND
4-29-87
* 7S 3206-6EA
CODE 2 2
THROTTLE POSITION SENSOR (TPS) CIRCUIT
(SIGNAL VOLTAGE LOW)
2.5L "P" SERIES (TBI)
Circuit Description:
The throttle position sensor (TPS) provides a voltage signal that changes, relative to the throttle valve.
Signal voltage will vary from less than 1.25 volts at idle to about 4.5 volts at wide open throttle (WOT).
The TPS signal is one of the most important inputs used by the ECM for fuel control and for many of the
ECM controlled outputs.
Test Description:
Numbers below refer to circled
numbers on the diagnostic chart.
1. This step checks to see if Code 22 is the result of a
hard failure or an intermittent condition.
A Code 22 will set if:
• The engine is running.
• TPS voltage is below .2 volts (200 mv).
2. This step simulates conditions for a Code 21. If a
Code 21 is set, or the "Scan" tool displays over 4
volts, the ECM and wiring are OK.
3. The "Scan" tool may not display 12 volts. The
important thing is that the ECM recognizes the
voltage as over 4 volts, indicating that CKT 417
and the ECM are OK.
4. If CKT 416 is shorted to ground, there may also be
a stored Code 34.
Diagnostic Aids:
A "Scan" tool displays throttle position in volts.
Closed throttle voltage should be less than 1.25 volts.
TPS voltage should increase at a steady rate as
throttle is moved to WOT.
An open, or grounded, 416 or 417 will result in a
Code 22.
If Code 22 is intermittent, refer to Section "B".