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5B.7
Section 5B
EFI Fuel System
5B
Mounted on the throttle body/intake manifold and
operated directly off the end of the throttle shaft, the
TPS works like a rheostat, varying the voltage signal to
the ECU in direct correlation to the angle of the throttle
plate. This signal, along with the other sensor signals,
is processed by the ECU and compared to the internal
preprogrammed maps to determine the required fuel
and ignition settings for the amount of load.
The correct position of the TPS is established and set
at the factory. Do not loosen the TPS or alter the
mounting position unless absolutely required by fault
code diagnosis or throttle shaft service. If the TPS is
loosened or repositioned the appropriate “TPS
Initialization Procedure” (pages 5B.8-5B.10) must be
performed to reestablish the baseline relationship
between the ECU and the TPS.
Service
The TPS is a sealed, non-serviceable assembly. If
diagnosis indicates a bad sensor, complete
replacement is necessary. If a blink code indicates a
problem with the TPS, it can be tested as follows.
1. Counting the number of turns, back out the idle
speed adjusting screw (counterclockwise) until
the throttle plates can be closed completely.
2. Disconnect the main harness connector from the
ECU, but leave the TPS mounted to the throttle
body/manifold.
3. Connect the ohmmeter leads as follows:
(See chart on pages 5B.28, 5B.31, or 5B.32).
“35 Pin” (MA 1.7) Metal-Cased ECU: Red
(positive) ohmmeter lead to #12 pin terminal, and
Black (negative) ohmmeter lead to #27 pin
terminal.
“24 Pin” (MSE 1.0) Plastic-Cased ECU: Red
(positive) ohmmeter lead to #8 pin terminal, and
Black (negative) ohmmeter lead to #4 pin
terminal.
“32 Pin” (MSE 1.1) Plastic-Cased ECU: Red
(positive) ohmmeter lead to #8 pin terminal, and
Black (negative) ohmmeter lead to #4 pin
terminal.
Hold the throttle closed and check the resistance. It
should be 800-1200
ΩΩ
ΩΩ
Ω.
Figure 5B-6. Throttle Position Sensor Details.
General
The throttle position sensor (TPS) is used to indicate
throttle plate angle to the ECU. Since the throttle (by
way of the governor) reacts to engine load, the angle
of the throttle plate is directly proportional to the load
on the engine.
1
2
3
4
1. Throttle Valve Shaft
2. Resistor Track
3. Wiper Arm w/Wiper
4. Electrical Connection
Throttle Position Sensor (TPS)
Figure 5B-7. TPS Location.
Mounted Throttle
Position Sensor