IGNITION
90-883728 JULY 2001 Page 2A-17
Throttle Position Sensor (TPS)
The TPS transmits throttle angle information to the ECM which varies the injector pulse
width accordingly. Should the sensor fail, the warning horn will sound. RPM will be re-
duced by the ECM. TPS settings are not adjustable. TPS settings can be monitored with
the Digital Diagnostic Terminal through the ECM. Voltage change should be smooth from
idle to wide open throttle. If voltage change is erratic, TPS is defective.
58899
a
b
c
d
a-Throttle Position Sensor (TPS)
b-Throttle Stop Screw
c-Roller
d-Pocket
Throttle Position Sensor Specifications
Idle 0.19 – 1.0 VDC
Wide Open Throttle 3.45 – 4.63 VDC
Throttle Position Sensor (TPS) Troubleshooting
If the throttle position sensor is out of the intended operating range when the engine is
started, the Electronic Control Module (ECM) will sense that the Throttle Position Sensor
(TPS) has failed. The warning horn will sound, check engine light will illuminate, DDT will
indicate failed TPS and the engine will go into RPM reduction. When the engine is started,
the throttle arm on the engine must be against the throttle stop screw. Do not move throttle
or fast idle control lever forward.
• Check throttle cable adjustment. The throttle stop screw on the throttle arm must be
against the throttle stop on the cylinder block when the engine is started. Pre-load the
throttle cable barrel 1 or 2 turns if necessary.
• Verify driver is not pushing on throttle (if foot throttle is used) or advancing the throttle
only on the control box.
• Check throttle cam to roller adjustment. If the roller is not down in the pocket/valley
area on the cam, there is a tendency for the roller to ride up or down on the cam which
causes the TPS link arm to push/pull on the TPS lever resulting in changing values.
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