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.Flywheel has 54 teeth under the flywheel ring gear which the crank position sensor uses
to provide engine rpm and crankshaft position information the ECM