JLG 510AJ Service Manual - Manual (Page 147)

SECTION 3 - CHASSIS AND TURNTABLE
3121181 – JLG Lift – 3-105
DTC 122- TPS1 Signal Voltage Low
• Throttle Position Sensor 1
• Check Condition-Key On, Engine Off
• Fault Condition-TPS1 sensor voltage lower than the limit
defined in the diagnostic calibration
• Corrective Action(s): Sound audible warning or illuminate
secondary warning lamp, shutdown engine
• Non-emissions related fault
In the case of a diesel engine, an actuator controls a fuel injec-
tion pump, directly affecting the fueling level into the cylin-
ders. This may be by direct manipulation of the fuel injection
pump rack or by manipulation of the mechanical governor
control level or "throttle arm." In the DGC ECM and EDIS, refer-
ences to the throttle and throttle position sensor refer to these
fuel injection pump control actuators and their position feed-
back sensors. When the fuel injection pump is electronically
controlled it can be used to control the idle stability and limit
engine speed based on operating conditions.
The Throttle Position Sensor uses either;
1) a variable resistor and voltage divider circuit or
2) a non-contact hall-effect sensor to determine throttle actu-
ator position, and is located within the throttle actuator.
There are two types of throttle actuators;
1) actuator with analog position feedback and
2) actuator with digital position feedback
The first type, with analog position feedback, provides an ana-
log return signal between 0 and 5 volts that is proportional to
the throttle actuator position. The second type, with digital
position feedback, provides a serial data signal to the ECM
with the throttle actuator position voltage level encoded in
the data stream.
This fault will set if TPS1 voltage is lower than the low voltage
limit as defined in the diagnostic calibration at any operating
condition while the engine is cranking or running. The limit is
generally set to 4.90 VDC. In many cases, this condition is
caused by the TPS sensor being disconnected from the engine
harness, an open-circuit or short-to-ground of the TPS circuit
in the wire harness, or a failure of the sensor. This fault should
be configured to trigger an engine shutdown and the engine
will not start with this fault active.
2
16
13
12
1
5V_ext
Vs=+5 VDC
5V_rtn
TPS1
TPS SER +
+
-
Motor
DBW-
DBW+
ECM
H-Bridge
19
TPS SER -
Serial
xmitter
Electronic Throttle Actuator w/Analog Position Feedback Electronic Throttle Actuator w/Serial Position Feedback