0787066 JOHNSON SERVICE MANUAL - ENGINE

Illustration 1 g01193730
Mounting location of the throttle position sensor on the throttle pedal (typical example)
The throttle position sensor is mounted to a pedal assembly that allows the operator to control the speed of the engine. The geometry of the pedal assembly controls both the travel of the sensor and the range of the output signal. The throttle position sensor cannot be adjusted.The output from the throttle position sensor is a PWM signal that varies with the position of the throttle pedal. The throttle position sensor produces a minimum duty cycle in the released position and a maximum duty cycle in the fully depressed position. When the pedal is released, the ECM translates the sensor's output signal to a throttle position of 0 percent. When the pedal is fully depressed, the ECM translates the output signal to a throttle position of 100 percent.The throttle position sensor is powered by 8.0 0.4 VDC that is provided by the ECM. A digital return for the sensor is also provided by the ECM.The ECM uses an automatic calibration function that allows the ECM to minimize the deadband of the sensor. The automatic calibration function assumes a range of PWM duty cycle at powerup. If the duty cycle of the sensor exceeds this initial range, the automatic calibration function adjusts the limits of the duty cycle in order to adjust for the new range.
Illustration 2 g01214470
Schematic for throttle position sensor
Test Step 1. INSPECT THE ELECTRICAL CONNECTORS AND THE WIRING
Turn the keyswitch to the OFF position.
Illustration 3 g01167488
Location of the J1/P1 ECM connectors (typical engine view)
(1) J1/P1 ECM connectors
Illustration 4 g01213916
Location of the engine interface connectors (typical left side engine view)
(2) engine interface connectors
Thoroughly inspect connectors (1) and (2). Also, thoroughly inspect the connector for the throttle position sensor. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
Illustration 5 g01214474
P1 ECM connector
(P1-4) 8 VDC supply
(P1-5) Digital return
(P1-66) Throttle position
Illustration 6 g01214475
Terminal locations at the engine interface connector for the throttle position sensor
(Terminal 33) 8 VDC supply
(Terminal 34) Digital return
(Terminal 35) Throttle position
Illustration 7 g01159881
Terminal locations for the throttle position sensor
(Terminal A) 8 V supply
(Terminal B) Digital return
(Terminal C) Throttle position
Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector and the connector for the throttle position sensor.
Check the allen head screw from each ECM connector for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque value.
Check the harness and the wiring for abrasion and for pinch points. Expected Result:All of the connectors, pins and sockets are completely coupled and/or inserted and the harness and wiring are free of corrosion, of abrasion and of pinch points.Results:
OK - The harness and connectors appear to be OK. Proceed to Test Step 2.
Not OK - The connectors and/or wiring are not OK.Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Ensure that all of the seals are properly in place and ensure that the connectors are completely coupled.Verify that the repair eliminates the problem.STOPTest Step 2. INSPECT THE THROTTLE PEDAL ASSEMBLY
Inspect the throttle pedal assembly for components that are loose, bent, missing, or worn.
Slowly depress the pedal and release the pedal. Expected Result:The throttle pedal assembly operates smoothly without excessive drag. The pedal springs back smoothly to the LOW IDLE position without assistance.Results:
OK - The throttle pedal assembly functions properly. The throttle pedal assembly is OK. Proceed to Test Step 3.
Not OK - The throttle pedal assembly is in poor repair.Repair: There is excessive drag or improper operation of the throttle pedal assembly. Repair the throttle pedal assembly or replace the throttle pedal assembly, as required.STOPTest Step 3. CHECK THE STATUS FOR "THROTTLE POSITION" ON CAT ET
Connect the Caterpillar Electronic Technician (ET) to the service tool connector.
Turn the keyswitch to the ON position.
Observe the status for "Throttle Position" on Cat ET while you operate the throttle pedal through the entire range of travel. Expected Result:The status is zero percent when the throttle pedal is released. The status progressively increases to 100 percent when the throttle pedal is fully depressed.Results:
OK - The throttle position sensor is working properly.Repair: The original problem seems to be resolved. There may be an intermittent electrical problem with the harness or the connectors. Refer to Troubleshooting, "Electrical Connectors - Inspect" if the problem is intermittent.STOP
Not OK - The throttle position that is displayed on Cat ET is questionable. Proceed to Test Step 4.Test Step 4. CHECK THE SUPPLY VOLTAGE AT THE SENSOR
Turn the keyswitch to the OFF position.
Disconnect the harness connector for the throttle position sensor.
Turn the keyswitch to the ON position.
Measure the voltage across terminal A (8 V supply) and terminal B (digital return) on the harness side of the connector.
Turn the keyswitch to the OFF position. Expected Result:The supply voltage measures 8.0 0.4 VDC at the sensor connector.Results:
OK - The correct voltage is measured at the sensor connector. The sensor is receiving the correct supply voltage. Proceed to Test Step 5.
Not OK - The voltage is not correct at the sensor connector.Repair: There m