SEAL 8N5763 - Caterpillar

System Operation Description:Use this procedure to troubleshoot the electrical system if a problem is suspected with the throttle position sensor or if the diagnostic code in Table 1 is active or easily repeated.
Table 1
Diagnostic Codes Table
Code and Description Conditions which Generate this Code System Response
91-8 Throttle Position Sensor : Abnormal Frequency, Pulse Width, or Period The Electronic Control Module (ECM) detects an incorrect frequency on the throttle signal or an incorrect duty cycle on the throttle signal. The frequency is below 150 Hz or the frequency in above 1000 Hz. The duty cycle is less than 5 percent or the duty cycle is greater than 95 percent. The code is logged. The ECM flags the throttle position as invalid data and a default value of zero percent is used. The engine speed is limited to low idle. Terminal BN on the customer connector provides the primary throttle signal to the engine's ECM. The throttle signal should be a 500 Hz constant frequency signal with a pulse width that varies with the throttle signal. This output signal is referred to as a Pulse Width Modulated signal (PWM).The throttle signal's duty cycle should be between 5 percent to 10 percent at low idle and 90 percent to 95 percent at high idle. The percent duty cycle is translated in the ECM into the throttle position of 0 percent to 100 percent. Use this procedure to troubleshoot an active diagnostic code of 91-8 Throttle Position signal abnormal.
Illustration 1 g01340700
Typical example
Illustration 2 g01345854
Illustration 3 g00725481
Throttle Position Versus PWM Input
Illustration 4 g01340702
Terminal locations for the G-C6/F-C2/F-C1/A-C92 Connectors for a RH Control panel and G-C6/F-C2/F-C1/C-C17 Connectors for a LH Control panel and the connectors
(Terminal 16) +Battery to local speed control
(Terminal 34) Digital return
(Terminal 39) Throttle signal
Illustration 5 g01328305
Terminal locations for the following connectors P-C2/A-C91 Connector for the power distribution panel, A-C2/J-C2 RH rigid harness connectors and C-C2/J-C1 LH rigid harness connectors.
(Terminal L) +Battery to local speed control
Illustration 6 g01340834
Terminal locations for the TB-C1/C-C18 customer connector
(Terminal BN) Customer's speed control
Illustration 7 g01340736
Terminal locations for the A-C1/E-C2 RH rigid harness connectors and C-C1/E-C1 LH rigid harness connectors
(Terminal a) Digital return
(Terminal AY) Throttle signal
Illustration 8 g01340838
P1 ECM connector
(P1-5) "Digital sensor return (LH)"
(P1-10) Throttle signal
Illustration 9 g01337991
Connector locations
(1) A-C1/E-C2 RH rigid harness connectors
(2) A-C2/J-C2 RH rigid harness connectors
(3) P-C1/A-C90 Connectors for the power distribution panel
(4) P-C2/A-C91 Connectors for the power distribution panel
(5) G-C6/F-C2/F-C1/A-C92 Connectors for a RH Control panel
(6) C-C22 Connection for the P2 ECM connector
(7) C-C15 Connection for the P1 ECM connector
(8) G-C6/F-C2/F-C1/C-C17 Connectors for a LH Control panel
(9) C-C18/TB-C1 Customer connectors
(10) C-C2/J-C1 LH rigid harness connectors
(11) C-C1/E-C1 LH rigid harness connectors Test Step 1. Inspect the Electrical Connectors and the Wiring
Turn the Engine Control Switch (ECS) to the OFF/RESET position.
Thoroughly inspect the ECM connector J1/P1. Inspect the wiring and the connectors that are associated with the circuit. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
Perform a 45 N (10 lb) pull test on each of the wires in the ECM connectors that are associated with the circuit.
Check the ECM connector (allen head screw) for