872786 Volvo.Penta Aquamatic drive

Table 1
Diagnostic Codes Table    
Code    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 duty cycle on the throttle signal. The duty cycle is less than 5 percent or the duty cycle is greater than 95 percent.
or
The throttle signal is outside the range of 1.228 kHz 150 Hz.     The code is logged. The ECM flags the throttle position as invalid data. The desired engine speed is set to the last valid speed signal that was recognized by the ECM.
   The throttle switch provides the operator with the ability to select the desired engine speed. The throttle switch is a rotary switch with ten positions and four outputs. The throttle switch is connected to four inputs on the machine control module. The machine control module interprets the signals from the throttle switch as a throttle command. The machine control module then outputs a throttle signal to the engine's ECM. The throttle signal is referred to as a duty cycle or as a PWM signal. The throttle signal is valid when the following conditions exist:
The duty cycle is between 5 percent and 95 percent.
The PWM signal is 1.228 kHz 150 Hz.If the ECM detects an abnormal throttle signal, the ECM will generate a diagnostic code. If a diagnostic code is active for the throttle signal, the ECM ignores the throttle signal and the desired engine speed is set to the last valid speed that was recognized by the ECM. When