Speed Control (Pwm) - Test - Perkins M190C Troubleshooting Manual

196
Troubleshooting Section
Test Step 11. Check for a Short Circuit in
the Return Wire
Electrical shock hazard. The electronic unit injec-
tor system uses 67-73 volts.
A. Turn the keyswitch to the OFF position. A strong
electrical shock hazard is present if the keyswitch
is not turned OFF.
B. Disconnect the connector P2 from the ECM.
C. Locate the terminal for the supply of the faulty
injector in the connector P2. Measure the
resistance from the terminal to the engine ground
stud.
Expected Result:
The resistance is greater than 10 Ohms.
Results:
• OK – The resistance is greater than 10 Ohms.
Repair: Reconnect connector P2.
Replace the faulty injector.
Perform the "Injector Solenoid Test".
Use the electronic service tool in order to clear all
logged diagnostic codes and then verify that the
repair eliminates the fault.
STOP.
•
Not OK – There is a short in the return line.
Repair: Disconnect the connectors from the valve
cover base.
Measure the resistance of the return wire between
connector P2 and the engine ground stud.
If the resistance is less than 10 Ohms, the fault is
in the return wire between the ECM and the valve
cover base.
If the resistance is greater than 10 Ohms, the fault
is in the return wire under the valve cover.
Repair the injector harness or replace the injector
harness.
Use the electronic service tool to clear all logged
diagnostic codes and then perform the "Injector
Solenoid Test" in order to verify that the repair
eliminates the fault.
STOP.

Speed Control (PWM) - Test

System Operation Description:
The use of a Throttle Position Sensor (TPS)
eliminates the need for a mechanical throttle and
governor linkages. The TPS converts a lever
movement by the operator into an electrical signal.
The electrical signal is sent to the engine's Electronic
Control Module (ECM). The ECM processes the
signal in order to control the engine speed.
A Pulse Width Modulated signal (PWM) is created
by the TPS. The duty cycle varies with the throttle
position. The signal has a low duty cycle when the
throttle is at low idle. The signal has a high duty cycle
when the throttle is at high idle.
Illustration 81
Duty cycle versus throttle position
The signal that is produced by the TPS has a
variable frequency. The frequency of the signal must
be between 150 Hz and 1050 Hz or the ECM will
activate an -08 diagnostic code. Use this procedure
to troubleshoot these diagnostic codes:
• 91-08 Throttle Position signal abnormal
• 774-08 Secondary Throttle Position signal
abnormal
KENR9126
i04012490
g01122143