Section 5 Troubleshooting; Introduction; Theory Of Operation, Electronic Start Sequence - Kohler 24RCL Manual

5.1 Introduction

Corrective action and testing in many cases requires
knowledge of electrical systems and electronic circuits.
Have an authorized distributor/dealer or trained service
technician perform testing and service.
Refer to the engine service manuals for engine service
information. See the List of Related Materials for the
document part number.
If the troubleshooting procedures in this section identify
a failed part, refer to the parts catalog for replacement
part numbers. See the List of Related Materials in the
Introduction for the parts catalog number.
5.2 Theory of Operation,
Electronic Start Sequence
The following steps trace the electronic system as leads
and components are energized and fuel, ignition, and
engine crank are added during the start sequence. Use
the steps below and refer to the wiring schematics in
Section 8 to assist with troubleshooting and to check for
loose connections or damaged leads.
1. When the generator is not running:
a. 12 VDC battery power is provided to the fuse
and relay box (cooling fans), the RDC2
controller, and the ECM.
b. Accessories have power and communication
through the RBUS connections.
c. The battery charging circuit is energized and
charging.
d. The engine compartment temperature sensor
(ETCS) is energized and is sending signals to
the RDC2 controller.
2. Pressing the Run button on the RDC2 controller
energizes lead 70.
a. Lead 70 energizes the P15 relay.
b. The P15 relay closes the P15 contact, which
sends 12 VDC to the run circuit.
3. The run circuit, lead 70, sends 12 VDC to the K1
relay, fuel valves 1 and 2, the activator board, the
diagnostic plug (P28), and the ECM interface plug.
a. K1 relay energizes the cooling fan circuit.
Radiator fans (RF1 and RF2) start to run at low
speed (6 VDC).
b. The fuel valves open allowing fuel to flow to the
air-fuel mixer and throttle body.
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Section 5 Troubleshooting

c. Lead 70 also sends 12 VDC to the ECM on
inputs P26-3 (SW IGN) and P26--65 (ACTPWR
Diagnostic Feedback), ignition coil, fuel control
valve, battery charging alternator, and the O2
(HEGO) sensor.
(1) Once ECM is energized on input P26-3, the
ECM goes through the initialization
process and begins CAN communication
with the RDC2 controller (yellow and green
leads).
(2) Input on P26-65 indicates to the ECM that
the run relay is energized.
(3) During the initialization process, the ECM
initiates the 5-volt sensor circuit, lead 40,
and 12 VDC heater circuit for the O2
(HEGO) sensor, lead 82.
4. When CAN communication is established, the
RDC2 controller starts the cranking sequence by
energizing lead 71 with 12 VDC.
a. Lead 71 energizes P10 crank relay.
b. P10 crank relay closes the P10 contact which
energizes lead 16S.
c. Lead 16S energizes the starter solenoid. The
starter solenoid closes the start solenoid
contact, energizing the starter motor and
cranking the generator set.
d. Lead S1 signals the ECM on input P27--109
that the starter solenoid is energized.
e. As the engine begins to crank, the crank
position sensor sends a small AC signal
indicating speed sensing and engine timing to
the ECM.
f. The ECM signals the electronic throttle control
(ETC) to open, allowing fuel to flow into the
engine, and also controls the ignition module
through leads 116 and 117, providing spark for
combustion.
g. The ECM monitors feedback from the ETC
through leads TPS1 and TPS2 and adjusts the
ETC through leads ETN and ETP to achieve
the programmed engine speed.
h. The O2 (HEGO) sensor heater circuit is
activated at this time.
5. When the RDC2 controller detects engine crank
through CAN communication, the controller
initiates alternator excitation by sending low DC
voltage (1.2 VDC) through leads 3B and 5B.
Section 5 Troubleshooting 61