Kohler Command CH25

5B.45
Section 5B
EFI Fuel System
5B
Diagnostic Aid #4 “SPEED SENSOR” (MIL does not
turn off during cranking). Indicates the ECU is not
receiving a signal from the speed sensor.
Possible causes:
1. Speed sensor
2. Speed sensor circuit problem
“35 Pin” (MA 1.7) Metal-Cased ECU: Pin circuits
3 and 21.
“24 Pin” (MSE 1.0) Plastic-Cased ECU: Pin
circuits 9 and 10.
“32 Pin” (MSE 1.1) Plastic-Cased ECU: Pin
circuits 9 and 10.
3. Speed sensor/toothed wheel air gap
4. Toothed wheel
5. Flywheel key sheared
6. ECU
Diagnostic Aid #5 “FUEL PUMP” (fuel pump not
turning on)
Possible causes:
1. Fuel pump fuse
2. Fuel pump circuit problem
“35 Pin” (MA 1.7) Metal-Cased ECU: Circuits 43,
44, and relay.
“24 Pin” (MSE 1.0) Plastic-Cased ECU: Circuits
30, 87, and relay.
“32 Pin” (MSE 1.1) Plastic-Cased ECU: Circuits
30, 87, and relay.
3. Fuel pump
Diagnostic Aid #6 “RELAY” (relay not operating)
Possible causes:
1. Safety switches/circuit(s) problem
“35 Pin” (MA 1.7) Metal-Cased ECU: Circuits 41
and 41A.
“24 Pin” (MSE 1.0) Plastic-Cased ECU: Circuit 3.
“32 Pin” (MSE 1.1) Plastic-Cased ECU: Circuit
25.
2. Relay circuit(s) problem
“35 Pin” (MA 1.7) Metal-Cased ECU: Circuits 28,
41, and 41A.
“24 Pin” (MSE 1.0) Plastic-Cased ECU: Circuits
18, 85, 30, and 87.
“32 Pin” (MSE 1.1) Plastic-Cased ECU: Circuits
28,85, 30, and 87.
3. Relay
4. ECU grounds
5. ECU
Diagnostic Aid #7 “IGNITION SYSTEM” (no spark)
Possible causes:
1. Spark plug
2. Plug wire
3. Coil
4. Coil circuit(s)
“35 Pin” (MA 1.7) Metal-Cased ECU: Circuits 1,
19, 40, 40A, 43, and relay.
“24 Pin” (MSE 1.0) Plastic-Cased ECU: Circuits
22, 23, 65, 66, 30, and relay.
“32 Pin” (MSE 1.1) Plastic-Cased ECU: Circuits
30, 31, 65, 66, relay and relay circuit 30.
5. ECU grounds
6. ECU
Diagnostic Aid #8 “FUEL SYSTEM-ELECTRICAL”
(no fuel delivery)
Possible causes:
1. No fuel
2. Air in fuel rail
3. Fuel valve shut off
4. Fuel filter/line plugged
5. Injector circuit(s)
“35 Pin” (MA 1.7) Metal-Cased ECU: Circuits 35,
35A, 45, and 45A.
“24 Pin” (MSE 1.0) Plastic-Cased ECU: Circuits
16, 17, 45, and 45A.
“32 Pin” (MSE 1.1) Plastic-Cased ECU: Circuits
14,15, and 45.
6. Injector
7. ECU grounds
8. ECU
Diagnostic Aid #9 “FUEL SYSTEM” (fuel pressure)
Possible causes for low fuel system pressure:
1. Low fuel
2. Fuel filter plugged
3. Fuel supply line plugged
4. Pressure regulator
5. Fuel pump
Possible causes for high fuel system pressure:
1. Pressure regulator
2. Fuel return line plugged or restricted.
Diagnostic Aid #10 “BASIC ENGINE” (cranks but
will not run)
Possible causes:
1. Refer to basic engine troubleshooting charts
within service manual sections 3, 5, and 8.