8924 690 01 Rev. K KohlerEngines.com
EFI SYSTEM-BOSCH
Code 56 "32 Pin" (MSE 1.1) Plastic-Cased ECU only.
Component: Fuel pump relay circuit open, shorted to
ground, or shorted to battery.
Fault: Fuel pump, ignition coils, and fuel
injectors will not function because fuel
pump relay circuit is either open, shorted
to ground, or may be “on” continuously if
shorted to battery.
Condition: Engine will not run, or fuel pump will
continue to run when switch is off.
Conclusion: Fuel Pump Relay Related
● Bad fuel pump relay.
Primary side open or shorted.
Fuel Pump Related
● Fuel pump open or shorted internally.
Engine Wiring Harness Related
● Fuel pump fuse F1 open.
● Broken or shorted wire in harness.
ECU pin 28 to fuel pump relay pin
86.
Ignition switch to fuel pump relay
pin 85.
ECU Related
● Circuit controlling fuel pump relay
damaged.
Code 61
Component:
Fault:
Condition: Denotes end of fault codes. If signaled
fi rst, no other fault codes are present.
Conclusion:
Troubleshooting Flow Chart
Flow chart provides an alternative method of
troubleshooting EFI system. Chart will enable you to
review entire system in about 10-15 minutes. Using
chart, accompanying diagnostic aids (listed after chart),
and any signaled fault codes, you should be able to
quickly locate any problems within system.
Flow Chart Diagnostic Aids
Diagnostic Aid #1 "system power" (MIL does not
illuminate when key is turned ON).
NOTE: MIL in Metal-Cased ECU systems is an LED.
MIL in Plastic-Cased ECU systems must be a
1/4 watt incandescent lamp.
Possible causes:
● Battery
● Main system fuse
● MIL light bulb burned out
● MIL electrical circuit problem
“35 Pin” (MA 1.7) Metal-Cased ECU: Pin circuits
31 and 31A.
“24 Pin” (MSE 1.0) Plastic-Cased ECU: Pin circuits
19 and 84.
“32 Pin” (MSE 1.1) Plastic-Cased ECU: Pin circuits
29 and 84.
● Ignition switch
● Permanent ECU power circuit problem
“35 Pin” (MA 1.7) Metal-Cased ECU: Pin circuit 16.
“24 Pin” (MSE 1.0) Plastic-Cased ECU: Pin circuit
1.
“32 Pin” (MSE 1.1) Plastic-Cased ECU: Pin circuit
1.
● Switched ECU power circuit problem
“35 Pin” (MA 1.7) Metal-Cased ECU: Pin circuit 17.
“24 Pin” (MSE 1.0) Plastic-Cased ECU: Pin circuit
2.
“32 Pin” (MSE 1.1) Plastic-Cased ECU: Pin circuit
2.
● ECU grounds
● ECU
Diagnostic Aid #2 “FAULT CODES” (Refer to detailed
fault code listing before fl ow chart and servicing
information for respective components)
● Code 21-Engine Speed Synchronization
● Code 22-Throttle Position Sensor (TPS)
● Code 23-Engine Control Unit (ECU)
● Code 31-Oxygen Sensor
● Code 32-Oxygen Sensor
● Code 33-Fuel System (temporary adaptation factor)
● Code 34-Fuel System (permanent adaptation factor)
● Code 42-Engine (Oil) Temperature Sensor
● Code 43-TPS “Auto-Learn” Initialization Function
(Below Min. Limit), "32 Pin" (MSE 1.1) Plastic-Cased
ECU only.
● Code 44-TPS “Auto-Learn” Initialization Function
(Above Max. Limit), "32 Pin" (MSE 1.1) Plastic-
Cased ECU only.
● Code 51-Injector 1, "32 Pin" (MSE 1.1) Plastic-
Cased ECU only.
● Code 52-Injector 2, "32 Pin" (MSE 1.1) Plastic-
Cased ECU only.
● Code 55-MIL Light, "32 Pin" (MSE 1.1) Plastic-
Cased ECU only.
● Code 56-Pump Relay, "32 Pin" (MSE 1.1) Plastic-
Cased ECU only.
● Code 61-End of Fault/Blink Code Transmission.
Diagnostic Aid #3 “RUN/ON” (MIL remains “on” while
engine is running)*
Possible causes:
● Fault codes which turn on MIL when engine is running.
● Code 21-Engine Speed Synchronization
● Code 22-Throttle Position Sensor (TPS)
● Code 23-Engine Control Unit (ECU)
● Code 31-Oxygen Sensor (shorted)
● Code 34-Fuel System (permanent adaptation at limit)
● Code 42-Engine (Oil) Temperature Sensor
● Code 43-TPS “Auto-Learn” Initialization Function
(Below Min. Limit), "32 Pin" (MSE 1.1) Plastic-
Cased ECU only.
● Code 44-TPS “Auto-Learn” Initialization
● Function (Above Max. Limit) "32 Pin" (MSE 1.1)
Plastic-Cased ECU only.
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