Kohler Aegis LH775 Service Manual page 40

EFI System
Code 42
Component: Engine (Oil) Temperature Sensor
Fault: Not sending proper signal to ECU.
Condition: Engine may be hard to start because
ECU can't determine correct fuel mixture.
Conclusion: Temperature Sensor Related
● Sensor wiring or connection.
Engine Wiring Harness Related
● Pin circuits 4, 6 and/or (4A) damaged
(wires, connectors) or routed near
noisy signal (coils, alternator, etc.).
● ECU-to-harness connection problem.
System Related
● Engine is operating above 176°C
(350°F) temperature sensor limit.
Code 43 and 44
Component: TPS Auto-Learn initialization function
failed, throttle angle out of learning range.
Fault: While performing TPS Auto-Learn
function, measured throttle angle was not
within acceptable limits.
Condition: MIL illuminated. Engine will continue to
run but not properly. Upon restart TPS
Auto-Learn function will run again unless
voltage to ECU disconnected to clear
memory.
Conclusion: TPS Related
● TPS rotated on throttle shaft assembly
beyond allowable range.
● TPS bad.
Engine Wiring Harness Related
● Broken or shorted wire in harness.
ECU pin 18 to TPS pin 1.
ECU pin 4 to TPS pin 2.
ECU pin 8 to TPS pin 3.
Throttle Body Related
● Throttle shaft inside TPS worn, broken,
or damaged.
● Throttle plate loose or misaligned.
● Throttle plate bent or damaged
allowing extra airfl ow past, or restricting
movement.
ECU Related
● Circuit providing voltage or ground to
TPS damaged.
● TPS signal input circuit damaged.
40
Code 51
Component: Injector #1 circuit open, shorted to
Fault:
Condition:
Conclusion: Injector Related
KohlerEngines.com
ground, or shorted to battery.
Injector #1 is not functioning because
circuit is open, shorted to ground, or
shorted to battery.
Engine will run very poorly with only one
cylinder functioning.
● Injector coil shorted or opened.
Engine Wiring Harness Related
● Broken or shorted wire in harness.
ECU pin 14 to injector pin 2. ECU
pin 28 to fuel pump relay pin 86.
Note: after key-off then key-on code
56 would be set also. Fuel pump
relay pin 87 to injector pin 1.
● Open main fuse F1.
Fuel Pump Relay Related
● Bad fuel pump relay. Primary side
functional but pin 30 to pin 87 remains
open. Primary side pin 85 to pin 86 is
either open, or shorted during engine
operation. Note: after key-off then
key-on code 56 would be set also.
ECU Related
● Circuit controlling injector #1 damaged.
● Circuit controlling fuel pump relay
damaged.
66 690 07 Rev. --