Kohler LH630-775 Service Manual page 72

Section 5B
EFI Fuel System
Code: 43 and 44
Source: TPS "Auto-Learn" initialization
function failed, throttle angle out of
learning range.
Explanation: While performing the TPS "Auto-
Learn" function the measured
throttle angle was not within
acceptable limits.
Expected Engine
Response: 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.
Possible Causes:
1. TPS related
a. TPS rotated on throttle shaft assembly out of
allowable range.
b. TPS bad.
2. Engine wiring harness related
a. 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.
3. Throttle body related
a. Throttle shaft inside TPS worn, broken, or
damaged.
b. Throttle plate loose or misaligned.
c. Throttle plate bent or damaged allowing
extra airflow past or restricting movement.
4. ECU related
a. Circuit providing voltage or ground to TPS
damaged.
b. TPS signal input circuit damaged.
Code: 51
Source: Injector #1 circuit open, shorted to
ground, or shorted to battery.
Explanation: Injector #1 is not functioning
because the circuit is open, shorted
to ground, or shorted to battery.
Expected Engine
Response: Engine will run very poorly with
only one cylinder functioning.
Possible Causes:
1. Injector related
a. Injector coil shorted or opened.
5B.32
2. Engine wiring harness related
a. 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.
b. Open main fuse F1.
3. Fuel pump relay related
a. 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.
4. ECU related
a. Circuit controlling injector #1 damaged.
b. Circuit controlling fuel pump relay damaged.
Code: 52
Source: Injector #2 circuit open, shorted to
ground, or shorted to battery.
Explanation: Injector #2 is not functioning because
the circuit is open, shorted to ground,
or shorted to battery.
Expected Engine
Response: Engine will run very poorly with
only one cylinder functioning.
Possible Causes:
1. Injector related
a. Injector coil shorted or opened.
2. Engine wiring harness related
a. Broken or shorted wire in harness. ECU pin
15 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.
b. Opened main fuse F1.
3. Fuel pump relay related
a. Bad fuel pump relay. Primary side functional,
but pin 30 to pin 87 remains open. Primary
side pin 85 to pin 86 is open or shorted during
engine operation. Note: After key-off then
key- on code 56 would be set also.
4. ECU related
a. Circuit controlling injector #2 damaged.
b. Circuit controlling fuel pump relay damaged.