Engine Wiring Harness Related; Throttle Body Related; Ecu/Harness Related; Ignition System Related - Kohler CH18-745 Service Manual

Kohler Engine Parts Call K&T 606-678-9623 or 606-561-4983
Code: 21
Source: Engine Speed Sensor
Explanation: ECU receiving inconsistent tooth
count signals from speed sensor.
Expected Engine
Response: Possible misfire as ECU attempts to
resynchronize, during which time fuel
and spark calculations are not made.
Possible Causes:
1. Engine Speed Sensor Related
a. Sensor connector or wiring.
b. Sensor loose or incorrect air gap.
c. Flywheel key sheared.
2. Speed Sensor Ring Gear Related
a. Damaged teeth.
b. Varying gap (gear loose/out of alignment).

3. Engine Wiring Harness Related

"35 Pin" (MA 1.7) Metal-Cased ECU:
a. Pin circuits 3 and/or 21 wiring or connectors.
b. Shielding for pin circuits 3 and/or 21 damaged
or not properly grounded.
c. Poor or improper grounds in system (battery,
ECU, oxygen sensor, shielding, fuel pump,
ignition output).
d. Pin circuits 3 and/or 21 routed near noisy
electrical signals (coils, spark plug lead, plug
connector).
3. Engine Wiring Harness Related
"24 Pin" (MSE 1.0) Plastic-Cased ECU:
a. Pin circuits 9 and/or 10 wiring or connectors.
b. Shielding for pin circuits 9 and/or 10 damaged
or not properly grounded.
c. Poor or improper grounds in system (battery,
ECU oxygen sensor, shielding, fuel pump,
ignition output).
d. Pin circuits 9 and/or 10 routed near noisy
electrical signals (coils, spark plug lead, plug
connector).
3. Engine Wiring Harness Related
"32 Pin" (MSE 1.1) Plastic-Cased ECU:
a. Pin circuits 9 and/or 10 wiring or connectors.
b. Shielding for pin circuits 9 and/or 10 damaged
or not properly grounded.
c. Poor or improper grounds in system (battery,
ECU, oxygen sensor, shielding, fuel pump,
ignition output).
d. Pin circuits 9 and/or 10 routed near noisy
electrical signals (coils, spark plug lead, plug
connector).

4. ECU/Harness Related

5. Ignition System Related

Code:
Source:
Explanation:
Expected Engine
Response:
Possible Causes:
1. TPS Sensor Related

2. Throttle Body Related

3. Engine Wiring Harness Related
3. Engine Wiring Harness Related
www.mymowerparts.com
EFI Fuel System
a. ECU-to-harness connection problem.
a. Non-resistor spark plug(s) used.
22
Throttle Position Sensor (TPS)
Unrecognizable signal is being sent
from sensor (too high, too low,
inconsistent).
A "limp-home" operating mode occurs,
with an overall decrease in operating
performance and efficiency. Fuel
delivery is based upon the oxygen
sensor and five mapped values only.
Rich running (black smoke) will occur
until "closed loop" operation is
initiated. A stumble or misfire on hard
acceleration and/or erratic operation
may be exhibited.
a. Sensor connector or wiring.
b. Sensor output affected or disrupted by dirt,
grease, oil, wear, or breather tube position
(must be to side opposite the TPS).
c. Sensor loose on throttle body manifold.
a. Throttle shaft or bearings worn/damaged.
"35 Pin" (MA 1.7) Metal-Cased ECU:
a. Pin circuits 12, 25 and/or 27 damaged (wiring
or connectors).
b. Pin circuits 12, 25 and/or 27 routed near noisy
electrical signal (coils, alternator).
c. Intermittent 5 volt source from ECU (pin circuit
25).
"24 Pin" (MSE 1.0) Plastic-Cased ECU:
a. Pin circuits 4, 8, and/or 14 damaged (wiring,
connectors).
b. Pin circuits 4, 8, and/or 14 routed near noisy
electrical signal (coils, alternator).
c. Intermittent 5 volt source from ECU (pin circuit
14).
Section 5B
5B
5B.37