62-11389
7−71
Alarm
NO.
Steps Alarm/Cause Corrective Action
129 CHECK ENG COOLANT SENSOR
• TRIGGER–ON: Engine Coolant Temperature Sensor (ENCT) is not within the range of -58 to
+266°F (-50 to +130°C).
• UNIT CONTROL: Engine Operation: Alarm Only.
Standby Operation: This alarm does not activate in standby.
• RESET CONDITION: Auto Reset or alarm may be manually reset via keypad or by turning the unit
off, then back on again.
NOTE: Follow the steps below until a problem is found. Once a repair or correction has been made, the active
alarm should clear itself (see reset condition above). Operate the unit through the appropriate modes to see if
any active alarm occurs. Continue with the steps below as necessary.
1 Check Sensor
a. Inspect sensor & connector. No damage to sensor.
No damage, moisture, or corrosion in connector.
b. Check sensor resistance. (See
Note 3, page 7−2.)
10,000 Ohms @ 77°F (25°C.) See Table 8−5 for
complete table of temperatures and resistance
values.
2 Check Sensor Wiring
a. Inspect harness & control box
connector pins & terminals. (1MP,
see wiring schematic Section 10).
No physical damage to harness.
No damage, moisture, or corrosion in connectors.
b. Power up the microprocessor (see
Note 2 page 7−2). Disconnect
sensor from harness. Check for
2.5 VDC at harness plug between
pins.
Voltage should be 2.5 VDC volts at harness plug be-
tween pins. This verifies microprocessor output and
wiring connections to sensor.
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