62-11640 7–6
00012 HIGH COOLANT TEMPERATURE - CONTINUED
5. Check Engine Coolant Temperature Sensor (ENCT)
a. Refer to procedure for alarm 00129 CHECK ENG COOLANT SENSOR. Alarm condition must be
corrected and the alarm cleared to continue.
b. Inspect sensor & connector pins & terminals. Verify no damage to sensor. Verify no damage, mois-
ture, or corrosion in connector.
c. Check sensor resistance. (Refer to Note 3 in Notes Section, page 7-2.) 10,000 Ohms @ 77°F
(25°C.) Refer to Table 8–4 for complete table of temperatures & resistance values.
6. Check Engine Coolant Temperature Sensor Wiring
a. Inspect harness & control box connector pins & terminals. (See wiring schematic Section 10.3).
Verify no physical damage to harness and no damage or corrosion in connectors.
b. Check voltage at the sensor connector with the microprocessor powered up. Voltage reading
should be 2.5 ± 0.1 VDC. This verifies microprocessor output and wiring connections to sensor.
7. Check Engine Cooling System
a. Compare actual engine temperature to the Unit Data reading. Refer to Section 3.14. Temperature
must be within ± 20°F (± 11.1°C).
b. Test operation of thermostat. Must operate correctly.
c. Check water pump operation. Verify no seepage at weep hole, bearings tight and quiet, and Impel-
ler firmly attached to shaft.
d. Check cooling system for scale, sludge, rust, etc. Coolant must be clean & clear with no foreign
particles or substances in it. Flush & clean the coolant system as necessary.
e. Check water pump bypass hose to thermostat housing for internal blockage. Must be clear and
open.
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