62-12259 7–52
00121 Check Ambient Air Sensor
• ACTIVATION: Ambient Air Temperature Sensor (AAT) is not within range of -53 to +158°F (-47° to +70° C).
• UNIT CONTROL: Engine and Electric Operation: A value of 122°F (50°C) will be used for any calculations.
• RESET CONDITION: Auto reset when sensor is in range or alarm may be manually reset using the
display mounted keys 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 (refer to reset condition above). Operate the unit through the appro-
priate modes to see if any active alarm occurs. Continue with the steps below as necessary.
Corrective Actions:
1. Check Sensor
a. Inspect sensor and connector. No damage to sensor. No damage, moisture, or corrosion in
connector.
b. Check sensor resistance. (Refer to Note 3 in Notes Section) 10,000 Ohms @ 77°F (25°C). Refer to
Table 8–5 for chart of resistances for different sensors.
2. Check Sensor Wiring
a. Inspect connector pins and terminals at sensor and connector
1-3MSM-1 and 24
. (See wiring
schematic Section 10.2.) Verify there is no physical damage to harness, and no damage, moisture,
or corrosion in connectors.
b. Place the system in PC Mode. Refer to Note 2 in Notes Section Disconnect sensor from harness.
Check for 3.0 ± 0.1 VDC at harness plug between pins. Voltage should be 3.0 ± 0.1 VDC volts at
harness plug between pins. This verifies microprocessor.
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