FUEL INJECTION
90-883728 JULY 2001 Page 3B-31
Air Temperature Sensor and Head Temperature Sensor Test
Purpose: This test eliminates possibilities of improper fuel delivery related to air/head temperature sensors.
NOTE: Air/Head Temperature Sensor functioning can be monitored using the Digital Diag-
nostic Terminal (DDT). The Air Temperature sensor should indicate ambient air tempera-
ture. The Head Temperature sensor should indicate cylinder head water temperature. The
ECM will revert to a default temperature of 32
°
F (0
°
C) if it should lose either air or head
temperature sensor signal. The sensors can also be tested using a DMT2000 Digital Multi-
meter 91-854009A1.
58898
a
b
b
58893
a-Air Temperature Sensor b-Head Temperature Sensor
Disconnect temperature sensor harness and check continuity with digital or analog ohm-
meter test leads between both connector pins. With engine at temperature (F°) indicated,
ohm readings should be as indicated ±10%. There should be no continuity between each
connector pin and ground.
1. Disconnect and remove temperature sensors from engine.
2. Connect DMT (91-854009A1) to leads of sensor.
3. Place sensor in ice water while monitoring meter reading. Use chart (below) for refer-
ence.
Results: Resistance does not change inversely with temperature change. Replace defective temperature
sensor. Resistance changes inversely with temperature change. Temperature sensor OK.
Temperature Sensor Specifications
Fahrenheit Centigrade OHMS
257 125 340
248 120 390
239 115 450
230 110 517
221 105 592
212 100 680
203 95 787
194 90 915
185 85 1070
176 80 1255
167 75 1480
158 70 1752
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