Actron CP7677 Operating Instructions Manual

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Actron CP7677 Operating Instructions Manual Manual pdf 29 page image

291. If engine is HOT let it COOL downbefore proceeding.Make sure all engine and transmis-sion fluids are at outside air tem-perature before proceeding with thistest!2. Insert BLACK test lead into COMtest lead jack.3. Insert RED test lead intotest lead jack.4. Disconnect wiring harness fromsensor.5. If testing Intake Air TemperatureSensor - Remove it from vehicle.All other temperature sensors canremain on vehicle for testing.6. Connect RED test lead to eithersensor pin.7. Connect BLACK test lead to re-maining sensor pin.8. Turn multimeter rotary switch todesired OHM range.If the approximate resistance is un-known, start at the largest OHMrange and decrease to the appropri-ate range as required. (See Settingthe Range on page 6)RedBlackHair DryerTypicalIntake AirTemperatureSensor9. View and record reading on dis-play.10. Disconnect multimeter test leadsfrom sensor and reconnect sen-sor wiring.This step does not apply to intake airtemperature sensors. For intake airtemperature sensors, leave multim-eter test leads still connected to sen-sor.11. Heat up sensor.If testing Intake Air Temperature Sen-sor:• To heat up sensor dip sensor tipinto boiling water, or...• Heat tip with a lighter if sensor tip ismetal or a hair dryer if sensor tip isplastic.• View and record smallest readingon display as sensor is heated.• You may need to decrease therange to get a more accurate read-ing.For all other temperature sensors:• Start engine and let idle until upperradiator hose is warm.• Turn ignition key OFF.• Disconnect sensor wiring harnessand reconnect multimeter testleads.• View and record reading on dis-play.12. Test Results.Good Sensor:• Temperature sensors HOT resis-tance is at least 300Ω less than itsCOLD resistance.• The key point is that the COLD re-sistance decreases with increasingtemperature.Bad Sensor:• There is no change between thetemperature sensors HOT resis-tance from the COLD resistance.• The temperature sensor is an openor a short circuit.A temperature sensor is a thermistor ora resistor whose resistance changes withtemperature. The hotter the sensor gets,the lower the resistance becomes. Typi-cal thermistor applications are enginecoolant sensors, intake air temperaturesensors, transmission fluid temperaturesensors, and oil temperature sensors.Test Procedure (see Fig. 32):Fig. 32Temperature Type Sensors