Actron CP9087 Service Manual

Contents

Actron CP9087 Service Manual Manual pdf 10 page image

Section 22-2Engine TEMPERATUREWhat toInspectSensor operation (see test on page 2-4). Poorconnections at sensor or computer. Faulty sensorwiring (open or short circuits). Heavy deposits onsensor tip which can cause poor response.Leakage into sensor housing. Engine running toohot (problems with antifreeze, thermostat, waterpump, fan, belts, low engine oil).When to Test • Related trouble codes sent by computer.• Driveability problems such as hard starting,rough idle, stalling, hesitation, stumble, surging,knocking (pinging), poor fuel economy, or blackexhaust smoke.Location The sensor is usually threaded into the engineblock, lower intake manifold, or cylinder head toprovide direct contact with coolant.How is ItUsed?The computer needs to know engine temperatureso it can modify air/fuel ratios, spark advance, idlespeed, and emission device operation (such as anEGR valve).What is It? The engine temperature sensor is a thermistor - aresister whose resistance changes with tempera-ture. The hotter the sensor gets, the lower theresistance becomes. The thermistor is mountedinside the tip of a threaded metal housing. This is a2-wire sensor. (Exception: some Chrysler engineshave a dual sensor with three wires.)HIGHSENSORRESISTANCELOWCold HotTEMPERATURETypical Engine CoolantTemperature Sensor