testing the air temp sesnor

rickb78 · Post by **rickb78** » 27 Jun 2011, 15:23

Good afternoon. It's really hot here in southeast Texas right now made more so by the air temp sensor in my 91 740 with the Regina ignition system. The OBD indicates code 1-2-2, which appears to be the air temp sensor on the air intake hose to the manifold. How do you check if the sensor is working?

Post by **billofdurham** » 28 Jun 2011, 12:25

Disconnect the sensor. To check the power supply switch on the ignition and connect a voltmeter between terminal 1 and earth (ground). The reading should be approximately 5 volts. Terminal 1 on the power side is the right hand terminal looking at the connector.

To check the resistance of the sensor connect an ohmmeter between the pins to read:
-20°C (4°F) 15,000 ohms
20°C (68°F) 2500 ohms
100°C (212°F) 160 ohms

Bill.

rickb78 · Post by **rickb78** » 29 Jun 2011, 19:17

Thank you Bill. Checking the resistance on the sensor it registers between 80-100 ohms with outside temp in the very high 90s. The battery is just about gone so couldn't measure the voltage. I'll see if I can jump it this weekend then check the voltage. Thank you very much for your help. When I get the voltage reading I'll respond.

rickb78 · Post by **rickb78** » 09 Jul 2011, 16:28

Have new battery on board now. The connector to the sensor reads 1.86 volts. No bueno as they say. I checked the ohms again. The ambient temp here is 98 in the shade: 80 ohms. So the problem is twofold, i.e. the sensor itself and not enough voltage coming thru the connector?