Check the resistance.

1. Using an ohmmeter, measure the resistance between the terminals.
   

   Standard resistance:

   Tester Connection	Specified Condition
   1 (HA1A) - 2 (+B)	1.8 to 3.4 Ω at 20°C (68°F)
   1 (HA1A) - 4 (A1A-)	10 kΩ or higher

   If the resistance is not as specified, replace the sensor.