COLLAR-SEAL 4897621 - Caterpillar

Diagnostics
Measure the value of the resistance in the recirculation sensor. See "Specifications". Proceed to step 2.
If the resistance value is incorrect see step 3. If the resistance value is correct see step 4.
Replace the recirculation sensor.
Disconnect the connectors from the sensor and measure the voltage between the connectors L GN/YL and GY/YL. See "Specifications". Proceed to step 5.
If the voltage value is incorrect see step 6. If the voltage value is correct see step 7.
Check the harness and repair the harness between the connector and the control unit. Also, check the system power source.
Fit the sensor and measure the voltage between terminals 12 and 27 of control unit. See "Specifications". Proceed to step 8.
If the voltage values are incorrect see step 9. If the voltage values are correct see step 10.
Check the harness and repair the harness between the connector and the control unit.
Replace the control unit.Specifications
Resistance in the recirculation sensor 0 °C (32 °F) ... 1.645 kOhms 25 °C (77 °F) ... 5 kOhmsVoltage between connectors ... 5.0 VVoltage between terminals 10 °C (50 °F) ... 3.43 V 20 °C (68 °F) ... 2.87 V 25 °C (77 °F) ... 2.59 V 30 °C (86. °F) ... 2.32 V