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Tahoe / Yukon Service Manual

Rain Sensor Malfunction

Diagnostic Instructions Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Review Strategy Based Diagnosis for an overview of the diagnostic approach. Diagnostic Procedure Instructions provides an overview of each diagnostic category. Diagnostic Fault Information

Circuit Number Circuit Descriptio Short to n Ground Open/High Resistance Short to Voltage Signal Performan
4540 B+ U0231 U0231 — —
4116 Serial Data U150E U150E U150E —
2351 Ground — U0231 — —

Circuit/System Description The B117A Windshield Outside Moisture/Ambient Light and Humidity Sensor utilizes an internal infrared LED and an optic sensor to determine the amount of water on the windshield. The infrared LED bounces infrared light against the inside of the windshield. The optic sensor measures the amount of light returned after bouncing off the windshield. With a dry windshield, all light bounced off the windshield is returned to the optic sensor. As water accumulates on the windshield, the light input to the optic sensor is diffused and reduced. The amount of light reduction corresponds directly to the amount of water on the windshield. The B117A Windshield Outside Moisture/Ambient Light and Humidity Sensor interprets the amount of light returned and communicates this info to the K9 Body Control Module, which will control intermittent wiper operation based on the sensitivity selection of the S82 Windshield Wiper/Washer Switch and the amount of water on the windshield. Diagnostic Aids Dirt/debris on windshield can cause B117A Windshield Outside Moisture/Ambient Light and Humidity Sensor to not work properly. Sensor needs to be properly seated against windshield. Air gap can cause improper operation. Due to the sensitivity of the sensor, the wipers may swipe once upon start up or rapid lighting changes. This is normal operation and does not need any further diagnosis. Reference Information Schematic Reference Wiper/Washer Schematics Connector End View Reference Master Electrical Component List Description and Operation Wiper/Washer System Description and Operation Electrical Information Reference Circuit Testing Connector Repairs Testing for Intermittent Conditions and Poor Connections Wiring Repairs Scan Tool Reference Control Module References for scan tool information Circuit/System Verification

  1. Ignition ON.
  2. Verify there are no communication DTCs set. ⇒ If DTCs are set Refer to: Diagnostic Trouble Code (DTC) List - Vehicle
  3. Verify the sensor is properly seated against windshield and there are no air gaps. ⇒ If air gap is present Remove and reinstall sensor ⇓ If no air gap is present
  4. Place the S82 Windshield Wiper and Washer Switch in the intermittent delay setting and spray the outside of the windshield in the area of the B117A Windshield Outside Moisture/Ambient Light and Humidity Sensor with water . It may be necessary to increase the sensitivity of the intermittent delay to achieve windshield wiper operation.
  5. Verify the windshield wipers operate at low speed. ⇒ If the wipers are not operating at low speed Refer to Circuit/System Testing. ⇓ If the wipers are operating at low speed
  6. A fault is not currently present and may be an intermittent condition. Circuit/System Testing
  7. Ignition OFF, all vehicle systems OFF, disconnect the connector at the B117A Windshield Outside Moisture/Ambient Light and Humidity Sensor. It may take up to 2 min for all vehicle systems to power down.
  8. Test for less than 10 Ω between the ground circuit terminal 3 and ground. ⇒ If 10 Ω or greater Repair the open/high resistance in circuit 2351 or ground connection. ⇓ If less than 10 Ω
  9. Ignition ON, verify a test lamp illuminates between the B+ circuit terminal 1 and ground. ⇒ If the test lamp does not illuminate and the circuit fuse is good 3.1. Test circuit 4540 for an open/high resistance. ⇒ If an open/high resistance is found, repair the fault on the circuit. ⇓ If an open/high resistance is not found. 3.2. Refer to: Retained Accessory Power Malfunction ⇒ If the test lamp does not illuminate and the circuit fuse is open 3.1. Test circuit 4540 for a short to ground. ⇒ If a short to ground is found, repair the fault on the circuit. ⇓ If a short to ground is not found. 3.2. Replace the B117A Windshield Outside Moisture/Ambient Light and Humidity Sensor. ⇓ If the test lamp illuminates
  10. Ignition OFF, remove the test lamp, ignition ON.
  11. Test for 5–10 V between the serial data circuit terminal 2 and ground. ⇒ If not 5–10 V Refer to: DTC U1500-U15FF ⇓ If between 5.0–10.0 V
  12. Replace the B117A Windshield Outside Moisture/Ambient Light and Humidity Sensor. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair. Windshield Outside Moisture/Ambient Light and Humidity Sensor Replacement Control Module References