RAIN-SENSING WIPER SYSTEM – AUTOMATED WINDSHIELD VISIBILITY LOGIC
System Overview
The Rain-Sensing Wiper System on the 2011 Grand Cherokee Overland Summit utilizes an optical moisture sensor mounted behind the rearview mirror to detect the presence and intensity of water droplets on the windshield. This sensor communicates with the Body Control Module (BCM) to initiate wiper movement based on configurable sensitivity settings. The system engages automatically when the wiper stalk is placed in the auto position.
- Sensor Type: Optical infrared sensor bonded to inner windshield surface
- Module Interface: Integrated with BCM and steering column controls
- Operating Conditions: Ignition ON, stalk in AUTO, sensor calibrated and unobstructed
- Auto Wipe Speed: Variable delay/intermittent to full-speed sweep
Functional Logic
The sensor emits infrared light into the windshield glass and monitors reflection behavior. When moisture disrupts the refractive index, it signals the BCM to activate the wipers. Sensitivity can be adjusted using the ring on the wiper stalk, ranging from low to high reactivity. The system adjusts sweep rate dynamically depending on moisture accumulation, road speed, and prior engagement profile.
- Sensitivity Adjustment: Stalk ring with low-mid-high delay modulation
- Speed Scaling: Higher road speed reduces delay interval between sweeps
- Clearing Behavior: Final sweep after spray wash or upon rain stop detection
- Manual Override: Stalk movement to LO/HI cancels AUTO until reset
System Limitations
Rain-Sensing Wiper function can be impaired by windshield contamination (dirt, bugs, ice), sensor misalignment, or aftermarket tint films. It does not detect precipitation on the rear or side windows. False activation may occur from overhead sprinklers or mist. Manual wiper function is always available regardless of sensor state.
- Sensor Blockage: Dirt or residue over sensor lens reduces accuracy
- Tint Interference: Improper aftermarket film may distort sensor optics
- False Activation: Spray patterns from other vehicles or high fog density
- Rear Wiper: Not rain-sensing; activated by reverse gear or manual toggle
Service & Diagnostics
Diagnosis of the Rain-Sensing Wiper System is performed via BCM-connected scan tools. Fault codes may appear if the sensor loses connection or cannot communicate during key cycles. Replacement requires careful detachment of the optical lens housing and reinstallation onto a clean glass surface with bonding gel.
- Common DTCs: B101D (sensor communication lost), B1020 (bad signal quality)
- Sensor Replacement: Bonded sensor plate with harness clip removal
- Scan Tool Path: Body Control > Rain Sensor > Live Data + Calibration
- Calibration: Passive – completes automatically on clean, dry windshield at key cycle
Retrofit & Disable
The system cannot be retrofitted to non-equipped vehicles without BCM programming and windshield sensor mount. For off-road or winter builds, the rain-sensing function can be disabled via the infotainment menu or by disconnecting the sensor. Manual wiper operation remains fully functional and unaffected by sensor state.
- Disable Path: Settings > Vehicle > Wipers > Auto Rain-Sense Off
- Sensor Harness: Disconnect to eliminate system function (retains manual control)
- Replacement Glass: Must include sensor window if OEM replacement is required
- Compatibility Warning: Aftermarket windshields may cause misalignment