Code
B1773
MERCEDES-BENZ
B — Body
HRA: Zero position programming has not yet been carried out or is not possible
Views:
UK: 11
EN: 12
RU: 12
AI status
Completed
Completed
100%
Causes
- Zero-position/teach-in procedure not performed after service or battery disconnect
- Faulty or failed headlamp range actuator (motor/encoder/potentiometer)
- Mechanical binding or obstruction in the headlamp leveling mechanism
- Poor power supply or ground to the actuator (low battery voltage, corroded connector)
- Damaged wiring or connector between actuator and body control module
- Control module software or calibration lost or corrupted
Symptoms
- Dash message or service lamp related to headlamp leveling/adaptive headlights
- Automatic headlight leveling not functioning or not adjusting
- Headlamp aim incorrect or asymmetric beam height
- Stored DTC B1773 in body or lighting control module
- Attempting basic settings/teach-in fails or times out
What to check
- Read fault memory with a Mercedes-capable scan tool and record freeze frame data
- Check battery voltage (should be within manufacturer specification) and ensure stable power during programming
- Inspect headlamp leveling actuator connectors for corrosion, bent pins, water ingress and secure fit
- Visually and manually check headlamp leveling linkage and actuator for free movement and absence of obstructions
- Attempt to perform zero-position/teach-in procedure with OEM diagnostic tool and note error or failure point
- Check for related codes (power/communications) in lighting and body control modules
Signal parameters
- Actuator supply voltage (V)
- Actuator ground continuity
- Actuator commanded position (degrees or counts) from control module
- Actuator actual position/encoder counts/feedback value
- Status/learning flag for HRA (learned/not learned)
- CAN or LIN messages between body module and headlamp control
Diagnostic algorithm
- Read and record all DTCs and freeze frame data from the body/lighting control modules with an OEM-level scan tool.
- Verify battery state of charge and charging system; connect stable power or a battery charger if voltage is low. Retest programming with full voltage.
- Visually inspect headlamp leveling actuator, wiring harness and connector for damage, corrosion, water ingress and secure pins. Repair any wiring/connector issues.
- Manually move the headlamp leveling linkage (with ignition off) to check for mechanical binding or foreign objects. Correct any mechanical obstruction.
- With scan tool, attempt zero-position/initialization (basic settings/teach-in) for HRA following the manufacturer procedure. Watch live data for actuator commanded vs. feedback values and for error messages/timeouts.
- If programming fails, measure supply voltage and ground at the actuator connector during a programming attempt. Measure resistance of actuator motor and position sensor per service manual specs.
- If actuator receives correct voltage/commands but feedback does not change or is out of range, replace the headlamp range actuator (or its position sensor) and repeat the zero-position programming.
- If actuator replacement does not resolve the issue, check the lighting/body control module for software updates, calibration or replacement and verify vehicle bus communications (CAN/LIN).
- After repair and successful learn/teach-in, clear codes and verify operation by cycling lighting and performing test drive/validation. Re-scan to confirm no recurring faults.
Likely causes
- Actuator not programmed after replacement or battery replacement
- Defective actuator position sensor (encoder/potentiometer)
- Connector corrosion or loose pin at actuator
- Mechanical seized linkage or foreign object preventing travel
Fault status
Status
Headlamp range actuator zero position not programmed or programming impossible. HRA needs initialization or repair (electrical, mechanical or control-side).
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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