B1792

Code

Other B — Body

Autolamp Sensor Input Circuit Short To Battery

Brand: Other

Type: B — Body

Views: UK: 24 EN: 27 RU: 20

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Page language: EN

Causes

Shorted wiring to battery voltage (pin-to-battery positive)
Faulty/failed autolamp (ambient light) sensor with internal short
Corroded/damaged connector or pin contact applying battery voltage to the sensor circuit
Aftermarket accessories tied into lighting or constant-power circuits
Damaged insulation allowing contact with a fused battery feed
Control module (BCM/BCU) internal fault or damaged sensor driver circuit

Symptoms

DTC B1792 stored in body/control module memory
Automatic headlamp function disabled or inoperative
Headlamps may remain on or behave erratically
Possible battery drain if the circuit backfeeds when vehicle off
Related illumination/warning messages on dash in some vehicles

What to check

Read and record freeze-frame and related codes with a scan tool; note conditions when code set
Visually inspect sensor, harness, and connector for damage, corrosion, or water entry
Back-probe sensor connector with ignition ON and measure voltage on the signal pin
With sensor disconnected, check if the signal circuit still reads battery voltage (indicates short in harness or accessory)
Wiggle harness and observe live data or scan tool for intermittent changes
Inspect for aftermarket lamps, alarms, or wiring taps near the sensor harness

Signal parameters

Nominal autolamp sensor output: typically 0–5 V (vehicle-dependent)
Valid operating range: sensor output normally < battery voltage (should NOT equal battery voltage)
Short-to-battery condition: ~vehicle battery voltage (≈11–15 V) measured at signal pin
Short-to-ground condition: ~0 V at signal pin
Typical sensor circuit current: very low (milliamps); significant current suggests short/shorted element

Diagnostic algorithm

Retrieve all stored codes and freeze-frame data. Confirm B1792 is current and note operating conditions when set.
Perform a visual inspection of the autolamp sensor, its mounting, and the full harness to the body control module. Look for chafing, pinched sections, corrosion, or signs of water intrusion.
With ignition ON (engine off OK), back-probe the sensor harness connector and measure voltage at the signal pin. Compare to expected (typically 0–5 V). If signal measures battery voltage, proceed to step 4.
Disconnect the sensor. With sensor disconnected and ignition ON, measure the voltage on the wiring harness signal conductor. If it still reads battery voltage, the short is in the harness, connectors, or an aftermarket tap. Trace harness and remove/follow any accessory taps.
If harness signal reads low after disconnecting or open, test the sensor on bench or replace with known-good sensor and re-test. If replacement clears code, repair was the sensor.
Use a low-current tracer or ohmmeter (power off) to check continuity between the signal wire and battery positive to locate short. Repair any chafed wires, replace damaged connectors, and resleeve wiring as required.
After repairs, clear codes and perform functional test of autolamp operation over several ignition cycles. If wiring and sensor check OK but DTC returns, suspect control module fault and consider module bench test/repair or replacement as last resort.
Safety note: isolate circuits and follow vehicle manufacturer precautions when probing live circuits; use fused jumpers and avoid creating new shorts.

Likely causes

Wiring short between sensor signal wire and a nearby fused 12V feed
Water ingress corrosion at sensor or connector causing internal short
Faulty autolamp sensor element internally shorted to its supply
Connector pins bent or pushed to touch 12V source or terminal

Fault status

⚠️ Status

Autolamp Sensor Input Circuit Short To Battery – control module detected the sensor input voltage is being held at battery potential. Automatic lamp control may be disabled until circuit fault is corrected.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours