B1810

Code

Other B — Body

Lamp Backup Switch Input Circuit Failure

Brand: Other

Type: B — Body

Views: UK: 30 EN: 42 RU: 29

AI status

Completed

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Page language: EN

Causes

Open or short in wiring between reverse lamp switch and BCM
Corroded/damaged connector at switch or BCM
Failed reverse lamp switch (mechanical or electrical)
Blown fuse or poor ground for backup lamps circuit
Burned or shorted backup lamp bulb(s)
Intermittent BCM input or BCM internal fault

Symptoms

Backup (reverse) lamps do not illuminate when transmission in reverse
Backup lamps remain on continuously
Reverse lights flicker or are intermittent
Associated systems (rear camera, parking sensors, shift interlock) may not operate or show faults
DTC B1810 stored and possibly related BCM warnings

What to check

Read freeze frame and live data with a scan tool; check when fault sets and whether reverse input changes when gear selected
Visually inspect bulbs, lamp sockets, fuses, and ground connections for damage or corrosion
Inspect wiring and connectors at the backup lamp switch, BCM, and rear lamp assemblies
Check for continuity between the switch and BCM connector; check for shorts to battery or ground
Backprobe switch and BCM input with transmission in park and in reverse to confirm expected voltage or continuity
Wiggle-test harness while monitoring signal to reproduce intermittent fault

Signal parameters

Switch rest: open (no continuity) or 0 V at BCM input (depending on vehicle design)
Switch active (reverse engaged): closed to 12 V or continuity to ground depending on circuit; expect battery voltage ~12–14 V or near 0 V if switch grounds the circuit
Voltage should switch cleanly between states when selecting reverse; no slow rise/fall or noise
Expected continuity when closed: near 0 ohms; expected open-circuit when open
Lamp circuit current when active: typically small for switch input (mA); lamp current higher at lamp sockets (100s of mA)

Diagnostic algorithm

Connect a scan tool, confirm B1810 present, note freeze-frame/live data and whether code is current or historic.
Verify the symptom: place transmission in reverse and observe reverse lamps and scan tool input status.
Inspect fuse(s) for the tail/backup lamp circuit; replace if blown and retest.
Visually inspect rear lamp bulbs and sockets; replace any burned or corroded bulbs and retest.
Inspect connectors at reverse switch and BCM for corrosion, bent pins, or loose terminals; repair as needed.
Backprobe the switch wiring at the switch and at the BCM while selecting reverse: verify expected voltage or continuity change. Record values.
If signal does not change at switch, replace or bench-test the reverse lamp switch; if signal correct at switch but not at BCM, check continuity of wiring harness between switch and BCM.
Check for shorts: with a multimeter, measure resistance to battery positive and to ground to find unintended shorts or opens.
If wiring and switch are good but input intermittent at BCM, inspect BCM connector and perform wiggle test; if internal BCM input failure suspected, confirm with manufacturer procedures before replacement.
Clear codes and retest by cycling ignition and placing vehicle in reverse several times to confirm repair; monitor for reoccurrence.

Likely causes

Damaged harness or connector at the transmission shifter/reverse switch
Switch stuck or internal contact failure
Corroded pins causing intermittent connection
Pinched wire shorting to power or ground
Blown fuse protecting the lamps or switch circuit

Fault status

⚠️ Status

Backup lamp switch input circuit failure detected by BCM. Signal missing, shorted, or out of range; BCM stored B1810. May cause reverse lights or related systems to fail.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours