B1802: How to Diagnose & Fix — Lamp Turn Signal Rear Output Circuit (manufacturer-specific)
2 vehicles · 2 makes · $90-$900 repair
How to diagnose and fix B1802: most-reported vehicles
Ranked by owner reports. Each card gives the symptoms, how to confirm the cause, the fix, parts and sources for that vehicle.
Jeep Compass · 2007–2020
The plastic gears inside the temperature blend door actuator strip, so the actuator motor free-spins and ratchets. Owners hear a rapid tick-tick-tick from behind the glovebox or center dash for several seconds after startup and every time the temperature or mode is changed, and one side of the cabin (or the whole system) gets stuck blowing only hot or only cold. The failure is common on the MK Compass and carries into the MP; the recirculation and mode actuators use the same gear train and fail the same way. It is a wear item rather than a control-head fault, so replacing the climate control head does not fix it.
Common Symptoms
- Rapid clicking or ticking from behind the glovebox or dash
- Clicking for a few seconds after starting or shutting off the car
- Temperature stuck on hot or cold regardless of setting
- Air comes out of the wrong vents / mode will not change
- Driver and passenger sides at different temperatures on dual-zone
How to Fix
Identify which actuator is ratcheting by sweeping temperature cold-to-hot and toggling recirculation while listening. Drop the glovebox (and on some cars the lower dash panel) to reach the actuator, unplug it, remove the two or three screws and swap in a new unit - Mopar OEM is strongly preferred because aftermarket units often mis-calibrate. After installation, cycle the ignition and let the HVAC module run its automatic actuator calibration, or run the calibration routine with a scan tool.
Sources for this issue (2)
Toyota Corolla · 2009–2013
A common problem on 10th-generation Corolla models is failure of the steering wheel spiral cable, also called the clock spring. When the ribbon circuit inside the cable breaks, the SRS warning light illuminates and steering-wheel-mounted functions such as the horn or audio switches may stop working. Toyota issued a warranty enhancement and many owners also documented the issue through NHTSA complaints and forum reports.
Common Symptoms
- airbag warning light on
- horn inoperative
- steering wheel audio/cruise buttons stop working
- intermittent SRS light
- airbag system fault stored
How to Fix
Diagnosis usually starts by scanning the airbag system for driver-side squib or spiral cable communication faults, then checking whether the horn and steering wheel buttons also fail intermittently. Repair is replacement of the spiral cable assembly and clearing SRS codes; care is required because the airbag module must be removed and the replacement part must be centered correctly before installation.
Sources for this issue (1)
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B1802 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does B1802 mean?
B1802 stands for "Lamp Turn Signal Rear Output Circuit (manufacturer-specific)." B1802 is a manufacturer-specific body code, associated mainly with Ford-family lighting systems, that generally indicates a fault in the rear turn-signal lamp output circuit detected by the lighting/body control module. Because it is manufacturer-specific, the precise wording and fault type (open, short, or failure) can vary by make and model and should be confirmed against the vehicle's service information. The practical effect is typically an inoperative or improperly functioning rear turn signal.
What are the most common causes of B1802?
The most common causes of B1802 are: Fault (short or open) in the rear turn-signal wiring, Faulty rear turn-signal bulb, Corroded or damaged bulb socket/connector, Chafed or pinched rear harness, Water intrusion in the rear lamp assembly, Internal fault in the lighting/body control module. The specific cause varies by vehicle.
How much does it cost to fix B1802?
Repair costs for B1802 range from $90 to $900, depending on the vehicle and root cause.
Which vehicles are affected by B1802?
Au7o has documented B1802 across 2 vehicle models from 2 manufacturers: Jeep, Toyota.
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.