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DTC codes / B03xx · Airbags, seats, doors, lights and comfort systems / B0337

B0337Passenger Seat Heater Circuit

B0337 indicates that the body control module (BCM) has detected a fault in the passenger seat heater circuit, which typically means the circuit is open, shorted to ground, or shorted to voltage. The BCM monitors the heater element and wiring for expected resistance and voltage, and when the readings fall outside the programmed range, it stores this code and may disable the heater function.

SystemBody
Code typeGeneric (all makes)
SeverityLow
Fix difficultyIntermediate
AreaAirbags, seats, doors, lights and comfort systems

Symptoms you may notice

  • The passenger seat heater fails to warm up when activated.
  • The seat heater indicator light may flash or stay off when the button is pressed.
  • Often no symptoms besides the warning light, especially if the heater is rarely used.
  • In some vehicles, the driver's seat heater may also be disabled as a fail-safe.
  • Intermittent operation of the passenger seat heater, working only on certain settings or after jiggling the connector.

Common causes, most likely first

  1. Failed passenger seat heater element (open circuit or shorted turns).
  2. Damaged or disconnected wiring harness under the seat, often from seat movement or cargo.
  3. Corroded or loose electrical connector at the seat heater or BCM.
  4. Faulty seat heater control module or relay, if equipped separately.
  5. Internal BCM fault causing incorrect monitoring of the heater circuit.
  6. Blown fuse or fusible link supplying power to the seat heater circuit.
  7. Aftermarket seat covers or accessories interfering with the heater element.

How to diagnose and fix it

  1. Verify the code with a scan tool and check for any related body codes before clearing.
  2. Inspect the seat heater fuse and replace if blown, then recheck the circuit.
  3. Visually inspect the wiring harness and connectors under the passenger seat for damage, corrosion, or loose pins.
  4. Measure resistance of the seat heater element with a multimeter and compare to specification.
  5. Check for voltage and ground signals at the heater connector when the switch is activated.
  6. If the element and wiring are good, test the seat heater control module or relay and replace if faulty.
  7. Clear the code and verify the heater operates correctly through all settings.

Before you replace the seat heater element

  • A common misdiagnosis is replacing the seat heater element when the real problem is a pinched wire under the seat from normal seat adjustment.
  • The BCM may set B0337 if the seat heater is left on with the engine off, causing a low-voltage condition that trips the circuit monitor.
  • Aftermarket seat covers or heavy objects on the passenger seat can damage the heater element and trigger this code without any visible exterior damage.
  • On some vehicles, the passenger seat heater circuit shares a ground with other seat functions, so a bad ground can cause multiple codes including B0337.
  • The code can be stored intermittently if the connector under the seat is loose but makes contact most of the time, so always wiggle-test the harness while monitoring live data.

Can I keep driving with B0337?

The vehicle is safe to drive because the passenger seat heater is a comfort feature and does not affect engine or safety systems. Avoid using the passenger seat heater until the fault is repaired to prevent further damage or a potential fire risk from a shorted circuit.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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