Body, generic

B0339 Rear Seat Heater Circuit

Check engine lightUsually off

EmissionsNot relevant

Drive cycleNot required

Limp modeNo

B0339 shows up neither in the public code lists nor in published service material. Rear seat heating is an option on larger cars; the GM-built 2011 Saab 9-4X with heated rear seats has a dedicated control module behind the rear backrest. It feeds both mats through a common supply, regulates by switching their ground with PWM and checks current and voltage every 10 s: B2425/B2430 0D mean element resistance too high, 0B/0E too much current or too little resistance. Each rear seat also carries an NTC sensor (B1925/B2170), and B2345 13 reports the shared disable line. US5229579A shows why such controllers shut off on a short or an open circuit.

Likely causes

Heating mat in a rear seat cushion broken

Connector damaged when the rear seat was folded or removed

Rear seat heating control module or its supply faulty

Seat temperature sensor implausible so heating is disabled

Symptoms

One or both rear seat heaters stay cold
Rear seat heating indicator flashes or goes out

Repair estimate

DifficultyMediumWorkshop job

Parts and labour€80–700

Time0.5–4 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

seat heater elementrear seat wiring

Related codes

B0335 B0337

References: saabwisonline.com, saabwisonline.com, saabwisonline.com, patents.google.com.