B2885

Code

Generic B — Body

Seat Heater Circuit Fault

Brand: Generic

Type: B — Body

Views: UK: 14 EN: 29 RU: 16

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Page language: EN

Causes

Open circuit in heater element or wiring
Short to ground or short to battery
High resistance connection or corroded connector
Blown fuse or tripped thermal/inline fuse
Faulty seat heater switch or control module
Water intrusion or physical damage to seat cushion/heating mat

Symptoms

Seat heater does not turn on for the affected seat
Seat heater works intermittently or only on certain settings
Indicator lamp for seat heater does not illuminate or flashes
Fuse blows repeatedly when heater is turned on
Burnt odor from seat or visible damage to seat cover/foam
Related diagnostic trouble code(s) stored in occupant/seat module

What to check

Read and record DTC(s) and freeze frame with an OEM-level scan tool
Verify vehicle battery voltage (should be ~12–14 V) during testing
Inspect fuses and relays for the seat heater circuit
Visually inspect seat upholstery and connector areas for moisture/damage
Perform resistance/continuity checks of heater element and wiring harness
Check for proper ground at seat ground point and at module

Signal parameters

Supply voltage to heater circuit: nominal battery voltage (approx. 12–14 V)
Heater element resistance (typical range varies by vehicle): often a few ohms to tens of ohms — consult vehicle-specific data
Control signal: on/off or PWM drive from seat control module; PWM frequency and duty vary by manufacturer
Current draw: commonly several amps (typical single-seat range ~2–15 A depending on seat and setting)
Thermistor/temperature sensor resistance (if equipped): varies with temperature — consult service data

Diagnostic algorithm

Step 1 — Read codes and note which seat is affected. Clear code and attempt a function test to see if code returns.
Step 2 — Verify battery voltage at the fuse/circuit with heater switch ON. If low, investigate supply or charging system before proceeding.
Step 3 — Inspect fuse(s) and relays for the seat heater circuit. Replace any blown fuses and retest. If fuse blows again, proceed with wiring checks.
Step 4 — Visually inspect seat area for water intrusion, damaged upholstery, or exposed wiring. Unplug connectors and inspect for corrosion or bent terminals.
Step 5 — With ignition OFF, measure resistance of the seat heating element between its harness pins. Compare to vehicle-specific spec; infinite/very high = open, near 0 = short.
Step 6 — Check continuity from the harness connector back to the control module and battery/fuse. Wiggle wiring around seat rails to reproduce intermittent faults.
Step 7 — Measure control output from seat control module while operating heater (use backprobe with module energized). Look for switched battery voltage or PWM output consistent with spec.
Step 8 — If element and wiring are good but no drive signal from module, inspect module grounds and inputs (seat switch, temp sensor, occupant detection) and repair/replace module as required.
Step 9 — If heating element is damaged, repair or replace the heating mat and any inline thermal fuses or sensors. After repair, clear codes and verify operation across all settings.
Step 10 — After repair, perform a final scan to ensure no further DTCs and confirm the circuit does not blow fuses under normal operation.