B1979

Passenger Seat Rearward Switch Circuit Short to Battery

Body Chassis/Safety Seat Control 🟢 Low — Fix at next service ✅ Safe to Drive
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What This Actually Means

In plain language — no jargon

The passenger seat's rearward movement switch is sending a constant maximum voltage signal to the ECU, like a stuck light switch always at full brightness. This indicates the circuit is shorted directly to the vehicle's battery power instead of operating normally.

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Symptoms You May Notice

3 known symptoms for this code
Seat adjustment warning light illuminated on dashboard
Passenger seat rearward function inoperative or behaves erratically
Possible loss of other seat adjustment functions
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How Your ECU Detects This

Technical sensor logic and voltage thresholds

The ECU monitors the voltage level on the passenger seat rearward switch circuit, expecting variable signals between ground and battery voltage as the switch is activated. When the circuit shorts directly to battery voltage, the ECU detects a constant high voltage state that never returns to normal logic levels, triggering the fault code.

Voltage & Parameter Thresholds

ParameterNormal RangeFault Condition
Switch Circuit Voltage 0-5V variable, cycling with switch activation Continuous 12V battery voltage
Circuit Resistance Variable 0-4.7kΩ depending on switch state Near 0Ω (short to battery)
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Diagnostic & DIY Fix Guide

Check these in order — from cheapest to most complex
1
Wiring harness connector
Inspect and reseat the passenger seat switch connector at the seat base to eliminate poor connection causing false battery voltage detection.
2
Switch wiring and routing
Check for pinched, abraded, or damaged wiring near the seat track that may be grounding to battery positive accidentally.
3
Rearward switch assembly
Replace the faulty switch unit if visual inspection reveals internal contact damage or melting indicating short failure.
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When to See a Professional Mechanic

Not all fault codes are safe to DIY

Code B1979 is a low-severity fault. Your vehicle is generally safe to drive to a workshop for diagnosis. However, do not ignore it indefinitely — low-severity codes often indicate developing problems that become expensive if neglected. Book a diagnostic appointment within 2–4 weeks. If you notice any additional symptoms (rough running, power loss, unusual smells), treat it as higher priority.

Safety note: OBD-II codes identify the system or circuit where a fault was detected — they do not always identify the exact failed component. A professional mechanic using live sensor data will diagnose the root cause more accurately than replacing parts based on the code alone.
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How to Clear Code B1979

What happens after you fix the fault

Once the fault is repaired, B1979 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.

The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.

✅ Safe to Clear When
  • Fault has been diagnosed and repaired
  • You want to confirm the repair worked
  • Code appeared after a sensor was cleaned
⚠️ Do Not Clear When
  • Preparing for an emissions/PUC test
  • Root cause is still undiagnosed
  • Check engine light is flashing
Emissions test note: Clearing codes resets OBD readiness monitors. Most vehicles need 50–100 km of mixed driving before monitors complete. Do not clear codes immediately before an emissions or PUC inspection.