B1979 — Passenger Seat Rearward Switch Circuit Short to Battery

The diagnostic trouble code B1979 indicates a problem within the circuit controlling the passenger seat’s rearward adjustment switch. This code suggests there is a short circuit, specifically a direct connection between the switch circuit and the vehicle’s battery voltage. This can interfere with the normal operation of the seat adjustment system, and potentially impact other electronic systems connected to this circuit.

Please note that labels for this fault code can vary between different vehicle manufacturers. Always refer to the specific manufacturer’s documentation for precise terminology.

Fast Facts

System affected: Passenger Seat Adjustment Circuit
Severity: Moderate – may affect seat adjustability and other connected systems
Main symptoms: Passenger seat may not move, warning lights, or possible electrical anomalies
Driveability: Limited — can usually drive but with caution

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Manufacturer variations for trouble code B1979

The specific label or diagnostic identifier for B1979 can differ depending on the vehicle manufacturer. Some OEMs may assign different codes or descriptions for similar issues. Here is a list of known label variations:

Volkswagen / Audi: Rear Seat Switch Circuit Short to Battery
Ford: Passenger Seat Rearward Switch Circuit Shorted
BMW: Passenger Seat Adjustment Circuit Fault
Mercedes-Benz: Seat Adjustment Circuit Short Fault

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What does trouble code B1979 mean?

In simple terms, this code points to an electrical problem within the circuit that controls the passenger seat’s rearward adjustment switch. The vehicle’s Engine Control Unit (ECU), which is the central computer managing various electronic systems, constantly monitors this circuit for unexpected conditions such as short circuits or open circuits.

The trigger for this code occurs when the ECU detects a short-to-battery condition, meaning that the wiring or switch is improperly connected directly to the battery voltage. This situation often results from damaged wiring, a faulty switch, or poor previous repairs.

Typically, the appearance of this code happens during routine diagnostic checks or immediately after an electrical fault such as wiring damage or during seat movement attempt.

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Severity and risks of trouble code B1979

The severity of B1979 is considered moderate. While it may not immediately prevent the vehicle from operating, it poses potential risks such as electrical damage, further circuit issues, or malfunctioning of the seat adjustment system. Persistent shorts can also cause blow fuses, which might affect other electrical components.

Will this issue irreparably harm the vehicle? Typically, no. However, ignoring the fault can lead to additional electrical problems, increased repair costs, and inconvenience. Overall, the vehicle can usually be driven but should be diagnosed and repaired promptly to prevent further complications.

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Symptoms of trouble code B1979

Drivers or technicians might notice several signs indicating a problem within the passenger seat adjustment system. These symptoms may not be severe but can influence comfort and driveability:

The passenger seat may not move forward, backward, or recline as intended.
The seat adjustment switch may be unresponsive or intermittently work.
Possible electrical warning lights on the dashboard related to seat or general electrical faults.
Fuses related to the seat adjustment system may blow during operation.
No physical damage is apparent to the wiring or switch, but electronic faults are evident through diagnostics.

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Most likely causes of trouble code B1979

This fault is generally caused by issues related to wiring integrity, switch integrity, or electrical shorts. The probable causes are listed in order of commonality:

Short-circuited wiring or connector — Damage or insulation failure leading to the circuit touching battery voltage.
Faulty passenger seat rearward switch — A defective switch that internally causes a short circuit.
Corroded or damaged connectors — Moisture, dirt, or corrosion disrupting proper electrical contact.
Blown fuse or relay related to seat adjustment circuit — Overcurrent due to a short circuit can blow protective components.
Underlying wiring harness issues or previous repairs — Poor splices, improper re-wiring, or damaged wiring.

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How to diagnose trouble code B1979

Diagnosing B1979 involves systematic inspection of the seat adjustment system’s electrical circuit. Here are some generic steps to approach the diagnosis safely:

Visual inspection: Check the wiring harness, connectors, and switch for visible damage, corrosion, or pinched wires.
Verify fuse status: Ensure that the fuse related to the seat adjustment circuit is intact and not blown.
Test the switch: Use a multimeter to verify that the passenger seat rearward switch works correctly and does not show internal short circuits.
Check wiring continuity: With the circuit disconnected, perform a continuity test between the switch connector and the power source to identify shorts or open circuits.
Live data reading: Use an OBD-II scanner capable of reading seat system data to check for anomalies while operating the switch.
Inspect for shorts to the battery: Use a multimeter to measure resistance and check if the wiring or switch is directly shorted to the positive terminal of the battery.

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Possible repairs for trouble code B1979

Once the root cause has been identified, repairs can proceed. The nature of repairs varies from simple fixes to more involved interventions, often requiring a professional skillset.

Replacing damaged wiring or connectors — Basic repair. Necessary if insulation is damaged or wiring is severed.
Replacing the faulty switch — Usually a straightforward repair but may involve removing panels or components.
Repairing or replacing the wiring harness — More advanced and requires proper harness replacement if damage is extensive.
Replacing blown fuses or relays — Basic, but essential to ensure circuit protection is restored.
Addressing underlying electrical problems — Such as fixing corrosion or ensuring secure connections; may involve cleaning contacts or tightening connectors.

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Vehicles commonly associated with trouble code B1979 in Europe

While this fault can occur on various models, certain vehicle brands and models tend to experience this issue more frequently due to design or wiring characteristics. The most affected vehicles are often within certain brands or engine families:

Note: Specific data is based on available diagnostic reports and may vary. Always consult manufacturer-specific resources for precise vehicle applications.

Volkswagen Group: Various models across Volkswagen, Audi, Skoda, and Seat
Ford: Several passenger vehicles with powered seat systems
BMW: Models with advanced seat electronics
Mercedes-Benz: Vehicles with electronically controlled seats

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Frequent mistakes with trouble code B1979

Diagnosticians and technicians often make mistakes that can prolong repair time or lead to incomplete fixes. Awareness of these pitfalls ensures a more accurate diagnosis:

Overlooking simple visual checks: Failing to inspect wiring, connectors, and fuse status.
Replacing components without testing: Swapping switches or wiring without proper testing can be costly and ineffective.
Ignoring underlying causes: Focusing solely on the switch rather than wiring or circuit integrity.
Neglecting to review live data: Not using a scan tool capable of real-time data may lead to missed faults.
Assuming all faults are software-related: This fault is physical/electrical, so software update alone won’t resolve it.

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FAQ — trouble code B1979

Can this code disappear on its own? No, B1979 is caused by an electrical fault or hardware issue that won’t resolve without repair. Clearing the code may temporarily make it disappear, but if the root cause persists, it will likely return.

Can I keep driving? Generally, yes. The vehicle can often be driven, but caution is advised. The issue might prevent seat adjustment or cause electrical system disturbances. It’s best to have it diagnosed and repaired promptly.

Why does the code return after clearing? Because the underlying wiring or switch fault remains, causing the ECU to repeatedly detect the short to battery voltage and re-trigger the code upon reset or reinitialisation.