Introduction:
The B1248 diagnostic trouble code (DTC) indicates a fault within the passenger's seatback auto-glide rearward switch circuit, specifically a short to ground. This means the electrical circuit controlling the rearward movement of the passenger seatback is unintentionally making contact with the vehicle's ground, causing the system to malfunction. Addressing this issue promptly is important for restoring full functionality of the seat adjustment system and ensuring passenger comfort and safety.
Table: B1248 DTC Breakdown
| Category | Description | Possible Causes |
|---|---|---|
| DTC Definition | Passenger's Seatback Auto glides Rearward Switch Circuit Short to Ground | 1. Short to Ground: A wire in the circuit is making direct contact with the vehicle's chassis or other grounded metal component. 2. Faulty Switch: The rearward switch itself is internally shorted to ground. 3. Damaged Wiring: Insulation on the wiring is damaged, exposing the wire and causing it to contact ground. 4. Connector Issues: Corroded or loose connectors within the circuit, potentially creating a path to ground. 5. Seat Control Module (SCM) Malfunction: Although less likely, the SCM itself could be malfunctioning and falsely reporting the short. 6. Pinched or Broken Wires: Wires may be pinched or broken due to seat movement, leading to short circuits. |
| Symptoms | 1. The passenger seatback may move rearward unexpectedly or not move at all. 2. The auto-glide function may be disabled. 3. The seat control system may be unresponsive. 4. The vehicle's computer may store the B1248 DTC. 5. Other seat functions may be affected (depending on vehicle design). 6. Fuse blowing (repeatedly, if a severe short). | N/A |
| Troubleshooting & Repair | 1. Visually inspect the wiring harness and connectors associated with the passenger seatback auto-glide rearward switch. 2. Use a multimeter to check for continuity between the switch circuit and ground. 3. Isolate the switch and test it independently. 4. Check for voltage at the switch connector (with the ignition on). 5. Inspect the wiring harness for damage or chafing. 6. Test the continuity of the wiring from the switch to the seat control module. 7. Consult the vehicle's service manual for wiring diagrams and specific testing procedures. 8. If all wiring and components test good, suspect a faulty Seat Control Module (SCM). | N/A |
Detailed Explanations
DTC Definition: Passenger's Seatback Auto glides Rearward Switch Circuit Short to Ground
This code specifically identifies that the electrical circuit responsible for activating the passenger seat's rearward auto-glide function is experiencing an unwanted connection to the vehicle's ground. This "short to ground" disrupts the normal flow of electricity within the circuit, causing the system to malfunction. The diagnostic system recognizes this deviation and stores the B1248 code.
Short to Ground:
A short to ground is an electrical fault where a wire or component within a circuit unintentionally makes direct contact with the vehicle's metal chassis or another grounded part. This creates a low-resistance path for electricity to flow, bypassing the intended components and creating a high current flow. This high current can damage components, blow fuses, and cause erratic system behavior. In the context of the B1248 code, a wire in the seatback auto-glide rearward switch circuit is touching a grounded metal surface.
Faulty Switch:
The rearward switch itself, located on the seat, could be internally defective, causing a short circuit. This means that internal components within the switch are making unintended contact with ground, even when the switch is not being actively pressed or activated. Testing the switch in isolation, outside of the vehicle's wiring harness, is crucial to verify its integrity.
Damaged Wiring:
The wiring harness connected to the rearward switch is susceptible to damage from chafing, bending, or exposure to the elements. Over time, the insulation surrounding the wires can wear away, exposing the bare conductors. If these exposed wires come into contact with a grounded metal surface, a short to ground will occur. Careful visual inspection of the entire wiring harness is essential.
Connector Issues:
Electrical connectors are critical for maintaining proper connections within the circuit. Corrosion, loose connections, or damaged connector pins can disrupt the flow of electricity and potentially create a path to ground. Corrosion can build up on the contacts, providing a conductive path to the grounded metal of the vehicle's frame. Loose connections can cause intermittent shorts as the wires vibrate.
Seat Control Module (SCM) Malfunction:
The Seat Control Module (SCM) is the electronic control unit that manages the various seat functions, including the auto-glide feature. While less frequent than wiring or switch problems, the SCM itself could be malfunctioning and incorrectly interpreting the signals from the rearward switch circuit, leading it to falsely report a short to ground. Before replacing the SCM, thoroughly investigate all other potential causes.
Pinched or Broken Wires:
The movement of the seat can, over time, pinch or break wires within the seat harness. This is especially common in areas where the harness flexes frequently. Pinched wires can have their insulation damaged, leading to a short to ground when the exposed wire contacts the seat frame or other grounded components. Broken wires can also create intermittent shorts as they make and break contact with ground.
Symptoms:
The symptoms associated with a B1248 code can vary depending on the severity of the short and the specific vehicle's design. Common symptoms include the passenger seatback moving rearward unexpectedly, the auto-glide function being disabled entirely, the seat control system becoming unresponsive, and the vehicle's computer storing the B1248 DTC. In some cases, other seat functions might also be affected. A frequently blowing fuse in the seat control circuit is a strong indicator of a severe short to ground.
Troubleshooting & Repair:
Troubleshooting a B1248 code requires a systematic approach. Begin with a visual inspection of the wiring harness and connectors associated with the passenger seatback auto-glide rearward switch. Look for any signs of damage, corrosion, or loose connections. Use a multimeter to check for continuity between the switch circuit and ground. Isolate the switch and test it independently to rule out an internal short. Check for voltage at the switch connector with the ignition on. Inspect the wiring harness for damage or chafing. Test the continuity of the wiring from the switch to the seat control module. Consult the vehicle's service manual for wiring diagrams and specific testing procedures. If all wiring and components test good, suspect a faulty Seat Control Module (SCM).
Frequently Asked Questions
What does the B1248 code mean?
The B1248 code indicates a short to ground in the passenger seatback auto-glide rearward switch circuit, disrupting the normal electrical flow. This means the wiring has an unintended connection to the vehicle's chassis.
What are the common causes of the B1248 code?
Common causes include damaged wiring, a faulty switch, corroded connectors, or a malfunctioning Seat Control Module (SCM). Identifying the root cause is crucial for effective repair.
How do I fix a B1248 code?
Fixing a B1248 code involves visually inspecting the wiring, testing the switch and wiring for shorts, and potentially replacing damaged components. Refer to the vehicle's service manual for specific instructions.
Can a bad seat switch cause a B1248 code?
Yes, a faulty seat switch can cause a B1248 code if it is internally shorted to ground. Testing the switch in isolation is important to rule this out.
Is it safe to drive with a B1248 code?
While driving with a B1248 code may not be immediately dangerous, it's advisable to address the issue promptly as it could affect passenger safety and comfort. The seat may move unexpectedly or not function properly.
Conclusion
The B1248 DTC, indicating a Passenger's Seatback Auto glides Rearward Switch Circuit Short to Ground, requires a systematic approach to diagnose and repair. Thorough inspection of wiring, connectors, and the switch itself is essential, and consulting the vehicle's service manual is highly recommended for accurate troubleshooting and repair procedures.