Experiencing a sudden engine stall and a no-start condition in your 2018 WRX can be incredibly frustrating, especially when accompanied by a lack of power to the OBD2 port. This situation can be particularly puzzling after recent modifications or maintenance, such as performing a TGV (Tumble Generator Valve) delete and resetting the ECU. If you’ve encountered this issue, understanding the potential causes and systematic troubleshooting steps is crucial to getting your WRX back on the road.
One common scenario reported by WRX owners involves the car dying while driving at low speeds, followed by a complete inability to restart. Often, key symptoms include the fuel pump failing to prime, the starter not engaging, and crucially, no communication through the OBD2 port. This lack of OBD2 power is a significant indicator and points towards an electrical system malfunction rather than mechanical failure.
Several factors can contribute to this problem, particularly in modified vehicles. A frequent culprit is electrical fuse failure. Specifically, the SBF #5 fuse in the engine compartment and a 15A fuse in the passenger side compartment are known to cause these exact symptoms when blown. These fuses are often linked to the car’s vital systems, including the ECU, fuel pump, and OBD2 circuit. Short circuits, often stemming from damaged or exposed wiring, especially around O2 sensors, can lead to these fuses blowing.
Considering modifications like a TGV delete, it’s important to examine if any related wiring might be compromised. While TGV deletes themselves are generally safe when properly installed, the process involves disconnecting and sometimes bypassing factory wiring. If the connectors for the TGV system were not properly insulated after the delete, moisture or general wear and tear could potentially lead to a short circuit over time, especially if the vehicle has been exposed to damp conditions, as mentioned in some cases where issues arose after driving on wet roads.
Resetting the ECU, often done using an Accessport or similar device, is less likely to directly cause a major electrical failure. However, any electrical anomaly present beforehand might become more apparent or problematic after an ECU reset as the system re-initializes. It is more probable that the ECU reset simply coincided with, or perhaps slightly exacerbated, an existing underlying electrical issue.
Troubleshooting this no-start condition with no OBD2 power requires a methodical approach:
- Fuse Inspection: Begin with a thorough inspection of all relevant fuses. Focus on the SBF #5 and the 15A fuse mentioned earlier, but check all fuses in the engine bay, driver’s side, and passenger side fuse boxes. Visually inspect for broken filaments.
- Fuse Continuity Testing: Visual inspection isn’t always definitive. Use a circuit tester or multimeter to confirm continuity across each fuse. This ensures the fuse is actually conducting electricity.
- Relay Swapping: Relays control power flow to various components. Try swapping relays related to the fuel pump and ECU with identical relays in the fuse box to rule out relay failure.
- O2 Sensor Wiring Check: Inspect the wiring for both front and rear O2 sensors. Look for any signs of fraying, damage, or exposure, especially if a rear O2 sensor has been removed or replaced with a wideband sensor. Ensure any disconnected sensor connectors are properly taped off and insulated.
- TGV Delete Wiring Inspection: Re-examine the wiring and connectors related to your TGV delete. Confirm that all connections are secure and properly insulated, and that no wires are pinched or exposed.
If after checking these points the issue persists, more in-depth electrical diagnostics might be necessary, potentially involving tracing wiring diagrams and using a multimeter to check for voltage and continuity along the power circuits for the OBD2 port, fuel pump, and starter. While an ECU failure is less likely, it remains a possibility if all other electrical components and wiring are verified to be functioning correctly.
By systematically checking these areas, you can effectively diagnose the common causes behind a 2018 WRX no-start condition with no OBD2 power, particularly in the context of modifications like a TGV delete and recent ECU resets. Remember to prioritize safety when working with automotive electrical systems and consult a professional if you are uncomfortable with any troubleshooting steps.
