When your car refuses to start and just won’t turn over, it’s a frustrating situation. You might be wondering, “Can I use a car scanner to figure out why my car won’t turn over?” The answer is yes, a car scanner can be a helpful tool, but it’s not always the only solution. Let’s explore how a car scanner can assist and when you might need to dig deeper with manual checks.
A car scanner, also known as an OBD-II scanner or diagnostic scanner, is designed to read data from your car’s computer system. It primarily communicates with the Engine Control Unit (ECU) and can retrieve diagnostic trouble codes (DTCs) related to various systems like the engine, transmission, and emissions. These codes can give you a starting point for diagnosing issues.
However, when your car won’t turn over—meaning the engine isn’t cranking at all—the problem might lie in areas that a generic car scanner doesn’t directly monitor for starting issues. The reason your car won’t crank could be due to a lack of power to essential components, like the fuel pump.
Take the fuel pump, for example. For it to work, several things need to be in order. As illustrated in the wiring diagrams below, the ECU, ignition switch, and various relays must function correctly to supply power to the fuel pump.
If your car is not turning over and you suspect a fuel delivery issue, a car scanner might not immediately pinpoint a problem in the fuel pump’s power circuit if there isn’t a sensor directly reporting a fault that generates a standard DTC related to cranking. In such cases, you might need to manually trace the power flow using a multimeter and wiring diagrams like these:
Following the diagrams, you can check for 12V at different points in the fuel pump circuit. For instance, the light blue with red stripe (L-R) wire should have 12V from the battery’s EFI fuse. After the EFI relay, the white with light blue stripe (W-L) wire should be powered with the key turned to the “on” position. If voltage is missing at these points, it indicates a problem upstream, possibly with the ECU, relays, wiring, or ignition switch.
While a car scanner might not directly show a “no fuel pump power” code in this scenario, it can still be valuable. It could reveal codes related to other engine management systems or sensors that are indirectly preventing the car from starting. For example, issues with the crankshaft position sensor or immobilizer system, which a scanner can often detect, could also prevent the engine from turning over.
In conclusion, while a car scanner is a useful first step when your car won’t turn over, it might not always provide the definitive answer, especially for electrical power supply issues. If the scanner doesn’t reveal obvious codes, especially related to starting or engine management, manual troubleshooting with wiring diagrams and a multimeter, focusing on components like relays, fuses, and wiring to the fuel pump and ignition system, becomes essential to diagnose why your car won’t turn over. Remember to consult your vehicle’s service manual for accurate wiring schematics and component locations to effectively diagnose the issue.
