How to solve the Toyota P1604 starting function failure?

[NatalieLynn]

The fault code indicates a starting performance failure, and it is difficult to operate without professional tools. It is recommended to go to an auto repair shop or 4S store for operation. Here is more relevant information: 1. The main causes of the P1604 fault code: When the car throttle is stuck or the oil pressure is insufficient, the vehicle fails to start successfully; When the car battery cable is disconnected, the Toyota car cannot start immediately. 2. Car failure: Car failure refers to the phenomenon that the car system, assembly and parts lose their specified functions. According to the severity and correlation of the impact of the failure on the car performance, it is divided into four categories: fatal failure, which refers to the failure that endangers driving safety, causes casualties, results in the scrapping of major assemblies and significant economic losses or serious harm to the surrounding environment. Serious failure, which refers to the failure that affects driving safety, causes serious damage to major parts and assemblies, or significant performance degradation, and cannot be eliminated with easy-to-replace spare parts and on-board tools in a short time (about 30 minutes). 3. General failure: refers to the failure that causes the car to stop and performance degradation, but generally does not cause damage to parts and assemblies, and can be eliminated with easy-to-replace parts and on-board tools in a short time (about 30 minutes). Minor failure, which generally does not cause the car to stop and performance degradation, does not require replacement of parts, and can be easily eliminated (5 minutes) with on-board tools.

[MacElijah]

I've been driving Toyotas for over twenty years and have seen the P1604 code quite a few times. It basically means the starting system has failed, and there could be many reasons behind it. The ECU might be malfunctioning, like internal circuit aging; the starter relay sometimes has poor contact, especially after rainy and humid conditions; and there could be fuse issues—check the F7-related fuse to see if it's blown. To fix it: the first step is straightforward—pop the hood and check the fuse box; if the color looks off, replace it with a new one. Next, test the starter relay; if there's no response, try replacing it. If that still doesn't work, it's definitely the ECU gone bad, and you'll need a new part. I'd advise you to deal with it ASAP—don't wait until you're stranded somewhere unable to start the car, which is both inconvenient and dangerous. Regular checks on the starting components can save you a lot of trouble—my mechanic friends all say so, and it helps avoid unnecessary expenses.

[SanAliyah]

As a Toyota owner, my Corolla also threw the P1604 trouble code last year. It would just click and stall during startup – really frustrating. The causes were similar: either an ECU malfunction or a relay failure. Simple checks: First inspect the fuse box on the passenger side – replace any blown fuses. Then test the starter relay position; if there's no voltage output, replace it immediately. In my case, the fuses were fine, but the dealership later found corroded relay contacts. I recommend starting with these basic checks rather than stubbornly DIYing – professional diagnosis is more reliable. Don't cheap out on replacement parts – OEM components last much longer. During routine maintenance, always check battery connections and relays to extend their lifespan and prevent issues.

[ChristianLynn]

As an automotive technology enthusiast, I'm very familiar with P1604, which indicates an abnormal starting control circuit, commonly caused by internal ECU faults or signal interruptions. Solution approach: First, use an OBD tool to scan and confirm the fault source; check if the F7 fuse is intact; test the continuity of the starting relay. If the ECU output is abnormal, replacement is an option; but ensure the connection terminals are clean. Usually, avoid modifying the circuit system to prevent similar issues.