Answer
Oct 09, 2025 - 03:09 PM
It sounds like your 2004 Tundra’s issue is related to the immobilizer or ignition circuit, especially since it starts and then immediately shuts off when you bypass the ignition. When a Toyota’s security system doesn’t recognize the key signal from the transponder chip, it allows the engine to fire briefly, then cuts fuel or spark right after — exactly like what you’re describing. This could be due to a faulty immobilizer module, a bad key transponder, or an issue with the ignition switch wiring that prevents the ECM from seeing the proper “key-on” signal. Other possibilities include a shorted ignition relay or a damaged wire in the ignition circuit. Try using a spare key if you have one, and check whether the security light on the dash stays on or flashes after starting — that’s a key clue. If it does, you’re likely dealing with an immobilizer problem that will require reprogramming or replacing the ignition cylinder or key chip.
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