2000 Toyota Tundra PO120, PO121, and PO420 Codes - Loss of Throttle Response After Restart
My wife's 2000 Toyota Tundra with a 4.7L V8 engine and 180,000 miles is experiencing complete loss of throttle response except when flooring the gas (WOT). After shutting down the engine and restarting it, the vehicle typically runs normally. The onboard diagnostic system shows persistent trouble codes: PO120, PO121, and PO420. I've recently replaced the oxygen sensors, but the issue persists. My current suspicion is that the throttle position (TP) sensor or catalytic converters may be faulty. However, I'm concerned about spending money on unnecessary repairs and want to identify the root cause. Are there any other potential solutions or diagnostic steps I should consider before replacing these components?
You're on the right track with checking the TP sensor and catalytic converters. However, PO120 and PO121 are often related to throttle position sensor issues or wiring problems—verify the sensor signal and connections first. Also, consider a scan tool to check for live data and intermittent faults before replacing parts. Good luck, and please update us on your findings.