P0420 Fault on 1997 Jeep Grand Cherokee 5.2L: No Start, Full Power, and Diagnostic Code Persistence
I'm experiencing a puzzling issue with my 1997 Jeep Grand Cherokee 5.2L. The vehicle recently triggered a P0420 diagnostic code, which I had previously resolved by replacing the catalytic converter and oxygen sensor last year. However, this time, when I tried to start the car, it failed completely — no engine crank, no sound of movement, only dashboard lights and full electrical power. The check engine light illuminated immediately upon attempting to start. In past occurrences with P0420, the vehicle was still drivable. This time, however, there is absolutely no response from the engine at all. I'm concerned whether the P0420 code itself could be causing a no-start condition or if it's actually indicating a different underlying issue. Could this code be misleading or unrelated to the starting failure?
P0420 is generally not associated with complete no-start conditions. Let's first rule out basic electrical and mechanical issues. Have you scanned the vehicle for any other codes? If not, try using the key-on-off trick to retrieve stored codes without a scanner. Also, attempt starting the vehicle with the shifter in neutral (N) or gently wiggling the shift lever. Check if headlights and horn function — these indicate basic electrical continuity. If all systems are working, proceed with diagnostics.