Q: My 2001 chevy venture shuts off on me at random times . A couple of days the check engine light was on so we hooked the computer u

It’s not unusual for code P0420 to come on, stay on for even a few days, and then just disappear. Then, months later, it might happen again (i.e., appear and disappear). If this is the circumstances you face, I would ignore the occurrence until the code is set for more than a few days. At that point, inasmuch as you would have a NON intermittent fault the fault causing the code to set will be identifiable. While it remains an intermittent fault it will be very difficult to find the cause without testing a large number of components on the engine. Diagnostic Trouble Code P0420 has many, many potential causes including a damaged muffler or leaks in the muffler, damaged exhaust manifold or leaks in the exhaust manifold, damaged exhaust pipe or exhaust pipe leaks, misfiring in the engine, oil contamination in catalytic converter, a faulty catalytic converter, a faulty engine coolant temperature sensor, faulty front oxygen sensor, faulty rear oxygen sensor, damaged oxygen sensor wiring, oxygen sensor wiring that is not properly connected, damaged oxygen sensor connectors, a fuel injector that is leaking, fuel pressure that is high, and other causes. The only way to determine which of these faults is the cause is through a diagnostic. If the code does become "permanent" please request a check engine light diagnostic - code P0420 and the responding certified mechanic will get this resolved for you.

It is not clear from your question if the stalling problem was resolved by installing a new fuel pump. If the problem was not resolved, such stalling could be caused by an intermittent electrical connection in the fuel or ignition system, a faulty mass airflow sensor, worn spark plugs, wires or defective ignition coil(s), inadequate fuel delivery or pressure (clogged fuel filter, injectors), a defective throttle position sensor, faulty idle air control valve, leaks in the EGR system, intake vacuum leaks, and so forth. If you request an engine stalling/rough idle diagnostic the responding certified mechanic will get this resolved for you promptly, too. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.