My friend's '96 LHS has an engine light that comes on intermittently. The car recently failed inspection and gave out a P0401 error code (insufficient EGR gas recirculation). What is the procedure for tracking down the source of this problem?
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when was the last time the egr valve was replaced ?? could be restricting flow .... to the system... thus clogging up.......... p0401- Insufficient EGR flow
then after replacing it,,, disconnect battery for about 20 minutes and it should reset the system.
P0401=EGR valve insufficient flow P0700=transmission control system malfunction P1739=transmission control module controller circuit
Get the EGR valve checked. It may be that a vacuum line is off. But worst case, say you need a new EGR valve. You can price one at autozone.com. Then find out what a shop would charge for labor to put it in. The transmission codes may be intermittant faults. If your car seems to be running fine, reset the codes and they may not come back until after your test, if ever. If the codes come right back, you'll have to take it to a transmission shop for check out. Any major auto parts store has a code reader that can reset your codes for free.
Just to be clear, have all your work done and then reset your codes. Then you will have to drive your car normally for a few days before taking your DMV inspection. There is a test they will run to see if enough drive cycles (a start, run, and shut down=one cycle) have been accomplished after a code reset. This prevents people from resetting the codes and immediately taking the test without any work being done.
P0401 indicates that the Exhaust Gas Recirculation Flow Insufficient Detected. This can be because EGR is faulty . As you have replaced this then the problem must be with the vacuum line . EGR valve vacuum line which can be broken or blocked. The vacumn ine must bbe checked for leaks or any blocks using an vacumn pump connected the line.
P0420 indicates that the down stream oxygen sensor reading is not steady and it is connected with the code P0401.
a blinking eng light usually comes with power loss and shaking as the vehicle is misfiring. Scan the vehicle's computer as this would give you a starting point. Codes P0300, P0301, P0302, P0303... would indicate misfires detected in particular cylinders inspect ignition components and repalce as needed