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Q: Check engine light on.

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I have a 95 I6 4.9L with a check egine light on (turns on and off speratically). I had a guy scan with a computer and got a P0171, and another evp ept voltage low. I bought and changed the O2 sensor, as well as the canister purge valve (w/new hoses), per advice. I then figured out how to run the on board EEC-IV using the CIL and got codes: 327 Electronic pressure transducer (EPT)/differential pressure feedback exhaust (DPFE) sensor/electronic vacuum regulator (EVR) 522 Neutral/drive switch (NDS) 512 Keep alive memory (KAM) fault 111 All systems OK Replaced both battery terminal ends and a new battery. I've checked EGR Vacuum Solenoid for carbon buildup, but was clean. Intake manifold, throttle body gasket replaced. I have checked all other hoses for a vac leak using a can of starting fluid but all seems fine. Not to sure where to go from here. Thanks in advance for your help

My car has 268000 miles.
My car has a manual transmission.

The testing you did using the CIL may not have been done correctly. During these tests you will need to cycle the clutch and accelerate the engine when the separator codes were received. This is done with a superstar 2 or NGS tester or equal. The test without a proper tester may not work correctly. The code 327 may be a good code but the others may not. I suggest having the DPFE checked using pinpoint tests with a vacuum pump to see if the EGR valve sticks when opening. If the valve sticks, and then pops open can cause the code. I recommend having a certified technician scan the computer for codes and inspect the vehicle in person in order to have this accurately diagnosed and repaired.

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