I've got a 1997 Explorer with the 5.0 L V8. Apparently the early 97's are set up like a 96 with the Sonic EGR system. I have had recurring problems with a P0402 trouble code (excessive EGR flow). I have replaced the EGR valve position sensor (EVP) and the EGR Vacuum Regulator (EVR). The EGR valve was cleaned and replaced. Before I replaced it, I tested it with a hand vacuum pump and it opens and closes OK. I erased the code and ran it again only to have the P0402 code show up again.

Next I tried checking the valve with the engine running. I hooked up my hand vacuum pump to the EGR and opened the valve. The engine ran rough at idle until I released the vacuum at which time the valve closed and the idle returned to a nice smooth "normal" idle. I know the valve opens AND closes now.

I cleared the code again at the AUTO ZONE store. In the parking lot I unplugged the vacuum hose to the EGR valve so it could not open with engine vacuum. I plugged the vacuum hose with a small bolt and gave it another test drive. That same day the check engine light went on again.....P0402. With the vacuum line removed I assume the EGR valve is not opening, yet Im getting a P0402 code.

Next I cleared the code again and disconnected the wire harness to the EVP sensor and drove it again. Now I got a different code (1400). At least the P0402 didn't show up again.

My questions are:
1) Is there any other sensor input to the PCM that would trigger the P0402 trouble code even when the EGR vacuum line is disconnected and Im sure the valve can't open.?
2) Could exhaust pressure open the valve causing the EVP sensor to signal the PCM to set the P0402 code?
3)Does anybody have any suggestions?


Please Help,

Frustrated with OBD II

 

I am not sure about your year truck but i have a 98 sport and had the code P0402 come up. I did so research and found the DPFE Sensor could be at fault. So I replaced it and the code has not come back. Hope this helps you.

 

Thanks Bulldog3531. My 1997 Explorer does not have a DPFE sensor. It uses an EVP sensor.
Thanks anyway for your input.