PO402 code on '96 Explorer

- R
- Richard D
  
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posted
20 years ago

Thu, Aug 28, 2003 10:50 PM

My '96 Explorer has a 402 code problem. I've done some troubleshooting and have found...

1) Vacuum Solenoid resistance is good 2) Power getting to DPFE sensor 3) Vacuum to the EGR valve is there, but it feels like it's pulsing. Is this normal? 4) Vacuum doesn't appear to increase when you go to mid-throttle (2000-2200RPM) 5) I hooked up a new EGR valve to the vacuum line and the diaphragm is not moving at all, even at 2000-2200RPM. 6) DC voltage from the PCM to the solenoid is anywhere from 12.57vdc at idle to 13.15vdc at 2000RPM.

Any ideas?

Thanks,

-Richard

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- IK
  
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posted
20 years ago

Fri, Aug 29, 2003 4:02 AM

A common source of this is a bad DPFE. If you have access to a decent scanner, you can disconnect the tubes, and read the voltage with the key on and engine NOT running. If it indicates much more than a fraction of 1V, it's bad. Even if you don't have a scanner, you can still measure the DPFE output voltage by poking the brown/light green wire.

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- Jim Warman
  
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posted
20 years ago

Fri, Aug 29, 2003 7:04 PM

I agree with IK.... EGR flow codes are *usually* the result of a faulty DPFE....... The reason you can feel a it of vacuum at the line is because the EVRV is a duty cycle solenoid....... even though it is (for all intents and purposes) closed, the PCM is still grounding the solenoid "X" times per second with "OFF" time being about 99%. If we don't feel this little "tickle" of vacuum, we might suspect a vacuum probelm or a problem with the EVRV and/or it's circuit.

-- Jim Warman snipped-for-privacy@telusplanet.net

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- Richard D
  
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posted
20 years ago

Sun, Aug 31, 2003 3:00 AM

Thanks for the replies. I tried applying vacuum to the current EGR at idle and just as expected, the engine faltered. I assume since the DPFE is telling the PCM that the flow is excessive, that's why the new valve I tried never actuated under mid-RPM. Thanks!