I have a 95 Crown Vic with 65K miles. A few days ago the CEL light came on
(steady, not blinking). The repair shop read a code of P0401. After
some more testing the DPEF sensor was found to be faulty and was
replaced. This was followed by a "quick test (OK)" and a "road test
After I had picked up the car, the light came on again after about 2
miles. I did some reading on the internet and found reports
indicating that these symptoms are often caused by plugged tubes that
route the exhaust from the EGR to the intake manifold. I brought the
car back to the shop with a print-out of the internet reports.
The code was again P0401. The following were checked:
- electrical part of circuit (OK)
- EGR solenoid operation (OK)
- EGR valve operation, diaphragm (OK)
- EGR valve effect on engine (could not notice any change)
- pressure from reference tube at EGR exhaust tube (slight pressure
Then the EGR tube was cleaned. The EGR operation was "checked as per
manual and found to be normal". There was a "road test extended
monitor DPFE sensor parameters and percentage of EGR opening:
operation is normal.
The PCV (not EGR) hose was found to be collapsing at throttle body and
was replaced. The PCV was also replaced.
The invoice took into account that I had already paid to have this
problem fixed and that this was a "redo".
However, after I had picked up the car and driven 12 blocks the light
came on again. Any idea as to what is going and any recommendation
(besides the obvious)? TIA