DTC 1406 on a '96 SL-1 (with rusty rear doorsills)

I have a '96 SL-1 with the Service Engine Soon light on. I bought a
cheap code reader and it comes up with 1406. The book with the reader
says that is "Differential Pressure Feedback EGR (DPFE) Sensor
Downstream Hose Off or Plugged". Which do they consider downstream,
the engine side or the exhaust side? The hoses appear fine. I do have
a rusty exhaust pipe that is leaking, though. Could the reduced
backpressure cause this code? If replacing the pipe will fix it
problem, I'll hold off on fooling with the EGR (since it's about $150
and I have to fix the pipe anyways).
Thanks,
Buster

 

That's the wrong code description - P1xxx codes are manufacturer-specific,
GM doesn't use a DPFE setup - that sounds like a code for a Ford. P1406 for
GM seems to be a problem with the EGR pintle position (actual pintle
position as indicated by the sensor inside the EGR valve doesn't match the
commanded position).

 

OK, if that's the case, then my leaky exhaust pipe reducing
backpressure would have no bearing on this problem, right? Do I have
to replace the EGR valve or are they repairable?
Thanks,
Buster

 

I don't see the exhaust pipe affecting that. However, those linear EGR
valves tend to be somewhat pricey, you might want to get someone to take a
closer look at it with a scan tool and compare the EGR valve position
readings to make sure that's what's going on. It probably is the valve
that's gone bad though. It's possible it's just jammed with a piece of
carbon or something, but I wouldn't count on it.

 

Actually, that's the code for rusty rear doorsills.