1998 Pontiac Transport Montana service engine
soon codes P1665, P0452 and P0440. The
service engine lite has been on since I bought the
car. I had the transmission replaced because 1st
and reverse were shot. And the van runs great,
but my gas mileage has gone way down and the
service engine lite wont shut off.

I replaced the transmission and replaced the gas
cap. The
front brakes and calipers were replaced
too. Could this be an oxygen sensor problem?

EVAP system vent solenoid circuit.
P0452 fuel tank pressure sensor circuit low
voltage. P0440 - general EVAP system problem.
Something in common with these 3 codes is the
fuse labeled  CAN VENT SO which stands for
Canister Vent Solenoid. If this fuse is blown, it will
cause all these codes. If fuse OK, then possibly a
problem at the fuel pump assembly connector on
top of the fuel tank.

Another area that can cause electrical problems
with these circuits is a pass-through harness
connector under the van. Sometimes it gets
corroded and can cause these codes.
2001 Pontiac Montana 3.4L Check engine light code P1639 and
P0452. Question = My 2001 Pontiac Montana has been revving up
anywhere from 1500 to 3000 rpms. Went to Autozone to have them
test it and got codes P1639 and P0452. I replaced the fuel pump a
couple months ago. What do these codes mean and how do I fix

The P0452 code is for the Fuel Tank Pressure Sensor, and the
P1639 is for the A/C Refrigerant Pressure Sensor. Both of these
sensors are on the same 5 volt signal circuit from the PCM, and that
is why both codes are set. There is something wrong that signal
circuit to one of those sensors and it is bringing the whole line down.

You could have pinched the wiring when you did the fuel pump,
since the fuel tank pressure sensor is located as part of the fuel tank
module you removed. I'd check that out first, although you will have
to drop the tank again. Also, there have been problems with the
body pass-through connectors on the underside of the van. If you
follow the fuel pump harness from the tank, you will see it leads to a
small bulkhead on the underside of the body. Check that connection
for corrosion, or water intrusion. If there is a problem with that area,
you will need to replace that entire connector assembly.

As for the revving up as you drive, I don't think your current codes
would cause that problem. You could have a transmission issue,
that would need further diagnosis.
Pontiac Transport and Montana EVAP System Codes

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