Pontiac Repair: 1999 Pontiac Montana computer codes, mass air flow sensor, mass air flow

Question
About a few weeks ago everything started to go wrong. First,
the fuel guage stays peg at empty after 15 seconds at full. I replaced the fuel pump assymbly with a new unit...no dice.

Then my ABS/TCS lights light up after van is started and stays on.
Then my "LOW COOLANT" light lit on, altho the system was flushed and Dexcool installed and bleeder valves bled and unit is full.

Then the "Check Engine light" lit on. Since I have this OBD2 code machine I pulled the codes and here's what it spat out:

P0102-mass air flow sensor circuit, low input...results: I
checked the three wires coming from the sensor and the PINK
one registers ZERO volts instead of the 12 volts require.

P0135-Oxygen sensor heater ciruit malfunction (upstream no)
results: replaced sensor and same results.

P1652-electric cooling fan relay control circuit...results:
relaced the 5 pin relay, both fans spin slowly when before
they didn't work but does not spin fast like before as engine heats up.

P1676-evaporative emission control system purge valve solenoid control circuit...results: at a lost

I could do just about any repair but I don't have the schematics (looked a Haynes but wrong info) and the guidance
such as where to look at and this is where you come into play in the hopes, sir, that thru your understanding and
wisdom you could lay a path to which I can follow.

I'll repeat, all that I said above literally started simutaneously for unknown reason and no forewarnings

Answer
Hi
Here is a bulletin from GM that MAY aid in diagnosis...

Condition
Some customers may comment on one or more of the following conditions:

   •  Engine is hard to start

   •  Engine will not start

   •  Engine starts then stalls

   •  Fuel gauge is inoperative or fluctuates

   •  Service Engine Soon/Check Engine light is illuminated

   •  ABS Warning Light is illuminated

   •  TCS Warning Light is illuminated

   •  TCS activation

   •  Service Traction System message displayed

   •  All-Wheel Drive Disable message displayed

These conditions may be intermittent. Upon investigation, the technician may find various DTCs set.

Cause
This condition may be due to water leaking into the interior of the vehicle, and/or spread terminals, at connector C305 that is located on the floor to the rear of the driver's seat. This connector is not sealed from the inside of the vehicle and water may enter the connector causing the terminals to become corroded. Also, the female terminals of the connector may have become spread apart causing an intermittent poor connection.

Correction
Important:  

  •  Inspect the terminals at connector C305 for corrosion or spreading before replacing the fuel module or resistor card kit. Terminals can be accessed from underneath the vehicle.

  •  Do not attempt to repair any spread female terminals as this will result in a return repair. The female terminal must be replaced.

  •  If the terminals show signs of corrosion, determine the source of the water leak first and repair the water leak before repairing the terminals in connector C305. Refer to Corporate Service Bulletin Number 01-01-38-009A to determine a potential source for water in the vehicle interior.


Repair any corroded and/or spread female terminals in connector C305. Refer to Repairing Connector Terminals in the Wiring Systems sub-section of the appropriate service information.

I Hope this helps.
IF I can help please follow post back.
Good luck
Pawl