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Ask GM Tech (Cam) Your Own Question
GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 29519
Experience:  GM Grand Master Technician 2007. 14 years experience.
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CHEVY COLORADO: CYL..THE VENT SOLENOID..FUEL PRESSURE..PRESSURE SENSOR

Customer Question

05 CHEVY COLORADO 5 CYL 3.5 LITRE ENGINE 2X4. I HAVE P0446 CODE DESPITE REPLACING THE VENT SOLENOID AND FUEL PRESSURE SENSOR INSIDE THE TANK. FUEL TANK PRESSURE READS AT -7.2 H2O. WHAT DO I DO?
Submitted: 7 years ago.
Category: Chevy
Expert:  GM Tech (Cam) replied 7 years ago.

Greetings and Welcome to Just answer.

Do you drive lots of gravel?

 

Customer: replied 7 years ago.

NO

Expert:  GM Tech (Cam) replied 7 years ago.

This code often sets because the vent does not open. I suggest you check that the system is breathing properly. A plugged EVAP canister will cause this.

 

 

Let me ask you, does it take fuel slowly

 

Customer: replied 7 years ago.
NOT THAT I HAVE NOTICED ANY SLOWER FROM MY OTHER CARS
Expert:  GM Tech (Cam) replied 7 years ago.

OK, . You need to check the canister for being plugged, and it that is ok, then you need to have the system smoke tested.

 

Customer: replied 7 years ago.
IT IS PLUGGED........WHATS A SMOKE TEST
Expert:  GM Tech (Cam) replied 7 years ago.

If it is plugged, then replace it.

A smoke test is what we use to check for leaks and flow by injecting nitrogen smoke to see leaks and flow.

Customer: replied 7 years ago.
WHAT I MEANT BY PLUGGED IS THAT VENT SOLENOID TUBE IS PLUGGED IN TO THE CANISTER...............DO YOU MEAN TO SAY CLOGED THEN I DONT KNOW.
Expert:  GM Tech (Cam) replied 7 years ago.

Yes clogged.

 

Customer: replied 7 years ago.

HOW CAN ONE TELL WHETHER THE CANISTER IS CLOGGED

 

Expert:  GM Tech (Cam) replied 7 years ago.

A smoke test. The system is not letting air through the vent valve to purge the air out of the canister and it sets that code.

 

Customer: replied 7 years ago.

ONE MORE THING: THE CATALYST ON THE TRUCK WOULD NOT GET READY EVEN AFTER DRIVING 1500 MILES. IS THERE A RELATIONSHIP TO THE EVAP PROBLEM.

 

GM DEALER HAS FLASHED THE PCM WITH THE MOST UPDATED PRGRAM 3 WEEKS AGO.

 

Expert:  GM Tech (Cam) replied 7 years ago.

Yes, there likely is.

 

Customer: replied 7 years ago.
WHY WOULD THE CATALYST PASS OR FAIL AFTER DRIVING THROUGH SO MANY DRIVE CYCLES
Expert:  GM Tech (Cam) replied 7 years ago.
The catalyst can fail if the system does not see the proper oxygen sensor readings. Is there a code for the catalyst?
Customer: replied 7 years ago.
THERE IS NO CODE FOR THE CATALYST.. ONLE CODE THAT COMES UP IS P0446. ALL O2'S ARE PASSING YET CATALYST COMES OUT AS " NOT READY" .
Expert:  GM Tech (Cam) replied 7 years ago.

OK, if the evap is not ready, and a code is set such as the P0446, then it will not pass.

 

Customer: replied 7 years ago.
CATALYST IS NEITHER FAILING NOR PASSING!
Expert:  GM Tech (Cam) replied 7 years ago.

It will not fully run if there is a fault in the EVAP system.

 

Customer: replied 7 years ago.
AS I AM A USED CAR DEALER SO YOU KNOW I GO THROUGH THESE PROBLEMS EXTENSIVELY.....I AM WONDERING WHY 100S OF OTHER CARS WITH PO446 NEVER KEPT THE CATALYST FROM PASSING OR FAILING.
Expert:  GM Tech (Cam) replied 7 years ago.

IT depends on the software and PCM. These are a bit of a different beast. I would repair the P0446 and retest.