The system detected a leak in the evaporative emission system, code P0455 the car is a 2004 Audi A4 Quattro conv 6cyl, 3l.

Location

https://www.google.com/search?q=2006+gmc+canyon+canister+purge+valve+location

The Codes

P0455 GMC Code - Evaporative Emission Control System ...

https://www.engine-codes.com > p0455_gmc
P0455 GMC Code - Evaporative Emission Control System Leak Detected Gross Leak · Possible Causes · How To Fix · Tech Notes ? · Cost to Diagnose · Meaning.

P0442 GMC Code Evaporative Emission Control System Leak ...

https://www.autocodes.com > p0442_gmc
Aug 17, 2017 - The P0442 code means that the control module has detected a small leak in the Evaporative Emission (EVAP). Loose fuel tank filler cap is the ...

Assuming the codes started with the letter P, the codes are listed below.
There is a problem with the system that controls engine emission levels. Get it checked by a good mechanic.
P0135 - O2 Sensor Heater Circuit Bank 1 Sensor 1. P0442 - Evaporative Emission System Leak Detected (small leak).
P0455 - Evaporative Emission System Leak Detected (large leak)

Evaporative Emission Control System Leak Detected Gross Leak

P0455 Ford Evaporative Emission Control System Leak Detected Gross Leak

P0455: Evaporative Emission Control System Leak Detected Gross Leak 1
P0455 Evaporative Emission Control System Leak Detected Gross Leak

P0141: O2 Sensor Heater Circuit Malfunction Bank 1 Sensor 2
P0141 O2 Sensor Heater Circuit Malfunction Bank 1 Sensor 2

Your best bet take it to a qualified repair shop . It takes special tool's to diagnose evaporative emission system's .
DTC P0411 : Secondary Air Injection (AIR) System Incorrect Air Flow Detected
DTC P0449: Evaporative Emission (EVAP) Vent Solenoid Control Circuit
DTC P0455: Evaporative Emission (EVAP) System Large Leak

P0305....Cylinder 5 Misfire Detected

P0442....Evaporative Emission Control System Leak Detected (small leak)

P0455....Evaporative Emission Control System Leak Detected (gross leak)

P0446 Evaporative Emission System Vent Control Circuit.
The following are descriptions of all Evaporative possible codes:

P0441 Evaporative Emission System Incorrect Purge Flow
P0442 Evaporative Emission System Leak Detected (small leak)
P0443 Evaporative Emission System Purge Control Valve Circuit
P0444 Evaporative Emission System Purge Control Valve Circuit Open
P0445 Evaporative Emission System Purge Control Valve Circuit Shorted
P0446 Evaporative Emission System Vent Control Circuit
P0447 Evaporative Emission System Vent Control Circuit Open
P0448 Evaporative Emission System Vent Control Circuit Shorted
P0449 Evaporative Emission System Vent Valve/Solenoid Circuit
P0450 Evaporative Emission System Pressure Sensor/Switch
P0451 Evaporative Emission System Pressure Sensor/Switch Range/Performance
P0452 Evaporative Emission System Pressure Sensor/Switch Low
P0453 Evaporative Emission System Pressure Sensor/Switch High
P0454 Evaporative Emission System Pressure Sensor/Switch Intermittent
P0455 Evaporative Emission System Leak Detected (large leak)
P0456 Evaporative Emission System Leak Detected (very small leak)
P0457 Evaporative Emission System Leak Detected (fuel cap loose/off)
P0458 Evaporative Emission System Purge Control Valve Circuit Low
P0459 Evaporative Emission System Purge Control Valve Circuit High
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At least the cap isn't loose for the gas tank.

I would clear the code with an OBD-II Scanner 'erase code' button, and see how long it takes for it to come back.

p168= The battery has been disconnected within the last 50 starts

p0442=Evaporative Emission System Leak Detected (small leak)

p0455=Evaporative Emission System Leak Detected (large leak)

P0441 Evaporative Emission Control System Incorrect Purge Flow
P0446 Evaporative Emission Control System Vent Control Circuit Malfunction
P0455 Evaporative Emission Control System Leak Detected (Gross Leak)
http://www.toyotanation.com/forum/showthread.php?t=128923

P0411 Secondary Air Injection System Incorrect Flow Detected and P0455 Evaporative Emission Control System Leak Detected (Large Leak). These 2 particular codes are sometimes inter-related.

With a p0455, the most common repair is to:

• Remove and reinstall the gas cap, clear the codes, and drive for a day and see if the codes come back.
• Otherwise, replace the gas cap, and/or
• Inspect the EVAP system for cuts/holes in tubes/hoses (you may hear a vacuum noise or smell fuel), repair if necessary

Let me know if you have anymore questions!

Sincerely,

JC