PO446 Diagnostic Scan Tool

[Not2oldyet??]

2005 GMC Sierra 1500 WT with a 4.8 L engine 215 k.

My Blue Driver Scan tool reads PO466. It recommended replacing the canister vent valve. Easy enough and inexpensive, so I did.

Cleared the code but it returned. Watched several You Tube videos on the subject. I would replace the fuel pressure sensor next, but that's too much work without confirmation it has failed.

What do you recommend to buy (inexpensive) Scan tool to do the emission system diagnosis ?? I suspect it would be less than what the Auto Shop would charge.

- thanks, Kevin.

 

[Mooseman]

Likely don't need it. It's usually a fairly simple code to fix.

A code P0446 could mean one or more of the following has happened:
Faulty vent valve (which you replaced)
Open, short or excessive resistance on Vent valve control circuit (likely)
Blockage of vent valve (possible)
Bad PCM (unlikely)

You should do a continuity check of each wire from the PCM connector to the purge valve connector

 

[Not2oldyet??]

I WILL check the continuity on that circuit.

- thanks.

 

[mrrsm]

If you are interested... In lieu of getting any other perhaps more sophisticated Scan Tool... what you REALLY could use would be some Directed Component Diagnostic Procedures laid out for you. I have entered your particular 2005 GMC Sierra 4.8L Truck into my Vantage Pro and it has produced around 100 Screen Images covering the Evap and Fuel System Component Diagnostics.

If you think this information will help you... Let me know...and I'll take a few minutes to Crop, Re-Size and Post them here as Five Consecutive Batches of 20 Images per Posting. They include Easy to Understand Graphical and Textual information such as:

(1) Component Functionality.
(2) Component Location and Access (and which Diagnostic Tool to use).
(3) Component Connector and Wire Color with Pin-Outs.
(4) DMM Voltage and Resistance Testing Probe Locations.
(5) What the "Nominal" Ranges for each Component should be.

After taking the time to post up such images in groups like these on another, recent situation for another Member who was simply, "NOT Interested" ...I have since learned my lesson to ASK First. :>)


"How Sharper than a Serpent's Tooth it is...to have an Ungrateful Child... " from Shakespeare's "King Lear"

EDIT: All Set if you ever need these..., and much more interesting and involved than one might imagine.

 

[Not2oldyet??]

Let me check continuity on the purge valve wiring, per Mooseman, first. Simple test.

Very generous offer. I will let you know.

- thanks.

 

[TJBaker57]

FWIW... here is the diagnostic for the P0446

P0446 — 2005 GMC Truck Sierra 1500 4WD V8-4.8L VIN V Service Manual | Operation CHARM

Detailed repair manual for the 2005 GMC Truck Sierra 1500 4WD V8-4.8L VIN V.

charm.li

 

[Mooseman]

That is different than the code's description I found so I would follow what @TJBaker57 posted. Unfortunately it does require the use of an advanced scan tool.

Not a bad idea to check the circuits regardless.

 

[TJBaker57]

Unfortunately it does require the use of an advanced scan tool.

Sometimes I think the diagnostic description is good to help one understand the issue better.

Then perhaps you can devise a method to accomplish the goal without having the fancy scantool.

I have once or twice used a small hand pump to pull some vacuum on an EVAP system for a test. I overshot the mark once and heard the tank 'pop' in a bit !! Too much vacuum !!

 

[AmpOverload]

My Blue Driver Scan tool reads PO466. It recommended replacing the canister vent valve.

Your thread title says P0446 but your 1st post says P0466. Two very different things:

P0446 (ISO/SAE-defined) --> Evaporative Emission Control System Vent Control Circuit
P0466 (ISO/SAE-defined) --> Purge Flow Sensor Circuit Range/Performance

Just to be perfectly clear, which code did your scanner report? Any chance you're chasing the wrong gremlin?

P.S. That 2nd character in the code is a zero (0), not an 'oh' (O).

 

[TJBaker57]

Your thread title says P0446 but your 1st post says P0466. Two very different things:

I don't think I have ever seen a P0466 supported on the GMT360/370 platform.



[naturally I don't expect this screenshot to mean much to all but a few of us ]

 

[AmpOverload]

I don't think I have ever seen a P0466 supported on the GMT360/370 platform.

Excellent point, as usual!

For those who don't "speak OBD2", TJ's datastream shows that PIDs DTCs P0442 and P0446 are supported but P0466 is not ("Request out of range"), for whatever GM vehicle that test was run on.

I've been assuming that the OP really means P0446 (given that he got advice somewhere [presumably directly from the app] suggesting a vent valve replacement), but thought that clarification was in order. (OK, I'm a bit of a stickler for details, I admit it! )

As a side note, as general advice to all who read OBD2 trouble codes, anytime the code description mentions "circuit", it's wise to check the wiring before replacing any part(s), much like @Mooseman already suggested.

EDIT: Oops! I meant DTCs, not PIDs!

 

[AmpOverload]

What do you recommend to buy (inexpensive) Scan tool to do the emission system diagnosis ??

I just remembered that I didn't really answer the OP's question. Don't you just hate it when people do that?

The problem is that to do EVAP system diagnosis, you really need to be able to control both the purge valve and the vent valve. You can sometimes get away with not being able to control the purge valve because it should be closed with the engine off. But the vent valve will be open. So, unless you (A) send the proper voltage to the valve's solenoid manually or (B) have a capable scantool to do that via a PCM command, the open vent valve will stymie most diagnostic efforts!

The other problem is that the commands to control the valves are not standardized -- they're manufacturer-specific. So any scantool that has the requisite database of manufacturer-specific control commands is going to be expensive (because auto manufacturers charge exorbitant amounts for what should be provided cheaply or even free).

So it's hard to recommend a scantool that both (A) provides the necessary control and (B) is inexpensive.

The cheapest option I know of would be running Tech2Win on a VXDIAG VCX Nano, but even that "solution" is fraught with much frustration that can will drive ordinary folks mad! (I speak from experience here!)

I wish I had better advice, but that's the reality in the automotive world.

 

[Not2oldyet??]

My wife had a dream about water and excrement (good luck ??)
Now I have to take her on a Casino junket for a few days.
Will continue the diagnosis on the weekend.

- thanks