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code p0446 and speedo calibration question

roy67ss

By roy67ss
in Ask A GM Technician

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roy67ss Enthusiast

roy67ss

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Hi GM Tech, I'm back with a couple of questions.

 

1. I bought the kit to recalibrate the 88-91 truck speedometers. I plugged the connector in and touched the red(+) and black(-) wires to the battery as the instructions say. It did not seem like anything happened which is verified by no change in the speedometer reading. Is there supposed to be some action like a spark or pop or smoke or something to suggest that something was fried? I tried it on both the moony and the tach cluster with no difference.

 

2. My 99 4x4 Silverado NBS has recently lit up the ses light and the code I got was P0446. My Mitchell repair shows a TSB related to plugged venting of the evap canister as a possible for trucks used like I do - lots of mud and gravel roads. I suspect that this will likely be what is causing the fault. Is this a servicable venting system or will I likely be needing to get the revised assembly as mentioned in the TSB 02-06-04-037 dated June 2002 ?

PS. I have also noticed that it does not take fuel as fast as it used to and often need to hand feed it very slowly because it keeps kicking the nossle off even at the first notch.

 

Thanks, Roy

GM-Tech Senior Enthusiast

GM-Tech

Posted
Posted

1. I don't recall there being a noticeable snap or pop when the fuses blew but it has been quite a few years. They're just tiny little fuses. Definitely no smoke. Are you sure there's no change? It's not like you're going to have a 30 mph difference between calibrations.

 

2. I'd put in the revised vent valve. LOTS of problems with those and yeah, if it can't vent it would probably contribute to the gas pump kicking off due to pressure build up in the tank. In severe cases, such as trucks used in farming applications, they suggest running a hose from the vent valve all the way to the air cleaner housing so it can only get filtered air in the valve. You might not have to go that far.

roy67ss Enthusiast

roy67ss

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Thank for the advise again,

1. I expected some sort of reaction from what I read here. There should be a significant change because the cluster came out of a 2wd with 3.42 gears and 15" tires. The truck its going into has 4.10 gears and 265 16" tires. The speedo reads about 45mph when going about 60mph, which is still the same as before I did the burn thing.

The harness I got for connecting to the cluster has 7 red wires connected together and 1 black. Does that sound right? It makes sense from what I see on the printed circuit board.

 

2. Do you know offhand what the part # is for the vent assembly I should replace?

 

Thanks, Roy

GM-Tech Senior Enthusiast

GM-Tech

Posted
Posted
The harness I got for connecting to the cluster has 7 red wires connected together and 1 black. Does that sound right?

 

Honestly, I don't remember. I used to have one of those around here somewhere, but I haven't seen it in a few years. Sounds right but I couldn't guarantee it. Did you put in the new clip with the proper pins broken off?

 

As for the vent valve... I'm sorry, I don't know part numbers. The bulletin you mentioned should have a part # in it I believe.

roy67ss Enthusiast

roy67ss

Posted
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Did you put in the new clip with the proper pins broken off?

 

Yes, I broke off the ones suggested on the sheet.

I'll do some more experimenting on the weekend.

If the burn worked and I didn't put the clip in, would the speedo work at all? If it wouldn't then, I would know that the burn had worked.

 

The bulletin you mentioned should have a part # in it I believe.

 

The buletin info I was reading just described the symtoms and cure, but no part #'s. Probably a shortened version for the Mitchell program.

 

Thanks, Roy

GM-Tech Senior Enthusiast

GM-Tech

Posted
Posted

Here's the full TSB you mentioned, including the part number...

 

 

DTC P0446 (Restricted/Blocked EVAP Vent Path) Set, Service Engine Soon (SES) Lamp Illuminated (Replace Hose/Evaporative Emission (EVAP) Canister Vent Asm) #02-06-04-037A - (Feb 2, 2005)

 

1999-2003 Chevrolet Silverado Models

 

1999-2003 GMC Sierra Models

 

This bulletin is being revised to add model years. Please discard Corporate Bulletin Number 02-06-04-037 (Section 06 -- Engine/Propulsion System).

 

Condition

Some customers whose vehicles are operated in dusty type environments, such as farming or mining off-road type applications, may comment about the illumination of the instrument panel SES light, with a DTC of P0446 (Restricted/Blocked EVAP Vent Path) being set.

 

Cause

Dirt and dust intrusion into the EVAP canister vent hose assembly, resulting in restricted air flow, may cause this condition.

 

Correction

After following the Service Manual diagnostic P0446 and determining that the EVAP canister vent valve is the cause of the SES light, replace the existing EVAP canister vent hose assembly with a new assembly, P/N 15086429. This new assembly has an enhanced filtering capability and a filter element that can be easily removed and cleaned. To ensure correct installation, follow the procedure below.

 

Raise the vehicle. Suitably support the vehicle.

Disconnect the EVAP canister vent valve electrical connector.

Disconnect the vent valve pipe at the EVAP canister.

Remove and retain the EVAP canister vent valve bracket mounting bolt.

Disengage, from the underbody, the two vent valve pipe clips securing the pipe to the underbody.

Remove and discard the complete EVAP canister vent hose assembly.

Position and secure the new assembly to the underbody using the existing hole and mounting bolt.

 

Tighten

Tighten the bracket mounting bolt to 12 N·m (106 lb in).

 

Install the two vent valve pipe clips into the existing underbody holes.

Connect the vent valve pipe to the EVAP canister.

Connect the EVAP canister vent valve electrical connector.

Lower the vehicle.

When properly installed, the new EVAP canister vent hose assembly will be positioned outboard of the original installation location. This new location provides clearance for accessing the filter element for cleaning purposes. To access the filter element, disengage the filter cover to valve locking finger by gently lifting the finger upward while simultaneously rotating the filter body clockwise. After approximately 45 degrees of rotation, the filter can be disengaged from the valve by gently pulling outward. The filter cover can then be removed and the filter element and body can be washed with soap and water. Prior to reinstalling, ensure that the body and filter element are dry.

 

Parts Information

Part Number

Description

 

15086429

Hose Asm-Evap Emis Cnstr Vent

 

 

Parts are currently available from GMSPO.

 

Warranty Information

For vehicles repaired under warranty, use:

 

Labor Operation

Description

Labor Time

 

L0260

Hose, EVAP Emission Canister Vent Valve Asm - Replace

0.4 hr

 

 

 

 

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.

WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION

 

 

© Copyright General Motors Corporation. All Rights Reserved.

roy67ss Enthusiast

roy67ss

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I checked it out at the dealer, wow, the d**n thing is worth $410 list and $328 for my price. I'm going to check it out tomorro and see if I can't figure out some way to use the existing setup with cleaning and better filtering location or something. It has lasted 5+ years and 220,000km now so, maybe I can get some more out of it with a little TLC.

 

 

Thanks again, and I'm sure I'll be picking your brain again, Roy.

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