1997 K1500 Fuel Tank Pressure Sensor?

[RobertISaar]

from a very condensed point of view:

normally, the PCM allows the engine vacuum that would normally draw fumes from the CCP and allow the tank to vent as necessary. it also controls a solenoid that prevents the tank from venting vacuum. so the solenoid is switched when the engine is creating vacuum, causing a vacuum to exist in the tank. the tank pressure/vacuum sensor is read to determine if there is enough vacuum to consider it a pass. this tests a couple of things at once, mostly CCP and fuel tank integrity.

i might be able to grab a better explanation, but that's essentially how it all works.

[Caleditor]

This is for 1996 and 1997 ONLY!

Evaporative Emission Control System


Purpose
The Evaporative Emission (EVAP) control system limits the fuel vapors from escaping into the atmosphere. The EVAP transfers the fuel vapor from the sealed fuel tank to an activated carbon (charcoal) storage device (EVAP canister). The EVAP canister stores the vapors until the engine is able to use the extra fuel vapor.
When the engine is able to use the extra fuel vapor, the intake air flow purges the fuel vapor from the carbon element, and then the normal combustion process consumes the fuel vapor.
The fuel tank is sealed with a fuel cap that is not normally vented to atmosphere. The fuel tank cap has a safety valve which allows for both pressure and vacuum relief.
Operation
Fuel vapors from the fuel tank purge and flow into the EVAP canister tube labeled Tank and the carbon absorbs the vapors. The canister purges when the engine is able to use extra fuel vapor. A vacuum source is applied to the EVAP canister tube labeled Purge to draw fresh air through the top of the canister. The air mixes with the fuel vapor and the mixture is drawn in the intake manifold to be consumed in the normal combustion process.
While the canister is purging, fresh air is drawn in through the air inlet at the top of the canister. Air flows to the bottom of the canister and forces the vapors out the Purge tube.
The EVAP system in some applications uses an electrically controlled solenoid to cycle the vacuum to the purge canister. The control module cycles the solenoid when the engine coolant temperature is greater than 45°C or the Short Term Fuel Trim counter is less than 122.

A vacuum switch in the purge line detects when the system is purging. The normally closed switch will open when less than 1 inch Hg is present in the purge line.

EVAP Canister Location
The canister is located in the left front fender well.

[Caleditor]

1998 on up use FTP Sensors

Hey Dave I posted the Schematics for you

[dave w]

1998 on up use FTP Sensors

Hey Dave I posted the Schematics for you

Thanks, for posting the wiring diagrams! http://www.gearhead-efi.com/Fuel-Inj...9545#post29545
Seems like I can't find the wiring schematic for the Fuel Tank Pressure Sensor show in post #1.

dave w

[Caleditor]

Thanks, for posting the wiring diagrams! http://www.gearhead-efi.com/Fuel-Inj...9545#post29545
Seems like I can't find the wiring schematic for the Fuel Tank Pressure Sensor show in post #1.

dave w

It was not used in 1997

[Fast355]

It was not used in 1997

I have a 97 Express 1500 and can confirm no FTP sensor in my application and can also confirm with the sensor codes turned off I still get the monitor to show "Ready" status.

[dave w]

It was not used in 1997

Maybe California Emissions for 1997? The vehicle owner lives in Oregon. Very common to find California emission vehicles in Oregon.

dave w

[1project2many]

Dave, have you confirmed 97 Model year vs 97 manufacturing year? Emissions label will provide all needed answers here... "Vehicle conforms to Federal (or Federal and California) emissions standards for 199X model year."

[Caleditor]

Maybe California Emissions for 1997? The vehicle owner lives in Oregon. Very common to find California emission vehicles in Oregon.

dave w

Dave I have a 1997 and I think it has a sensor. I just did a 0411 swap and I think the wires were in place. I was going to look over the weekend and never made it out to the truck. I will look tonight