Troubleshooting P0452, 2001 Silverado

[Rhymingmechanic]

2001 Silverado 5.3, 111,000 miles, 2WD regular cab short box. Driven in three Michigan winters (road salt, the gift that keeps on giving), otherwise in the South and arid West.

I got an SES light, code P0452, "Evaporative emission control system pressure sensor low input."

No fuel smell, no problems filling the tank, and no difference in how the truck runs.

Here's what I've tried so far:

1. Replaced the gas cap with the original, which I used for 2-3 years before the current locking cap. Cleared code but it came back on the next start.

2. Unplugged and re-plugged the fuel tank pressure sensor connector, mainly to see if I could access the sensor without pulling the bed or tank. Snugged the big filler tube hose clamps at the same time. Cleared code but it came back again.

I also jiggled all of the line connections I could reach and felt the lines for damage. This was basically a blind operation, since the lines are above the fuel tank.

I'm reading and clearing codes with the paid version of Torque on an Android tablet. It has options for EVAP and Fuel Tank Pressue gauges--I activated both, but only the EVAP gauge gets data. EVAP reads between 12 and 19 percent, whatever that means, when I check it.

What other troubleshooting can I do without a "real" scanner? Does the info above suggest an obvious repair?

Thanks in advance for your suggestions.

 

[Ramblejam]

You haven't actually replaced the sensor though, correct?

https://amzn.com/B000NW4OPC

$11 for the OE Part!

 

[Rhymingmechanic]

No, I didn't replace the sensor, but that's probably the first part I would throw at it.

Thanks for the link--that's a lot less than the $35 AC Delco on Rockauto.

 

[Silverado12]

^^^That is the sensor you need to replace. I did mine on my 2012 Silverado (don't know why GM makes the same mistakes over and over again with some of these parts).

 

[Silverado12]

FWIW you don't have to drop the tank or lift the bed off to do this repair as there is enough room to get your hand on top of the fuel tank. You can feel for it and it just pulls out. Unplug the connector first, then pull straight out. If the blue rubber part breaks and comes out in pieces, you can just push the rest into the gas tank. It won't hurt anything. Make sure you get the ACDelco part. I got ripped by the dealer for about 40 bucks.

 

[Silverado12]

Fuel pump pic


Note the location of the sensor on the fuel pump as you will have to feel for it.

 

[Rhymingmechanic]

I felt around up there, and I'm sure I can replace the pressure sensor from underneath. Did that solve the problem on your 2012? (Did you have the P0452 code?)

 

[Silverado12]

Can't remember the code number, but the new sensor solved my issue. This is a common problem with these trucks.

 

[The_Eric]

Yep, most likely a sensor, but here is the troubleshooting process:

: 1. Probe the Dark Green wire at the Powertrain Control Module (PCM) Red connector pin 64, and verify fuel tank pressure readings. Key on with gas cap off it normally is 1.3-1.7 volts.

2. If voltage is outside of specification, then go back to the tank and access the fuel tank pressure sensor. Probe the Dark Green wire again and see if voltage is the same or different.

3. Check the Gray wire to the sensor for 5 volt reference and then check the Black ground wire to the tank pressure sensor, to make sure it is a good ground.

5. If 5 volt reference and ground is OK but voltage on Dark Green is incorrect, then replace the tank pressure sensor.

 

[Merkava_4]

I get that code once or twice a year on my Buick. Changing the sensor didn't help. Wiring is good. I read somewhere online that a PCM reflash is the cure.

 

[Rhymingmechanic]

Originally Posted By: The_Eric
Yep, most likely a sensor, but here is the troubleshooting process:

: 1. Probe the Dark Green wire at the Powertrain Control Module (PCM) Red connector pin 64, and verify fuel tank pressure readings. Key on with gas cap off it normally is 1.3-1.7 volts.

2. If voltage is outside of specification, then go back to the tank and access the fuel tank pressure sensor. Probe the Dark Green wire again and see if voltage is the same or different.

3. Check the Gray wire to the sensor for 5 volt reference and then check the Black ground wire to the tank pressure sensor, to make sure it is a good ground.

5. If 5 volt reference and ground is OK but voltage on Dark Green is incorrect, then replace the tank pressure sensor.


Thanks for the details, Eric.

Do you actually pierce the insulation, or is there a tool that will probe the connector without damage? I'm always hesitant when I read about these electrical tests, because I don't want to introduce corrosion to the wires.

 

[Rhymingmechanic]

Update: Condition Fixed

I ordered a new FTP sensor and got underneath to change it. When I unplugged the connector, here's what I got:





All three wires were broken at the same place. A squirrel or chipmunk must have chewed it. I guess they wanted something besides tomatoes this year.

I put on a new connector from Advance Auto and cleared the code. No Service Engine Soon light since then.