I know this has been brought up before, but I can't seem to find an answer.

We just changed the clutch on my son's 2008 SS 5-speed. Of course, we disconnected the battery first.

It's due for inspection by the end of the month and there is a problem.

The catalyst test and the EVAP are not ready. We drove the car for two days for over 160 miles and still not ready. I only need one of the two to be ready because the SS is over 10yrs old one monitor can be not ready and still pass.

There is a problem with the EVAP, so I am topping off the tank to keep EVAP test from running (and failing).

There is a code P0451 pending (Fuel tank pressure sensor performance), but I don't think will set the MIL unless the EVAP test runs, which is why I am inhibiting the test by keeping the tank over 85% full (as per manual).

My question is: will the pending code (P0451) stop the catalyst test from running? Or do I need to drive it even more?

I'm pretty sure I have done this before (on one of the other cars) and the inspection passed with only EVAP test not ready.

To add more variables, it has a ZZP PCM that has been tuned by ZZP. (along with 3-bar sensors). I still have the original PCM, so I could try that, but I don't think a tune would affect the I/M part of the PCM.

Any suggestions? Donbrew?

Steve

 

Hi Steve,
I don't know the answer to you're question, but I think it's safe to say you should fix that P0451 issue before the inspection. The procedure for diagnosing and repairing is straight forward. The service manual states 2 possible issues to set P0451:
P0451 - Part 1
The FTP is greater than 7 in H2O or less than -16 in H2O for more than 4 seconds.

P0451 - Part 2
The fuel tank pressure changed 0.68 kPa compared to a reference value stored at the last cold start.

It states to watch the fuel tank pressure sensor with a scan tool while applying vacuum and while applying pressure, looking for an irregular output.

Hope that helps.
Robert

 

https://www.obd-codes.com/p0451


Was the under hood purge valve disconnected?
Was the canister vent valve under the car damaged?
Any possibility of the wiring loose or a ground wire damaged while you worked in the transmission removal to change the clutch ?
Good reading in the link I posted, you may have read it, already.

 

P0451 inhibits both tests. Conditions for running the EVAP include between 1/2 and 3/4 tank of gas when you park it for the day then it runs overnight. It should run after 7 cold starts.

here are the conditions for P0451:

And a pdf of the entire article.


P0451.pdf

 

Thanks, Donbrew.

I guess I will have to solve the P0451.

The only thing that doesn't seem to match the description of when P0451 gets set is that the fuel level is between 12-88 percent. I filled the tank, and then erased the codes. After driving a couple of miles I pulled over and read the codes. The P0451 was now pending again. Maybe the P0451 test occurs all the time, but only sets the MIL if conditions are met? That would explain why the code is pending but never actually set the MIL since I made sure the tank was always above 90%.

I will do the sensor electrical tests described in your pdf and replace the FTP if necessary. However, since this is a sensor "performance".code and not a "stuck high or low" code, that implies the sensor may be good but one of the other causes (EVAP canister plugged or sensor reference port plugged).

Maybe I will replace the FTP sensor since its not too expensive and then if that doesn't solve it I will take it in to a mechanic with better scan tools that can do some of the tests described din the article.

Steve

It also looks like an

 

Can you blow air through the EVAP purge valve under the hood?
By you description of the pending code and conditions not met, yet, perhaps it’s just one of the computers tasks to continually run tests until it recognizes an anomaly in the algorithm.

 

Hey Robert
What does it mean “FTP is greater than 7 in H2O or less than -16 in H2O for more than 4 seconds”….what is FTP and H20. I have an H2O sensor that is active on my 2007 HHR using “Car Scanner Pro” and Veepak OBD2
squibt

Ahh..Fuel Tank Pressure? But H2O?

 

A 16 inch column of water. A measure of pressure.
I have no clue what you might be seeing as H2O sensor, no such thing on an HHR.

 

Got a private message that apparently H2O is a typo here. I contacted Car Scanner Pro and asked about the H2O sensor reading on my HHR…Hope they get back to me. Seems any sensor not available for my HHR will only display a solid line at 0 on a graph…funny this H20 graph registers….see my post for more info.

Emissions Test OBDII

 

Probably supposed to be HO2 sensor. Heated oxygen sensor. You're not dyslexic, are you?