P0452/P0442 Evap Codes

[Rick Norwood]

Here goes my tale of woes. 2000 GMC Jimmy 4.3L 2WD. Approximately 3 years ago, I had a couple of issues with an SES light and an EVAP code (don’t Remember which code). I replaced the gas cap and all was well. Then about two years ago, my fuel gage went on the fritz due to the sending unit in the tank. About 3-4 months ago, My Fuel pump went completely out. I replaced it with an aftermarket pump and filter. The new Fuel pump had a different electrical connector and required the original connector to be cut off and the new one spliced on, But the Tank Sensor connector was the same as OEM. Once the new fuel pump assembly was installed, everything started working again. The Fuel gage works now, as well as the low fuel indicator light. Within the first 100 miles after installing the new fuel pump, the SES light came on showing a P0452 code (I think), which I cleared at AutoZone. Ever since, the SES light comes on every 4-5 weeks and throws a P0442 code. The Truck has supposedly been smoke tested with a scanner attached (to open/close the purge valve) to no avail, and another brand new gas cap was installed but nothing helps. I have checked the rubber hoses and clamps at the tank and can’t find anything wrong.

One question I have is, would the defective sending in the old Fuel Pump Assembly somehow disallow the EVAP test from running for like two years? I think someone told me that very certain and specific conditions must be met before the Test will run again, which could take months to happen.

I have read on the internet that everything from filling your tank too full to bad hoses can cause this code to set. Are these things that difficult to fix? I have an emissions test in July and would like to pass.

Any Help would be appreciated. Special Thanks to Old Master for all of the PM help.

Rick

[s10blazerman4x4]

I can not be of any help but I will be watching this thread as my truck threw the same codes other day and I too had autozone clear them. Nothing seems to be wrong. This may sound crazy but how is your thermostat. I was running rich due to poor thermostat and I think since I changed that this morning it solved my problem because Im now in proper operating temperature. Wish you luck.

[Rick Norwood]

Originally Posted by s10blazerman4x4

I can not be of any help but I will be watching this thread as my truck threw the same codes other day and I too had autozone clear them. Nothing seems to be wrong. This may sound crazy but how is your thermostat. I was running rich due to poor thermostat and I think since I changed that this morning it solved my problem because Im now in proper operating temperature. Wish you luck.

My T-Stat is fine. One thing I have learned with this is that it takes 4-6 weeks for my Jimmy to repeat the test. You almost get a false sense of security that you fixed the problem, them BAM, the light comes on again and it's back to Autozone to clear the code.

I am starting to think the Aftermarket Sensor mounted on the top of the Aftermarket Fuel Pump is either defective or simply not compatible with the GM system.

[s10blazerman4x4]

I agree with you on that false sense of security. Mine takes the same time to kick.

[s10blazerman4x4]

Was wondering if you solved it Rick.

[Rick Norwood]

No, not yet. My SES light comes on approx. every 6-8 weeks and I go get it turned off. However, I have learned a couple of things. I was told that when replacing the fuel pump, you need to lube the big O-Ring that seals the pump to the tank to keep it from twisting when sliding the new fuel pump down into the tank. The other thing is that you should not fill the tank completely full to the very top when refueling. This can cause the system to suck in liquid fuel as opposed to vapors when the Evap test runs.

I have a sneaking suspicion that the guy who did the R&R on my fuel pump didn’t lube the O-Ring or maybe I’ve been bitten by the undersize O-Ring thing again. I did a post about a year ago on my old 93 S-10 Blazer where I used the O-Ring that came in the box with the new Fuel Pump and found out it was .031 too thin (too small in thickness diameter not overall Diameter). We ended up having to buy a gasket from the Dealership. The funny thing is we didn’t throw any codes or leak any fuel with the undersize O-Ring, we just didn’t pass the Fuel tank pressure test at the Emissions Testing Station, but then I’m not sure that 93’s had the Evap test.

[s10blazerman4x4]

Sorry its so late for my reply just now saw this again. At least your is 6-8 weeks, mines every second day. It will go off for a day come back on next day stay on for a week then go off. Im trying to find the vent solenoid/valve but cant find it anywhere.

[jbarsalou]

Is there a way to force an evap test? The scanner keeps saying "not ready" for the readiness test. I've fixed all my emissiom problems (not evap related) and need to go for reinspection. MA requires all I/M readiness tests to be complete for inspection. Since the repair and code clear, I've driven over 400 miles and filled the tank twice. I've even completed the "drive cycle" numerous times which should force all tests to ready in about 20 minutes but it won't work. I haven't had any more codes either. Any ideas?

[old_master]

Does the fuel gauge work correctly? The EVAP monitor will not run if the level sensor is faulty.

Complete steps 2 through 8, this will force the EVAP monitor to run
http://www.obdii.com/drivecycle.html

[jbarsalou]

Thanks for the link Old Master, I have that drive cycle from one of my shop manuals. I've been driving in "drive" so it would slow down faster than in overdrive but it doesn't specify which gear to be in. It looks pretty suspicious going 20mhp on a 55mph road with an expired sticker. I know not to brake but the Helms book didn't mention not to shift though in tests 5 and 8. I was shifting down to 2nd to get the speed down quicker.

My fuel gauge floats around all the time but it does show full when the tank is filled and E when the tank is empty. Between the two it's all over the place. I've replaced it already several times and got used to paying attention to mileage for knowing how much gas I have. I'll try again tomorrow night and let you know how I made out. Thanks again.

[old_master]

The EVAP monitor will only run if the fuel level is indicating between 15% and 85% full. During the test, the ECM checks the fuel level and calculates the amount of "empty space" in the tank. It then activates the EVAP solenoid for a calculated amount of time, then deactivates the solenoid. This applies manifold vacuum to the tank. The ECM then "watches" how long it takes for the vacuum to deteriorate. If it deteriorates too quickly, (indicating a leak), it sets the DTC.

If the fuel gauge "floats around" it means the buffer in the level sensor is faulty or there's a poor connection somewhere, and as a result, the ECM cannot get an accurate reading of the fuel level and the monitor will not run. When performing the drive cycle, leave the transmission in overdrive, don't downshift.

[wayne64]

Originally Posted by old_master

The EVAP monitor will only run if the fuel level is indicating between 15% and 85% full. During the test, the ECM checks the fuel level and calculates the amount of "empty space" in the tank. It then activates the EVAP solenoid for a calculated amount of time, then deactivates the solenoid. This applies manifold vacuum to the tank. The ECM then "watches" how long it takes for the vacuum to deteriorate. If it deteriorates too quickly, (indicating a leak), it sets the DTC.

If the fuel gauge "floats around" it means the buffer in the level sensor is faulty or there's a poor connection somewhere, and as a result, the ECM cannot get an accurate reading of the fuel level and the monitor will not run. When performing the drive cycle, leave the transmission in overdrive, don't downshift.

Thanks much for the OBDII link and our 96 S-10 Blazer has been doing the same stuff since I replaced the fuel pump. The fuel gauge reads good and I must have a leak somewhere. So the big question is how to fool the testing. Always stay almost empty or full after a code clearing? Better yet I know some hard codes can be stopped in earlier (pre-96) Fords by adding resisters or by supplying a correct reference signal voltage to the computer. Any thoughts on doing this? I refuse to pull the pump again

[old_master]

Originally Posted by wayne64

Thanks much for the OBDII link and our 96 S-10 Blazer has been doing the same stuff since I replaced the fuel pump. The fuel gauge reads good and I must have a leak somewhere. So the big question is how to fool the testing. Always stay almost empty or full after a code clearing? Better yet I know some hard codes can be stopped in earlier (pre-96) Fords by adding resisters or by supplying a correct reference signal voltage to the computer. Any thoughts on doing this? I refuse to pull the pump again

If the EVAP code started right after the fuel pump replacement, there's a good chance the O ring for the module is not sealing properly. When replacing the module, always put a coating of vaseline on the O ring, and make sure the hose clamps are tight on the filler neck and vent line.

[wayne64]

Thanks Old_Master, I did my fuel pump change out by
1. taking measurements
2. removing rear seats
3. cutting floor with a body saw
4. changed pump and replaced cut out with pops and body sealer
5. replaced seats

So I never distrubed the filler hoses, BUT I couldn't get the new O-ring to fit so I used the original one. Yes I guess I screwed up, and since the next inspection is in August I will have to address that O-ring before. Unless I can defeat the signal. I'm a combat disabled vet and cutting the floor worked for me, instead of dropping the tank.

[old_master]

Originally Posted by wayne64

Thanks Old_Master, I did my fuel pump change out by
1. taking measurements
2. removing rear seats
3. cutting floor with a body saw
4. changed pump and replaced cut out with pops and body sealer
5. replaced seats

So I never distrubed the filler hoses, BUT I couldn't get the new O-ring to fit so I used the original one. Yes I guess I screwed up, and since the next inspection is in August I will have to address that O-ring before. Unless I can defeat the signal. I'm a combat disabled vet and cutting the floor worked for me, instead of dropping the tank.

I understand, my heart goes out to you! If you clean both of the O ring surfaces, and use vaseline, it will go in very easily, (use the new O ring.)