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1998 gmc sonoma 4 clinder p0440

  • cheryl hartkorn
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30 Sep 2019 20:03 #33948 by cheryl hartkorn
1998 gmc sonoma 4 clinder p0440 was created by cheryl hartkorn
its been forever since i worked on one of these. i thought i had a bad purge valve because i couldnt pull a vacuum on the system according to the scanner. fuel tank pressure sensor stays at 1.5 volts. smoke it no leaks with vent vlave closed. fuel tank pressure sensor stays at 1.5 volts even with smoke machine on system. hear purge click no vacuum coming out of it at idle. find no vacuum from hose that goes on throttle body at idle. its ported vacuum? anyone remember back that far? i even closed vent valve puilled strong vacuum on system from an intake source. so now im thinking i have a stuck fuel tank pressure sensor. sound like thats the issue?

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30 Sep 2019 20:17 #33949 by Tyler
Replied by Tyler on topic 1998 gmc sonoma 4 clinder p0440
Definitely sounds like the sensor is stuck. Should have started reading lower voltage with the smoke machine on the system, especially if you got the flow gauge to show zero. Sensor time!

As for the vacuum source for the purge valve... I have no idea. :lol: Most of these trucks that came into my bay had bigger problems, like blown head gaskets and smoked wheel bearings.

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30 Sep 2019 20:49 #33954 by Cheryl
Replied by Cheryl on topic 1998 gmc sonoma 4 clinder p0440
That’s what I was thinking especially when I stole vacuum from the brake booster and closed the vent valve was expecting to see a huge voltage spike in a very short time. Had to bust out the old antique tech 2 since snap on had no purge and seal option

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01 Oct 2019 17:56 #33965 by Cheryl
Replied by Cheryl on topic 1998 gmc sonoma 4 clinder p0440
Installed new tank pressure sensor now reads according to pressure and vacuum changes. But drove it threw a p0122 tps low code now have to scope that

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01 Oct 2019 18:09 #33967 by Tyler
Replied by Tyler on topic 1998 gmc sonoma 4 clinder p0440
Not that I encourage parts changing, but I might just put a TPS on it. :silly: I chased the same code on an Isuzu Hombre (rebadged Jimmy/Sonoma) for three days before I just gave in and replaced it.

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01 Oct 2019 18:34 #33968 by Cheryl
Replied by Cheryl on topic 1998 gmc sonoma 4 clinder p0440
That’s what I was just going to do on this beater. Just helping out a broke friend

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