Can Evap sensor be rewired? [Archive] - GrandAmGT.com Forum

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realestdriver
12-31-2011, 03:20 PM
I got a service engine light for the evap sensor circuit, I replaced the sensor but nothing. When I wash under the hood, it will start working for a little while then light comes back on. I'm thinking about trying to rewire the sensor. I have a pcm pinout, but don't know where the ground goes. Is this something worth trying? Where should my ground be going or is it not really a ground?

I really need to get this fixed because it screws with my tunes and I lost some mpg over this too.

AaronGTR
01-01-2012, 11:34 AM
I got a service engine light for the evap sensor circuit, I replaced the sensor but nothing. When I wash under the hood, it will start working for a little while then light comes back on. I'm thinking about trying to rewire the sensor. I have a pcm pinout, but don't know where the ground goes. Is this something worth trying? Where should my ground be going or is it not really a ground?

I really need to get this fixed because it screws with my tunes and I lost some mpg over this too.



There is no EVAP sensor under the hood. The thing under the hood is a solenoid that opens the EVAP line from the charcoal canister and the fuel tank. It opens an allows vacuum from the engine to purge fuel vapors from the tank to be burned. When it opens it places a vacuum on the fuel tank, then it closes and the tank is supposed to hold a vacuum for a certain amount of time before the solenoid opens again. There is a pressure sensor in the fuel tank (in the unit with the pump and the fuel level sensor I believe) that monitors the vacuum.

If you are getting EVAP codes, it's most likely because of a leak in the system somewhere, or possibly a problem with the wiring to one of the components.

lone_wolf025
01-01-2012, 09:47 PM
There is no EVAP sensor under the hood. The thing under the hood is a solenoid that opens the EVAP line from the charcoal canister and the fuel tank. It opens an allows vacuum from the engine to purge fuel vapors from the tank to be burned. When it opens it places a vacuum on the fuel tank, then it closes and the tank is supposed to hold a vacuum for a certain amount of time before the solenoid opens again. There is a pressure sensor in the fuel tank (in the unit with the pump and the fuel level sensor I believe) that monitors the vacuum.

If you are getting EVAP codes, it's most likely because of a leak in the system somewhere, or possibly a problem with the wiring to one of the components.

Aaron nailed it on the head.

Most common source of a leak is often gas cap going bad or not put on until it clicks. Other possibility is the charcoal canister is saturated with fuel from having too many top offs at the gas station or bad solenoid. Cheapest easiest part to replace is the gas cap.

realestdriver
01-01-2012, 11:14 PM
Why does every time Aaron replies to a post it seems like he is pasting out of an automotive dictionary lol. I forgot about the pressure sensor on the fuel pump assembly, I was thinking the solenoid did the pressure checks. I had a high and low input trouble code for the evaporative emission control system pressure sensor. Definitely going to check that sensor first.

AaronGTR
01-01-2012, 11:34 PM
eh, I've just read a lot of diagnostics info from the manual. :)