2017 1.8 NA Code P0449

[mrfixit87]

2017 Sonic 1.8 NA - code P0449 Evap vent circuit malfunction. Replaced the vent solenoid (old one tested 23 ohms upon removal, but replaced anyway because I had already bought a new one and the gas tank was down). Code came back as expected given that the old one wasn’t open circuit. Evap vent solenoid fuse is good. Didn’t check for 12v at evap vent electrical connector as with the fuel tank down I didn’t want to be working on live electricals.

There are 4 codes relating to the evap vent: P0446 (malfunction), P0447 (open), P0448 (shorted), and P0449 (malfunction).

What is the difference between P0446 and P0449? Most online references say that usually replacing the evap vent solenoid fixes P0449 as it’s usually the issue. Shouldn’t an open solenoid could throw a P0447 instead? Seems that P0446 and P0449 are results of function tests that the ecm runs or no? Does anyone know the details of the test that the ecm does that results in the P0449 code as opposed to P0446?

The code is set as a pending code within several seconds from key on after being cleared whether the engine is started or not so it don’t seem to be the result of some lengthy test. The MIL light comes on at the next startup.

Does anyone know what terminal number on the ecm to check for B+ from this solenoid?

A circuit diagram for the 2017 1.8 NA Evap vent circuit would be wonderful!

Thanks!

 

[JTee2017]

Could the malfunction code possibly be set because of a loose gas cap or damage gasket on the gas cap?

Plus . . 2017 and an evap issue . .. still covered under warranty.

 

[mrfixit87]

P0449

The code sets (as pending with MIL off) within seconds of key on with engine on or off. Therefore I think it’s electrical and not performance based like a leak or damaged gas cap (I’ve checked the cap and seals however).

The car already has 48000 miles and as I am let to believe only the vent valve (which I’ve already replaced and know is good) and the ECM are covered under warranty. If there was some way to determine if there is voltage at the ECM plug then I would be confident that it’s an ECM fault and I’d get the dealer to replace under emissions warranty.

If someone knows the pin number on the ECM plug that would be very helpful. A wiring diagram of this circuit would be even better!

 

[92dakota]

it should still be warranty regardless as its emission related, usually longer coverage. but after reading cruze forums, they might not as its considered part of power train.. argh.. go GM.. lol

can be as mentioned tho, Gas Cap, Evap hose leak, Vapor Canister Purge Valve, fuel filler neck, sending unit leak, or electrical chaffing/damaged wire..

 

[dannyg]

If it was me I think I would head over to the dealer to see if it’s a free warranty repair. Walk in there assuming it is! If not ask them for an estimate then decide.

 

[mrfixit87]

Wiring issue

I don’t think it’s the ECM. I found a reference saying that the control line to the ECM on pin 56 of X1 of the ECM connector. Testing that pin there is roughly 1 volt on this pin on the connector until I pull the vent solenoid fuse and then it drops to 0 volts. Therefore I think it’s a problem with wiring or one of the connectors between the ECM and the Evap vent solenoid. One should see V batt on that pin with a DMM and the connector off of the ECM if the vent solenoid is good (new and checked while putting it in) and the wiring/connectors are good. Only the ECM and vent solenoid are covered under warranty AFAIK. Now does anyone know where the connectors between the ECM and Evap vent solenoid are?

 

[mrfixit87]

P0449

Found the connector (X350 is the connector number), its in the passenger rear wheel well behind the splash guard. I see 12V on pin E (red & light blue) as I would expect on the body wiring harness side. On the fuel tank side it reads open circuit between pins D (white wire) and pin E (red & light blue). A good solenoid and wiring would be about 10-30 ohms. Since I know that the solenoid is good it appears now to be a break in the gas tank portion of the wiring harness (most likely at of very near the evap vent solenoid connector). This weekend I will drop the tank, again, and will know for sure.

 

[mrfixit87]

p0449

The problem was a broken wire in the harness between X350 in the passenger wheel well and the solenoid connector. The white (control) wire had corroded through about a foot down the harness from connector X350.