P0499 Evaporative Emission System Vent Valve Control Circuit High
OBD-II Trouble Code Technical Description
Evaporative Emission System Vent Valve Control Circuit High
What does that mean?
This code is a generic powertrain code. It is considered generic because it applies to all makes and models of vehicles (1996-newer), although specific repair steps may vary depending on the model.
The Powertrain Control Module (PCM) / Engine Management Computer (EMC) / Engine Control Module (ECM) has detected a fault with the circuit that controls the vent for evaporative emission systems vapor.
As fuel sits in the tank it lets out fuel vapor, while driving this vent opens and allows the vapors to be circulated into the engine intake manifold, a charcoal canister or into the atmosphere, depending on the vehicle. This vent valve is apart of the simple, yet complicated evaporative emissions system.
Symptoms
Symptoms of a P0499 DTC will include Malfunction Indicator Lamp (MIL) illumination, you will likely not notice any other symptoms.
Causes
Potential causes may include:
Faulty vent valve Wire/circuit issue PCM/EMC/ECM faultPossible Solutions
Some steps to take to diagnose and repair this trouble code include the following:
Check your fuses, there may be a fuse that powers the vent solenoid.
Check for a rubbed-through or chafed wiring harness. Check both wires to see if they are shorted to each other, to ground or power.
Visually inspect the vent valve for cracks or damage.
Trace the wires to and from the PCM/EMC/ECM and check for continuity continuity using a digital volt ohm meter (DVOM).
If you have access to an advanced level scan tool, actuate the valve while reading power and ground at the connector or by simply using a bulb wired to both terminals, it will light up if power and ground are OK.
Using a DVOM, check the resistance of the vent, in most cases the resistance reading should be low, refer to the manufacturer’s specification or compare it to a new one. Too high or low a value indicates a faulty coil inside the valve, thusly meaning replacement is necessary. This code seems to be prevalent on Dodge, Chrsyler, and Jeep products. In those cases the vent valve was bad. With GM products (specifically pickups), GM has released a new updated valve assembly.
Finally, remove the valve, you may be able to access the pintle inside and it simply could just be sticking from fuel residue. Clean it and retest.
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