Cadillac DeVille P0496 OBDII Code Diagnosis

This is one of the most commonly encountered trouble codes for the Cadillac DeVille The P0496 Code. This is the code number for the number given to you by an OBDII scanner when you plug in your DeVille.

Below, you’ll find the most common symptoms and ways to diagnose the P0496 in your Cadillac DeVille. You are very welcome!

Cadillac DeVille P0496 Symptoms

Below are the top symptoms of P0496.

• Erratic Idle– P0496 code in the Cadillac DeVille will often be accompanied by an erratic idle. To find the ideal idle speed, your engine may increase and decrease in revs. This is often what happens right after you purchase gas. The gas station might also not be able to start it.
• Fuel Smell– There may be a noticeable fuel smell right after filling up.
• Coming Soon: Service Engine– More often than not, the only symptom of P0496 will be the OBDII trouble code itself.

If you’re old enough to have driven a carbureted vehicle the old stomp the gas and crank the engine method does actually help start the vehicle. It is because the mixture of air and fuel has been contaminated.
Similar: P0420 Cadillac DeVille

Cadillac DeVille P0496 Meaning

The universal OBDII code P0496 can be used to diagnose trouble codes. The code can be used regardless of the make and model of your vehicle. Technically, the code stands for:

The EVAP system collects fuel vapor from your fuel tank, and then sends it to the intake of the engine to ignite the combustion process.

The Cadillac DeVille computer will emit the OBDII P0496 code if it detects the EVAP system purging in an unintentional manner.

Cadillac DeVille P0496 Causes

The Cadillac DeVille's P0496 code can be caused by many factors. The most frequent problems that cause this code are listed below.

• Vapor Purge Valve– The most common culprit with the P0496 trouble code and the Cadillac DeVille is going to be the vapor canister purge valve. When it goes bad, it typically causes issues with the vehicle’s idle speed. This happens especially after you have fueled the car up. It’s really easy to replace. There are some clips you will need to identify and then remove. Below is an excellent YouTube video that explains how to diagnose the problem.
• PCM– It is possible that the engines computer system itself has gone bad and is registering a P0496 when it shouldn’t be. You should not start there.
• The wiring– It is possible for shorts in the wiring harness leading to the Vapor Canister Purge Valve has gone bad. This is a good article. Here’s a good article on Diagnostics of a car's short.
• Fuel Cap– A bad fuel cap can cause the P0496 code to be thrown for sure. Often, you’ll get a message informing you that the fuel cap is off even when it is on. It may be worth it to get that message and a P0496 for your Cadillac DeVille to have the fuel cap replaced and checked to see if it disappears.
• Oil Tank Pressure Sensor– If the fuel tank pressure sensor has gone bad, it can cause all sorts of problems, including the P0496 code.

Here’s a good video on it:

An engine mechanic will perform a smoke testing to pinpoint the exact source. If you have a hard time figuring it out, it’s pretty easy to do the test.

Conclusion

We wish you all the best in diagnosing and fixing your DeVille. This should help. Please feel free to add anything below.