P0496 Code on a Cadillac: EVAP Flow During Non-Purge (Cadillac Guide)

P0496 on a Cadillac is GM's "EVAP System Flow During Non-Purge." In plain terms, the purge valve is leaking. The engine computer closed it, sealed the EVAP system, and the fuel tank still got pulled into vacuum. This one matters more than most EVAP codes, because a purge valve that won't close lets raw fuel vapor into the engine and can cause rough idle, hesitation or stalling, especially right after a fill-up. GM has paid to fix it on several Cadillacs: special coverages on the purge valve for the 2006 CTS, SRX and STS, the 2015 ATS, CTS, SRX and XTS and the 2019 XTS. There is also a 2019 XT4 bulletin that traces P0496 to air leaks around the turbo engine's purge pump.

What Does P0496 Mean on a Cadillac?

The purge valve, which GM calls the evaporative emission canister purge solenoid valve, sits between the charcoal canister and the intake. When the ECM wants to burn stored fuel vapor, it pulses the valve open and engine vacuum draws vapor in. When the ECM closes it, nothing should flow.

P0496 says something did flow. GM's 2019 table for the 3.6L V6 group (XT5, XTS, ATS, CTS, CT6) puts it this way: the DTC "will determine if the purge solenoid is leaking to engine manifold vacuum." Both the purge and vent valves are closed, and the ECM watches tank vacuum. "The fuel tank vacuum level should not increase. If tank vacuum increases above a threshold, a malfunction is indicated."

For the cross-brand explanation, see our GM P0496 guide.

How the Test Works

• When it runs: on a cold start in the 2019 3.6L table, with the engine off for at least 28,800 seconds (8 hours) beforehand, fuel level between 10% and 90%, startup coolant at 35 °C or below and startup intake air between 4 °C and 35 °C. In practice it runs on the first drive of the morning.
• What fails it: tank vacuum above 2,491 Pa for 5 seconds while the system is sealed. The test time only counts while engine vacuum is at least 10 kPa, because there has to be vacuum on the far side of the valve for a leak to show.
• How the light comes on: Type B, two trips.
• On a 2004 Northstar (DeVille, Seville, Eldorado), the table sets it when tank vacuum exceeds 10 inches of water for 5 seconds before purge time passes 60 seconds. Also Type B.

A leaking purge valve also shows up in the other EVAP tests. With vacuum leaking through constantly, the large-leak and small-leak tests can misread, and the extra vapor skews fuel trim. That's why GM's purge valve coverages list P0442, P0455, P0171 and P0174 next to P0496.

Which Cadillacs Set P0496

This is where Cadillac history gets specific. GM's tables show the switch from older codes:

• Northstar 4.6L (DeVille, Seville, Eldorado): through the 2003 tables, a leaking purge valve set P1441 ("Continuous Open Purge Flow"). P0496 takes over in the 2004 table.
• Escalade: the truck V8 tables used P1441 through 2002 and P0496 from 2003.
• CTS: the 2003 3.2L table already uses P0496, described as a pressure gradient check with the purge valve and canister vent valve closed.
• Catera (1997–2001): the Opel-built 3.0L tables we read list neither P0496 nor P1441.
• Everything since: every 3.6L, 2.8T, 3.0L, 2.0T, 2.7T, 3.0TT and V8 Cadillac group we checked through 2025 uses P0496.

The electric Lyriq and Optiq have no EVAP system. If a scan tool reports P0496 on a pre-2004 Northstar or a pre-2003 Escalade, re-read the code with a GM-capable tool. The car probably stored P1441.

Cadillac Purge Valve Coverages

2006 CTS, SRX and STS: Special Coverage 09205 (March 2010). GM's owner letter covers 2006 CTS, SRX and STS models with the 3.6L V6 and the 2006 CTS with the 2.8L V6, where the purge solenoid valve "may stick open or closed," turning on the service engine soon light. Coverage was 10 years or 120,000 miles. The term has passed for practical purposes, but a dealer VIN check costs nothing.

2015 ATS, CTS, SRX and XTS: Special Coverage 18029 (June 2018). GM found that certain 2015 vehicles "may have an inoperative purge solenoid that could lead to excessive fuel vapors entering the combustion chamber from the fuel tank," which could cause a no-start, idle stall or hesitation. The driver may see a check engine light and hear a ticking noise, "most immediately after filling up the vehicle with gas or while coming to a stop." Dealers inspect for a leak in the solenoid and replace it with valve 12690512 if needed. Coverage is 10 years or 120,000 miles from the in-service date, so most 2015 Cadillacs are now past it. It's still worth a VIN check on a low-mileage car first registered late.

2019 XTS: Special Coverage N222369620 (June 2022). This covers the 2019 XTS with the 3.6L LFX, shared with the 2020 Impala. The purge valve "may not fully close," which can make the engine run rough, hesitate or stall at idle. GM's procedure says the car "may come in with DTCs including any of the following: P0496, P0442, P0455, P0171, or P0174," and the part is again valve 12690512. Coverage is 15 years or 150,000 miles, so it is still active for most 2019 XTS owners.

2013 XTS: purge valve and canister (PI0898, January 2013). This one is about P0455, not P0496. But it is a useful Cadillac lesson. If the purge solenoid is found sticking, GM says to replace both the purge valve (12610560) and the canister (23116138), and to blow out all EVAP lines with compressed air at no more than 5 psi. Otherwise charcoal debris left in the lines can make the code come back. GM also points to overfilling the tank as a cause.

XT4 and the Turbo Purge Pump

The 2.0L turbo LSY (XT4, CT4, CT5, XT5, XT6 and 2019 CT6) and the 2.7L L3B (CT4) use an electric purge pump, because a turbo engine doesn't always have intake vacuum to pull vapor through.

PIP5634, 2019 XT4. GM's preliminary information for the 2019 XT4 2.0L says P0496 "may be caused by a purge system air leak." After normal diagnostics, technicians smoke test the purge side at the purge valve and check, in order: the purge pump body's internal O-ring, the pump-to-tube O-ring, the tube connections, and the joint between the purge valve and its adapter. If the leak is between the valve and the adapter, or past the valve into the adapter, GM says do not separate them and replace them as an assembly.

Purge pump coverages are a different problem. GM has several special coverages for a failing purge pump on these engines: N202324990 (2019–2020 XT4), N232395310 (2020 CT4, CT5, XT5), N242441120 (2021 LSY models, including the XT4, CT4, CT5, XT5 and XT6) and N242484740 (2022–2023 models). They list pump codes such as P1467 and P146B–P146F, not P0496. GM's 23-NA-214 also explains that pump part numbers are interchangeable during a supply shortage. If your XT4 shows P0496 alone, these coverages don't automatically apply. If it shows P146x codes as well, ask the dealer to check them.

Symptoms of P0496

• Check engine light
• Hard starting, rough idle or stalling right after refueling
• Hesitation, or idle speed that wanders as you come to a stop
• A ticking noise from the purge valve area (named in GM's 18029 coverage)
• P0442, P0455, P0171 or P0174 at the same time
• A failed emissions inspection

Causes and How to Confirm Each

How Is P0496 Diagnosed on a Cadillac?

1. Check the VIN for open coverages first. 09205, 18029 and N222369620 cover purge valves on specific Cadillacs, and the dealer does the diagnosis under the program.
2. Read all codes. P0496 with P0171/P0174 or a stall after fueling is the classic purge valve pattern. P1467 or other P146x codes on a turbo point to the purge pump.
3. Check tank pressure with the cap off to confirm the sensor reads near zero.
4. Command the purge valve closed with the engine idling and watch tank vacuum. If it climbs, the valve is passing flow.
5. Bench or vacuum test the valve. It should hold when closed.
6. On a 2.0T or 2.7T, smoke test the purge pump side as PIP5634 describes.
7. If you replace the valve, check for charcoal in the lines and canister, and clean the lines so a new valve isn't held open by debris.
8. Clear the codes and let the cold-start test run. It needs an engine-off soak, so expect to wait for a drive after an overnight stop.

Parts and Cost

GM Documents That Name P0496 or Purge Valves on a Cadillac

Have a dealer check your VIN against current bulletins and campaigns rather than relying on any article, including this one.

What Other P0496 Pages Get Wrong

• "It's just a gas cap." P0496 is the purge valve leaking toward the engine. A cap can't cause flow when the system is sealed.
• Treating it as harmless. GM's own coverages link a leaking purge valve to stalling and no-start after fueling.
• Paying before checking coverage. The 2019 XTS has 15 years or 150,000 miles under N222369620.
• Mixing up purge pump and purge valve problems. The turbo purge pump coverages list P146x codes, not P0496.
• Replacing only the valve after charcoal contamination. GM's XTS bulletin says to clean all the lines, or the problem returns.

Frequently Asked Questions

Is P0496 serious on a Cadillac?

It can be. Many cars only show a light, but GM's own coverages describe stalling, hard starting and hesitation after fill-ups from a purge valve that won't close. Don't let it sit.

Will GM pay for my purge valve?

Possibly. The 2019 XTS is covered for 15 years or 150,000 miles under N222369620. The 2015 ATS, CTS, SRX and XTS (18029) and the 2006 CTS, SRX and STS (09205) had 10-year/120,000-mile coverage that has mostly passed. Have a dealer check your VIN.

Why does my Cadillac stall after I fill up?

Refueling pushes a burst of vapor into the canister. If the purge valve is leaking, that vapor goes straight into the intake at idle and floods the mixture. GM's 18029 coverage describes exactly this.

My XT4 has P0496. Is it the purge pump coverage?

Not necessarily. GM's PIP5634 traces P0496 on the 2019 XT4 to air leaks in the purge system, including the pump's O-rings and the valve-to-adapter joint. The purge pump coverages are for pump failures with P146x codes.

Can I drive with P0496?

Usually, if the car starts and idles normally. If it stalls or struggles after fueling, get it fixed soon.

What's the part number?

GM's 2015 and 2019 Cadillac coverages list purge valve 12690512, but the right valve depends on your VIN. Confirm fitment before ordering.