My turn for a SES light

I'm sure it's just a coincidence... let my wife drive the Riv yesterday as I needed her van to haul a ladder. Anyway, I drove it to a local car show this morning, got a SES right away. Read it when I got home, was P0442, Evap Emissions Control System Leak (small leak). I cleared the code, figure I'll drive a bit and see if it stays away.

Using the LS1M, I got the following info under the "Test Results" tab, can anyone elaborate on these results? Does the Yes mean each of these has a problem???? Seems highly unlikely.

Misfire Yes
Fuel Sys Yes
Components Yes
Evap System Yes
O2 Sensor Yes
O2 Sensor Heater Yes
EGR System Yes

Got this online, already retightened the gas cap, which is a 1 yr old GM replacement. If the code comes back, guess it's time to start replacing hoses.


This indicates a fuel vapor leak in the EVAP control system. It means a very small leak has been detected. In fact, the leak can be from a hole as small as 0.04" in diameter. The (EVAP) emission control system prevents the escape of fuel vapors from a vehicle's fuel system. Fuel vapors are routed by hoses to a charcoal canister for storage. Later, when the engine is running a purge control valve opens allowing intake vacuum to siphon the fuel vapors into the engine.


SymptomsYou likely won't notice any drivability problems.

CausesA code P0442 most likely means one or more of the following has happened:

A loose or improperly affixed gas cap
A non-conforming gas cap (i.e. not factory/original brand)
A small leak/hole in a fuel vapor hose/tube
Other small leak in EVAP system
Faulty vent o-ring seal
Possible SolutionsWith a P0442, the most common repair is to:

Remove and reinstall the gas cap, clear the codes, and drive for a day and see if the codes come back.
Otherwise, replace the gas cap, or
Inspect the EVAP system for cuts/holes in tubes/hoses

1998 Riv wrote:

I'm sure it's just a coincidence... let my wife drive the Riv yesterday as I needed her van to haul a ladder. Anyway, I drove it to a local car show this morning, got a SES right away. Read it when I got home, was P0442, Evap Emissions Control System Leak (small leak). I cleared the code, figure I'll drive a bit and see if it stays away.

Using the LS1M, I got the following info under the "Test Results" tab, can anyone elaborate on these results? Does the Yes mean each of these has a problem???? Seems highly unlikely.

Misfire Yes
Fuel Sys Yes
Components Yes
Evap System Yes
O2 Sensor Yes
O2 Sensor Heater Yes
EGR System Yes

if your wife put gas in the riv...... just go tighten the cap and clear the code......

98riviera98 wrote:

if your wife put gas in the riv...... just go tighten the cap and clear the code......

As I already stated, that's been done.

She didn't fill, was already 3/4 full. If it comes back later I'll have to start checking/replacing hoses.

1998 Riv wrote:

98riviera98 wrote:

if your wife put gas in the riv...... just go tighten the cap and clear the code......

As I already stated, that's been done.

She didn't fill, was already 3/4 full. If it comes back later I'll have to start checking/replacing hoses.

oh sorry man.... i DOUBT it will come back on

Code stayed away for the rest of the weekend, but came back on the way to work this morning. Tonight I took off the gas cap, and the sealing surface on the lip of the fill neck was pretty rusty and uneven. Got some sandpaper and cleaned it up pretty good, we'll see if it makes a difference tomorrow. No driveability issues, just an annoying dash light.

Seems I've fixed the problem for now, by cleaning up the sealing surfaces. I did find a hose or 2 that could have been an issue, snugged them up but didn't replace any yet. Only 1 appeared like it could be deteriorating a bit.