FEOA Forums banner
1 - 5 of 5 Posts

· Registered
28 Posts
Discussion Starter · #1 ·
I am getting a MIL (check engine light) and when I check the code it is a P0442 (i think because it has been awhile since I cleared it) Looking up the code I find that it is a "small leak in evaporative system" or something like that. So the first thing I do is purchase a new fuel cap from my local for dealer. I cleared the code after installing the new cap and thought for sure it would resolve the issue. Well, I am getting the code again after about 1 week of driving. I have checked the lines and do not see any obvious cracks or breaks. I have considered plugging the line from the tank where it attaches to the purge valve to see if the leak is in the line from the tank or the valve assemble itself. Does anyone have any past experience with this problem and are there any suggestions to help me resolve?

· Registered
803 Posts
Sorry,there is no such code.There is a:

P0442 - EVAP Control System Leak Detected (Small Leak)

The PCM monitors the complete EVAP control system for presence of a small fuel vapor leak. The system failure occurs when a fuel vapor leak from an opening as small as 0.10 cm (0.04 inch) is detected by the EVAP running loss monitor test.

Possible causes:

After-market EVAP hardware (such as fuel filler cap) non-conforming to required specifications,
Small holes or cuts in fuel vapor hoses/tubes,
Canister vent solenoid stays partially open on closed command,
Damaged, cross-threaded or loosely installed fuel filler cap ,
Loose fuel vapor hose/tube connections to EVAP system components,
EVAP system component seals leaking (EVAP canister purge valve, fuel tank pressure sensor, canister vent solenoid, fuel vapor control valve tube assembly or fuel vapor vent valve assembly),

And then you have :

P0402 - EGR Flow Excessive Detected

The EGR system is monitored for undesired EGR flow during idle. The EGR monitor looks at the DPF EGR signal at idle and compares it to the stored signal measured during key ON and engine OFF. The test fails when the signal at idle is greater than at key ON engine OFF by a calibrated amount.

Possible causes:

EGR valve stuck open ,
Plugged EGR vacuum regulator solenoid vent ,
Plugged EGR tube,
Slow responding DPF EGR sensor,
Damaged DPF EGR sensor,
Improper vacuum hose connection,
Plugged vacuum hoses,
EGRVR circuit shorted to ground,
Damaged EGR vacuum regulator solenoid ,
Damaged PCM,
A DPFEGR PID reading that is greater at idle than during key ON and engine OFF by 0.5 volt or a rough engine idle, may indicate a hard fault.


P0420 - Catalyst System Efficiency Below Threshold (Bank 1) Indicates Bank 1 catalyst system efficiency is below the acceptable threshold Use of leaded fuel

Possible causes:

Damaged HO2S
Malfunctioning ECT
High fuel pressure
Damaged exhaust manifold
Damaged catalytic converter
Oil contamination
Cylinder misfiring
Downstream HO2S wires improperly connected
Damaged exhaust system pipe
Damaged muffler/tailpipe assembly
Retarded spark timing
Compare HO2S upstream & downstream switch rate. Under normal closed loop fuel conditions, high efficiency catalysts have oxygen storage which makes the switching frequency of the downstream HO2S quite slow compared to the upstream HO2S. As catalyst efficiency deteriorates, its ability to store oxygen declines and the downstream HO2S signal begins to switch more rapidly approaching the switching rate of the upstream HO2S. Once beyond an acceptable limit the DTC is set.

Wich one is it?

· Registered
28 Posts
Discussion Starter · #4 ·
P0442 - EVAP Control System Leak Detected (Small Leak) is the code I am getting. Like I said, I have installed a new gas cap that I purchased at the local Ford dealer. It takes about a week (250 miles in 25 mile trips) to throw the code.

Is there a way to test the system. Maybe a leak down check from the purge valve back to the tank?

Where is the monitor located that checks for leaks?

· Registered
803 Posts
Its taking whats called an OBD cycle.It needs to see a certain criteria in
order to throw a MIL.Thats why it takes some time to trigger the MIL.
There are EVAP tests to examine the system.If you have access to a WDS Or a smoke generating machine youd be able to perform the tests.Unless you work in a major autoshop,I find it difficult for you to be able to find these machines.You might have to bite the bullet and have it diag at a ford dealership.
1 - 5 of 5 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.