This is a Mazda 6 2006 four cyl manual trans about 50,000 miles. Recently the check engine light comes on. Got AutoZone to read the code as P2402. I bought a code reader and when the light came on again I read two codes, one P2402 and one P2402 with what looks like "pd" behind it.
I found a writeup on the web that this is supposed to be for the evap system and sometimes it erroneously happens when the auto doorlock is used at the wrong moments.
However if it really is the evap system what should be repaired or replaced? The manual I bought does not mention this. Thanks.

 

Try a new gas cap.

 

New gas cap or Evap Solenoid

 

I did replace evap solenoid. The code is P0455.

From dealer invoice:


P0607ARX solenoid value assembly, R&R
1812 WM (N/C)
1 L3P9-18-740B VALVE, SOLENOID (N/C)

25214 Purge Solenoid 1.5 performed computer test and found code P0455 EVAP stored in system. Inspected vehicle for leaks though ids and system passed. performed smoke test to EVAP system and found no leaks. Activated purge through IDS and purge was ticking as it should. Performed Vacuum Test on Purge valve and found valve not holding proper vacuum. Replaced Purge solenoid and cleared code. Test drove Vehicle and retested system with IDS and system passed. F0008XDX, F0607ARX. Tech 1946.

 

I got a new gas cap yesterday. Usually takes one to two weeks to get a check engine light. Will report back.

 

Ok so after about 5 days the check engine light comes on again. The code is P2402 again. The gas cap does not seem to be the item here. Looking for ideas, but exactly where is the evap canister and pump on a 2006 Mazda 6? Looks like it could be a corroded connection or "Pump Module Fault". Thanks.

 

It is beneath the car above the fuel tank.

 

Well, the Mazda 6 manual that I found shows two canisters on the firewall behind the engine. However, when I open the hood I sure don't see that. I'd hate to find that this guy is right about the canisters being back there above the gas tank.

 

Don't know if this helps, but my '99 Protege has a "map" of the EVAP loop stuck onto the underside of the hood.
The two canisters referred to are the catch tank, connected directly to the purge valve, and the charcoal filter, which is on the tank side (it's not in the engine compartment on my Protege). You may find you can access some of the stuff via a hatch visible by removing the rear seats.
When you replaced the gas cap, did you get the replacement from Mazda. My shop manual warns that it's particular geometry is crucial to EVAP loop functioning and caps other than identical Mazda replacements can lead to EVAP loop failure DTCs.
The 'pd' you saw appended to the P2402 DTC means excessive pressure differential, and indicates that you have a slow leak problem somewhere in the EVAP loop. These can be an SOB to find. Do you have any telltale clues, such as a faint smell of gas in the engine compartment, around the rear seats, or when you open the trunk after leaving the car sitting overnight for example?

 

It is under the car above the fuel tank.