Could use some help!
Been battling a CEL for a few months now. Purchased a new cap, pulled and checked the solenoid valve with 12v, cleared the code and it came back on. Then changed the cap with one from another vehicle, sanded, cleaned and lightly oiled the corroded surface the cap mates with and did a visual inspection of the parts near the right rear tire. After I cleaned the tank inlet, I cleared the code, and I drove over 150 miles and it was still pending. Found the Mazda cycle for their procedure for clearing it where you idle for 5 minutes from a cold start, rev to whatever for 15 seconds, drive at 52-55 for 90 seconds and BAM the damn light kicked on. This is getting old. I rarely drive it, and would like to sell it with a cleared CEL.
It's a 2003 5 speed, with 112,000 miles. Clean Atlanta Georgia vehicle. No rust. i.e., all connections are clean. I don't have a decent local mechanic that I trust, same goes for the dealership.
Any ideas or help would be greatly appreciated.
Don
Do you mean codes P0455 (there is no 445) and P0441? Check out the causes, there's some overlap there. Here's the list of causes from the factory manual.
DTC P0441
Evaporative emission control system incorrect purge flow
DETECTION CONDITION
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PCM measures the purge line pressure, which is the vacuum when a following condition. If vacuum between charcoal canister and intake manifold does not reach the specified, PCM determines that the EVAP system has clogging.
- Diagnostic support note
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This is an intermittent monitor (Evaporative system monitor).
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MIL illuminates if PCM detects the above malfunction condition in two consecutive drive cycles.
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DIAGNOSTIC MONITORING TEST RESULTS and PENDING CODE are stored if PCM detects the above malfunction condition during first drive cycle.
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FREEZE FRAME DATA is available.
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DTC is stored in the PCM memory.
POSSIBLE CAUSE
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Purge solenoid valve malfunction
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Blockage in EVAP system
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Charcoal canister malfunction
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Catch tank malfunction
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EVAP hose damaged or loose
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EVAP pipe damaged
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Evaporative emission system leak detection pump malfunction
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Fuel pump unit poor seal
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Leakage in EVAP system
-
PCM malfunction
DTC P0455
EVAP control system leak detected (gross leak)
DETECTION CONDITION
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Remaining fuel 15—85%
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IAT at engine start -10—60° C {14—140° F}
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ECT at engine start -10— 35° C {14.0— 95° F}
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Atmospheric pressure above 72.2 kPa {542 mmHg, 21.3 inHg}
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Vehicle speed 39.5— 120.3 km/h {24.5— 74.5 mph}
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RPM 1000— 4000 rpm
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Calculated load 9.4— 65%
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Throttle opening angle 3.13— 31.6%
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IAT during monitor -10—60° C {14— 140° F}
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ECT during monitor 70—100°C {158—212°F}
- MONITORING CONDITION
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Target pressure (ftp 1): -0.993 kPa {-101.3 mmAq, -3.99 inAq}
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PCM monitors EVAP system when driving under following conditions:
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PCM measures the FTP (ftp1), which is the vacuum when a specified period has passed after the tank pressure has reached the preprogrammed target pressure and purge control valve has been closed while monitoring conditions are met. If FTP is below threshold, PCM determines that the EVAP system is blocked or has a large leak.
- Diagnostic support note
-
This is an intermittent monitor (Evaporative leak monitor).
-
MIL illuminates if PCM detects the above malfunction condition in two consecutive drive cycles.
-
DIAGNOSTIC MONITORING TEST RESULTS and PENDING CODE is available if PCM detects the above malfunction condition during first drive cycle.
-
FREEZE FRAME DATA is available.
-
DTC is stored in the PCM memory.
POSSIBLE CAUSE
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Purge solenoid valve malfunction
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Canister drain cut valve (CDCV) malfunction
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Loose, missing or defective fuel filler cup
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Charcoal canister malfunction
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Catch tank malfunction
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Rollover valve malfunction
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Cracked fuel tank
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Fuel tank component parts poorly installed
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EVAP hose damaged or loose
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FTP sensor malfunction
Incorrect purge flow is almost always a stuck open purge solenoid. Very easy to test: find the purge solenoid, disconnect it from the hose that goes to the back of the car (IE the hose that connects it to the intake manifold is still connected), unplug it, start engine. If you have vacuum on the now-open side of the purge solenoid, it's bad. It should not pass any engine vacuum at all with no power to it, unplugging it ensures that it isn't getting powered up.
If there is black dust or, worse, pellets in the line going to the purge solenoid, that is the charcoal canister breaking up internally, which is why the purge solenoid is sticking open in the first place.
Looking more closely at what Mazda claims are the test conditions and fault criteria, both may also be set by a vent solenoid that is failing to seal. This one is not as easy to test 
The easy way with a scan tool involves closing the vent solenoid with the purge solenoid open, watching for a change in tank pressure. Assuming your scantool allows this. Most are not as friendly so one has to get out a smoke machine with a flow ball and a Power Probe to actuate the solenoid...
Man, you guys are quick.
Thanks Keith. 10-4 on my code mixup. I was going off of memory. Some kid (2 owners ago) replaced the fuel pump I was told. I'll look into that. Make sure it's sealed well.
Pete, I checked that, and pulled it to make sure 12v would click the solenoid. I just rechecked it, no vacuum.
Appreciate the input!
Don
Keith Tanner, many thanks! It was the fuel pump poorly sealed. Previous (young) owner installed a fuel pump and stripped out a few screws. Now I can sell it, and still sleep at night. After 10 Miatas, I've moved on to Volvo Amazons! ;-)
