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Forum > Emissions Component > Question

2003 Toyota Sienna P0456 and P0450

2003 Toyota Sienna (about 149,000 miles). The check engine light continues to re-appear, despite repairs. It's been very difficult to diagnose, at least for a regular repair shop.

7-18-15: First noticed that the Check Engine light was on (steady, not flashing). We took it to our small auto repair shop, which we have used for many years, but it is not a smog station.

7-21: The repair shop pulled trouble P0456 from the OBDII. I replaced the gas cap. The light eventually came back on. 

8-27: P0450. We injected smoke into EVAP system and found a cracked section of hose. We replaced the EVAP hose near the gas tank. We removed a cover to get access to the gas tank. The check engine light eventually came back on. 

9-17: EVAP trouble code again. We replaced the vacuum valve switch-vT (90910-12209). The light eventually came back on. 

10-28: We cleaned and replaced O-ring in or near charcoal canister. 

11-7: The light came back on. 

At this point, we are thinking of taking it to a smog test and repair station, hoping they are better equipped and trained for this type of diagnosis and repair.

Do you have any suggestions? Thank you so much for your time and expertise!!


Answer:

We'd have to recommend that you do in fact get your Toyota Sienna diagnosed by a smog check repair station, and one which is STAR certified. STAR certified smog check and/or test facilities must pass the Bureau of Automotive Repairs' highest inspection standards.

As for the Toyota Sienna trouble codes, if trouble code P0450 reappeared, and you are certain you've replaced the Pressure Sensor Switch with a good working part, we'd recommend ensuring the wiring and wiring harness to the switch is not damaged or defective. P0450 is a hard fault indicating a problem with the pressure switch. The switch might be defective or its wiring damaged, and once repaired, the trouble code will clear itself within a day or two. 

If P0456 reappeared, the fault will require further diagnosis. P0456 is a very vague EVAP trouble code which simply says, there is a leak in the EVAP system. The location of the leak is not referenced at all. It will require a smog technician diagnose the entire EVAP system, including gas tank.


posted by SmogTips Support

 

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