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P0459 Code - thoughts on diagnosing this code

2399 Views 4 Replies 3 Participants Last post by  Bryan Lutz
Hey guys, was hoping I could get your thoughts diagnosing this code. I’ve been trying to fix my small EVAP leak and just replaced the purge control solenoid (under the hood) and am now getting a high volatage code for it.

I took my multi meter to it and found the follow:

- very small resistance between harness terminals (35 ohms I believe)

- 12 V coming from one terminal and 0V on the other with the car off

- cycling 4.5V on/off from other terminal when car is on and in test mode

- stripped the cover from the wires about 5 inches to look for shorts and didn’t find anything

- car throws a high voltage code when harness is plugged into solenoid and a low voltage code when it’s unplugged.

Am I correct assuming there is a short?

Also on a side note is it possible to just disable the EVAP codes completely? I’ve been chasing this issue for 5 months now and getting nowhere.


Oh and I should add that the purge solenoid does not function in test mode but will work when I bench test it.
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It depends on where in the circuit the voltage is measured. You most likely have a load on the ground side of the circuit. Check for a loose ground.
Would you happen to know where I can find a wiring diagram? Would help me wrap my head around this much better.
Ok so did some more troubleshooting and can't figure out why the valve isn't operating.

- I get 12V when switched to AAC on terminal 2 and when I manually ground the valve it will operate

- When the car is in test mode terminal 1 will alternate between open circuit and grounded yet the valve won't function.

Any ideas where to go from here?


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Your problem is likely in the ECU. I have seen this many times before. A component in the ECU burns and causes this code to appear even though the wiring and EVAP valve are all good and aren't really shorted high.

There is a guy on ebay selling a kit to fix this.

They have a kit to fix the issue. I have fixed quite a few ECU's this way. Just make sure whoever installs the kit has good soldering skills.
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