01 t&c with po134 & p1495 codes

QuestionEdit

QUESTION: Roland, I know what the codes are, but I get a loud sucking sound when I remove the gas cap. Could this be caused by the leak detection pump solenoid being defective

ANSWER: Hi Gene, Is the sound produced only when the engine is idling, or also when you simply turn the key the run position but don't start the engine? Let me know and in the meantime I have reviewed the troubleshoot for the 1495 code. The 0134 is about the upstream oxygen sensor and not apparently involved in this noise. The manual says that the code can be caused by an intermittent connection between the pump and either the pcm or the power supply to the pump, or internal to the pump. The first test requires a diagnostic readout box to request the pump to actuate, and in the absence of that let us set aside that test. Remove the plug from the LDP. Then turn on the ignition switch and check for the presence of 12v at the pink/gray wire on pin 3. Turn off ignition switch. Remove the plug from both the LDP and the 40-pin plug at the pcm (left inner fender by the battery and the power box# which contains wires 41-80. The wire assignment numbers are etched into each of the two pcm plugs. Then verify that the resistance to ground from pin 2 at the LDP plug is infinite #i.e. the wire is not shorting to ground#. Then measure the resistance between pin 2 of the LDP plug #violet/light blue# and pin 77 of the pcm plug and that should be a dead short which indicates a good connection between the plugs is present. I would then repeat the previous two tests between pin 1 of the LDP plug #violet/white# and pin 72 of the pcm plug in order to test the last item in the LDP circuit. Having successfully accomplished those 5 measurements I would conclude the the LDP is defective because that is the only other possibility that can be present, and thus assume that the test that required the diagnostic readout box would have failed, the conclusion of which is to replace the LDP. So in answer to your question, if you check there is voltage to the plug and that the other two wires are neither shorted to ground or open, then indeed the code could be caused by a defective LDP. Presumably the noise you hear is due to such a failure allowing the intake manifold vacuum to be experienced by the fuel tank all the time rather than in a controlled manner. Please 'rate' my answer #see below#. Thanks, Roland

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QUESTION: Roland, thank you for your response. The sucking noise happens when I turn off the ignition and open the tank to fill with gas. I have not tried it running Gene

AnswerEdit

Hi Gene, I have not experienced such a situation but with the ignition off and having the noise, but either there is a residual vacuum in the system which normally would be 'bottled up' when the key is off and so you hear the air rushing in to fill that vacuum (which would suggest that the noise will decrease quickly) OR the sound is that of the leak detection pump which is erroneously being powered when the key is in the off position. So I would check to verify that there is power on pin 3 of its plug when the key is in the 'run' position, and that there is no power on pin 3 when the key is off. That being the case I would believe that there is a problem with one of the vacuum check valves inside the pump which is failing to close when the pump is turned off. And if that is the case, then unless you wish to try to open the pump and repair it then a new pump would be the logical alternative. If you find that the pump is getting 12v on pin 3 with the key off, then we need to trace out that problem and correct that. Please 'rate' my answer. Thanks, Roland