</>I recently began recieving the following codes on my 2001 alero.PO 128, PO 140, P 1189, and either U1040 or V1040 hard to read the typing. Normally what happens is I will be driving along and the thecheck engine light comes on and the rad fan begins to run constantly. I take it to my mechanic and clears the codes and everything goes back to normal. The lights goes off and I am good to go. He seems to think its the computer but a I am not totally sure.


As of today I have also found that my security is coming on in my car. The car does not stop running or have any problems when the light comes on. If anyone has an insight into these 2 problems it would be greatly appreciatedEdited by: tweak

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I DONT WANT TO BE A SMARTY BUT YOU NEED A BETTER MECHANIC.
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PO128= Never heard of it.


PO140= Oxygen sensor circuit - no activity detected (downstream sensor)


P1189= Engine oil pressure switch circuit


Never seen the other two codes before either.


I agree with ilikecars. Sounds like your mech don't know what he is doing.&lt; src="http://www.google-analytics.com/urchin.js" =text/&gt; </>&lt; =text/&gt; _uacct = "UA-939292-46"; urchinTracker(); </>&lt; src="http://www.google-analytics.com/urchin.js" =text/&gt; </>&lt; =text/&gt; _uacct = "UA-939292-46"; urchinTracker(); </>
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The reason he said he thinks is the computer is because has checked everything else diagnostically and can't finy anthing wrong.. He can't explain why the codes just randomly showing up and why when you clear them the only thing that changes is the cooling fan constantly running.The car does not run any different when the codes are up..Edited by: tweak

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<TABLE style="WIDTH: 506px; HEIGHT: 42px" borderColor=#0000ff width=506 border=1><T><T>
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<TR>
<TD vAlign=top>P0128 </TD>
<TD vAlign=top>ECT Below Thermostat Regulating Temperature(GM) </TD></TR></T></T></T></TABLE>



<TABLE style="WIDTH: 464px; HEIGHT: 42px" borderColor=#0000ff width=464 border=1><T><T>
<T>
<TR>
<TD vAlign=top>P0140 </TD>
<TD vAlign=top>O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 2) </TD></TR></T></T></T></TABLE>



<TABLE borderColor=#0000ff cellPadding=2 width=420 border=1><T><T>
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<TR>
<TD vAlign=top>P1189 </TD>
<TD vAlign=top>Engine Oil Pressure Switch Circuit </TD></TR></T></T></T></TABLE></>
<TABLE width=531 align=center border=1><T><T>
<T>
<TR>
<TD align=middle width=116>U1040</TD>
<TD align=middle width=399>SCP (J1850) Invalid or Missing Data for Vehicle Speed </TD></TR></T></T></T></TABLE>





Thats all I can find about the codes... that last one would make me think that some is wrong with the computer.</>
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How long have you owned the car and when did this start happening? You can get the PCM reflashed at a dealer.
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First, about your security issue: Does the security light flash when you try to start the car, and continue flashing after a failed start attempt? Have you tried using a less worn key? Is your keychain heavy? A worn key or heavy keychain have been known to cause wear in the ignition cylinder, causing the sensor in there to signal a theft attempt.


If you are sure you have a PK2 (PassLock II, the name of your security system) problem, here is a permanent solution. http://www.automotiveforums.com/vbul...thread.php?t=6 98861&amp;highlight=passlock+bypass


I have done this myself, and it does work. Search for my thread about how to bypass Passlock for detailed directions and diagnosis steps.


About your other problems: The fans run because the computer detects a problem with the temperature sensing system. It cannot determine the correct coolant temperature, so to protect the engine, it turns the fans on constantly, in case the engine is overheating.


An o2 sensor costs about $100 and can be installed in 15 minutes. I think the downstream one is just there to check operation of the catalytic convertor, and doesn't really affect engine operation at all.


How did your mechanic check these items?
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