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I have a 2005 Mazda 3 (SP 2.3), and the check engine light came on. I went out and bought a code reader that told me there are 2 codes. The first being the P0128 code and then the second is showing up as P0128 as well, except there is something that shows up right before the up and down arrows on the right side.

First Question: What is this second code shown below?

I looked around online and found this question that was definitely helpful on knowing what to look for. Since I imagine my coolant level is just fine, my Second Question: Should the problem be the thermostat itself, where is it and how do I change it?

UPDATE: I have confirmed that my coolant level is just fine, within the min/max levels. Do I need to jump to changing thermostats, or should I flush the coolant first?

2nd Code

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Kept looking around online, and turns out this is how you change out the thermostat. ( – tarheel May 16 '13 at 1:48
up vote 2 down vote accepted

It means it's a pending code, in other words it's a current and history code that's why it's listed twice.

enter image description here

As for you second question, it's most likely a stuck open thermostat it could be a faulty Engine Temperature Sensor, but most of the time that will set a different code.

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So in other words, my "2 codes" is really just the one that is both before and after it has matured (aka crossed the threshold to make the check engine light come on). Correct? – tarheel May 15 '13 at 23:43
@tarheel Yes that is correct – Move More Comments Link To Top May 16 '13 at 0:00
@tarheel I updated the my answer to include your second question. – Move More Comments Link To Top May 19 '13 at 20:27

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