Mid-2009 Hardware Test Error

Discussion in 'MacBook Pro' started by 121a, Sep 14, 2013.

  1. 121a macrumors newbie

    Sep 14, 2013
    Hello everyone, new to the forum but not new to tinkering with computers. I have had my Mid-2009 Macbook Pro 15.4" with Duo 2.53ghz for the last three+ years and it has been a good computer. The most expensive repair was a top case a while back for $250. For the most part I was able to do all other repairs myself (SuperDrive repair/upgrade to SSD/replace SuperDrive with a HDD caddy). Up until recently it functioned perfectly. Now it still does except the fan.

    A week ago the fan just out of the blue, spun up to its max of 5,700rpm. No reason. Temperature of the CPU is 98F-100F using smcFanControl. Performed an AHT and it returned the following problem:
    4SNS/1/40000000: TC0D- 128.000

    I accidentally interpreted this to be a palm rest temperature sensor and replaced the trackpad today. Well, now the fan is randomly spinning up and down from 2000-5700. It is extremely annoying and other than the noise, the computer functions just fine. I would like to get it silent again. Any ideas what can be causing this odd occurrence?

    From what I have read, it is a CPU temp sensor, but my sensor readout is not fluctuating. I have reset the SMC and PRAM multiple times, nothing helps. Is there something loose or is something much harder to fix happening?

  2. nerfologist, Sep 16, 2013
    Last edited: Sep 16, 2013

    nerfologist macrumors member

    Jun 14, 2013
    I own a MacBook Pro 15" mid-2009 2.66 GHz. I have been experiencing a fan issue similar to yours ever since mid-2010 (1 month after the warranty expired) :(

    In my case, some of the temperature sensors will drop to a ridiculously low value (likely the result of an overflow), then the readings disappear completely.

    I include a reading of iStat with temperatures (notice some are missing) and fan speeds (both maxed out at 6200 rpm).


    Do you have a similar situation?

    In my case, it should be due to defective temperature sensors on the logic board. Based on my research, they are not replaceable. A logic board substitution is currently beyond economic repair, as I'm keeping the money for my next Mac.

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