Apple MacBook Pro A1502 820-3476-A Slow / Fan full on

[REpairAT]

Hi,
got this defective Notebook. It boots, but CPU is throttled and fan always 100%.

MacBook Pro Core i5 2.6 13" Mid-2014
A1502
EMC 2875
Mainboard 820-3476-A

I know, this fault is most likely a defective temp sensor, but Apple Diagnostics is useless (PFM006, PPN001 & NDC001) and TG Pro also does not show any issues. Any idea where to start? Thanks!

[mon2]

Re: Apple MacBook Pro A1502 820-3476-A Slow / Fan full on

Disconnect the trackpad cable and test again.

[REpairAT]

Re: Apple MacBook Pro A1502 820-3476-A Slow / Fan full on

Disconnect the trackpad cable and test again.

Hi, same story

[mon2]

Re: Apple MacBook Pro A1502 820-3476-A Slow / Fan full on

The board features numerous SMBUS masters, each using the SMC IC.

Remove all power. Meter in resistance mode. Check the resistance to ground of each SMBUS SCL & SDA line. Checking to see if any of the SMBUS lines are stuck.

[piernov]

Re: Apple MacBook Pro A1502 820-3476-A Slow / Fan full on

Run ASD instead of AHT/Diagnostics. Also several sensor reading software won't show erroneous sensors so they are useless in this situation.

[REpairAT]

Re: Apple MacBook Pro A1502 820-3476-A Slow / Fan full on

Run ASD instead of AHT/Diagnostics. Also several sensor reading software won't show erroneous sensors so they are useless in this situation.

Thanks! I had no idea of it's actual existence.
TA0P - Ambient Air Sensor

[mon2]

Re: Apple MacBook Pro A1502 820-3476-A Slow / Fan full on

Have you replaced the SSD / drive ?

[REpairAT]

Re: Apple MacBook Pro A1502 820-3476-A Slow / Fan full on

Have you replaced the SSD / drive ?

No, it all looks original. My only info was, that the screen got replaced by Apple, years ago.

[mon2]

Re: Apple MacBook Pro A1502 820-3476-A Slow / Fan full on

If I am following this thermal sensor correctly, you should have a 2 wire transistor that must be applied onto the body of the SSD / drive for thermal checking. Do you see any such piggy backed device on the SSD ?

If not, you can make your own using a cheap transistor - we have done this in the past.

[REpairAT]

Re: Apple MacBook Pro A1502 820-3476-A Slow / Fan full on

If I am following this thermal sensor correctly, you should have a 2 wire transistor that must be applied onto the body of the SSD / drive for thermal checking. Do you see any such piggy backed device on the SSD ?

If not, you can make your own using a cheap transistor - we have done this in the past.

That's the closest I could find.

[mon2]

Re: Apple MacBook Pro A1502 820-3476-A Slow / Fan full on

Yes, that very well may be a thermal sensor. Where is this located? Near your SSD?

[REpairAT]

Re: Apple MacBook Pro A1502 820-3476-A Slow / Fan full on

Yes, that very well may be a thermal sensor. Where is this located? Near your SSD?

It's on the SSD Board itself

[reformatt]

Re: Apple MacBook Pro A1502 820-3476-A Slow / Fan full on

I have had an instance of a bad SSD cause throttling on an A1466. It's rare but does happen occasionally, usually after liquid damage.

[piernov]

Re: Apple MacBook Pro A1502 820-3476-A Slow / Fan full on

Set ASD to continue on error to see if there are other bad sensor readings.

[REpairAT]

Re: Apple MacBook Pro A1502 820-3476-A Slow / Fan full on

Set ASD to continue on error to see if there are other bad sensor readings.

Thanks, it was absolutely stupid to cancel after the first result.
So here we have:

TA0P (Ambient Air Sensor)
TC0P (CPU Proximity)
TM0P (DDR3 Proximity)
Th1H (Right Fin Stack Proximity)

... and I assume, each of them is read by U5870 on the picture, mon2 shared above. I will focus on this and report. Thanks so far!

[mon2]

Re: Apple MacBook Pro A1502 820-3476-A Slow / Fan full on

As per above suggestion, review the smbus lines that drive this common sensor ic. If the lines are stuck, they will all fail. Measure the voltage to ground of the SCL and SDA lines for this group.

[REpairAT]

Re: Apple MacBook Pro A1502 820-3476-A Slow / Fan full on

As per above suggestion, review the smbus lines that drive this common sensor ic. If the lines are stuck, they will all fail. Measure the voltage to ground of the SCL and SDA lines for this group.

Quick update, was busy last week: Job is done! Thanks again for your support. Under the microscope, the issue was obvious, no idea how I could miss it first. All working fine now.

BR!

[mon2]

Re: Apple MacBook Pro A1502 820-3476-A Slow / Fan full on

Now, THAT is a nice cleaning job!!