[SOLVED]820-3437 Failed PBUS sensor

JohnB8812

New member
Mac runs normally and charges battery. PBUS sensor in hardware profile says zero volts. I replaced Q5500 and checked the resistors and cap on the circuit line and everything measures ok. PPBUS without a battery is 8.58 volts. With a battery, it starts at 7.6 with the machine off and the charger plugged in then as it boots it goes up to 8.4 volts. The battery is only at 15%, so my question is once again

1. Does this matter and should I stress over it?
2. Could the sensor be pulled down by a old or shit battery?
 

dukefawks

Administrator
It should certainly not read 0V. Also you replace stuff before measuring? Q5500 pin 4 is the input and pin 3 the output then a voltage divider and to the SMC. Measure first.
 

JohnB8812

New member
So Q5500 has 8.58 volts on input but zero volts on output. SMC_SENSOR_PWR_EN is 3.42 volts. R5503 measures normal but R5504 measures 4.56K not 5.49K. This may be a dumb question but is R5504 bad or could something else be making that measurement low?
 

JohnB8812

New member
Replaced Q5500 now power passes through it still fails sensor test. Measured R5501, R5503, and R5504 and they all measure correctly now. R5504 is now 5.49K. C5504 is not shorted. Does this mean crap under the SMC is failing the sensor test?
 

aprendiz

Moderator
You should have about 4.3V on pin 5 and 8.5V on pin 3, if not, maybe a broken trace or bad resistor between pin 4-R5501-R5502-pin 6....
 

aprendiz

Moderator
Apply some flux and heat, most of the time this works....

Yes, if you have 1.4V at SMC_PBUS_VSENSE Q5500 is working properly
 

JohnB8812

New member
Zero dice. Sensor still fails despite reflow. Would this mean SMC is partially dead or would this be anything else? I'm out of ideas on this one.
 

JohnB8812

New member
Ok now I feel dumb lmfao. The only thing I didn't try was a different battery. With a FOR SURE known good, it passes the sensor lmaooooo. The battery that was with the machine says condition NORMAL in the OS, but it causes the sensor to fail. All that for a DAMN BATTERY LOL that sucks but mark this as sovled
 

JohnB8812

New member
Also learned a partially bad battery will cause VP0R to fail. Learn something new every day! Thank you Duke and apprendiz for the help tho I really appreciate it.
 

JohnB8812

New member
Tested with the battery still fails sensor. With known good it passes so battery toast. Board fixed tho thank you to all you guys glad this worked out!
 
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