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| How To Repair iPhone 12 Pro Max fake temperature warning | |
|---|---|
| Device | iPhone 12 Pro Max |
| Affects part(s) | Main Logic Board, Charging Port |
| Needs equipment | Screwdrivers, Hot Air Station, Tweezers |
| Difficulty | ◉◉◉◌ Hard |
| Type | Soldering, Part Replacement"Part Replacement" is not in the list (Soldering, Teardown, Part replacement, Cleaning, Software, BGA, General) of allowed values for the "Repair Guide type" property. |
Problem description
iPhone 12 Pro Max displays a “Temperature Too High” warning even when the device is physically cool. The phone may refuse to boot fully, disable charging, or throttle performance.
On this model, the fault is typically related to either:
- A faulty charging port (dock flex) affecting temperature sensor readings, or
- Separation / cracked solder joints between the AP and RF sandwich layers, interrupting RF temperature sensor lines.
Symptoms
- “Temperature Too High” warning on boot
- Device feels cool to the touch
- Charging disabled or extremely limited
- Warning appears immediately after power on
- Issue persists after:
- iOS restore
- Battery replacement
- No abnormal current draw on DCPS
Solution
Diagnostic Steps
- Confirm device is physically cool
- Measure current draw (should be normal idle)
- Check for obvious dock flex damage or aftermarket parts
- If available, test with known-good charge port
Repair Steps
Fix 1: Replace Charge Port (Recommended First Step)
- Replace the charge port with a known-good OEM or high-quality part
- Reassemble and test
✅ If warning disappears → fault confirmed in dock flex
Fix 2: Reball Sandwich Board (Permanent Hardware Fix)
If the issue persists:
- Split the sandwich logic board
- Inspect for cracked or cold solder joints
- Reball the lower (RF) layer
- Re-stack and test
⚠️ This is an advanced repair and carries risk to CPU, baseband, and data.
Fix 3: Data Recovery Only (Temporary / Bypass Methods)
⚠️ These methods are not permanent repairs and are intended only for data recovery.
Option A: Known-Good Bottom Board
- Use a known-good bottom (RF) board in an iSocket jig
- Allows temporary boot for data access
Option B: Temperature Sensor Bypass
Bypass the RF temperature readings by adding a 10 kΩ resistor to ground on the following lines:
- Pin 487 – NTC_RADIO_BB_SE
- Pin 489 – NTC_RADIO_PA_SE
This forces valid temperature values and clears the warning long enough to:
- Boot the device
- Back up data