Do a door sensor need to be that sophisticated? What the door sensor use for?

1) door sensor can be just a contact switch. An On/Off signal to the ECU. No electronic require inside. Keep it simple, cheap and failsafe.

2) If there require some crazy electronic stuff inside the switch, the circuit can be design to take wide range of voltage. 10-14.4v is enough to operate and tackle the low/high voltage of the battery. Battery don't drop dead till 0v.

1. TPMS Control Module Malfunction
The TPMS relies on a control module (ECU) to receive and interpret signals from tire sensors.

A weak car battery may cause:

Voltage drops during engine cranking.

Intermittent power supply to the TPMS module.

Faulty initialization of the TPMS system on startup.

This can result in the system failing to recognize one or more tire sensors.

2. Sensor Signal Issues
Some TPMS systems (especially indirect types) depend on stable vehicle electrical systems.

If the battery voltage is low, radio frequency (RF) signals from the tire sensors might not be processed properly, leading to:

Missed sensor readings

False TPMS warnings

3. BCM (Body Control Module) Glitches
TPMS often interacts with the BCM or other vehicle computers.

A weak battery can cause these modules to:

Glitch or reset

Lose stored configurations

Trigger diagnostic trouble codes (DTCs)

These issues can mimic or cause TPMS failures.

4. Startup Sequence Disruption
When starting the car with a weak battery, voltage may dip below the required threshold for proper ECU function.

This can interrupt the initial communication handshake between the TPMS control unit and tire sensors.

5. Battery Disconnect History
If the weak battery has recently been disconnected or replaced:

Some TPMS systems need to be reinitialized or relearned.

If this process wasn’t completed, the system may continue to display faults or fail to recognize sensor IDs.

. Incomplete Combustion and Poor Engine Operation
A weak battery can cause poor spark plug performance or weak ignition, especially during startup.

This leads to incomplete combustion, potentially causing:

Increased carbon monoxide (CO) emissions

Rough idling and engine misfires

If there's a leak in the exhaust system or poor ventilation (e.g., idling in a closed garage), carbon monoxide could enter the cabin.
➡️ Carbon monoxide exposure is a major cause of headaches and can be life-threatening.

🌬️ 2. HVAC and Ventilation System Malfunction
Some modern cars use electrical actuators for air recirculation and ventilation.

A weak battery may cause:

Blower fan issues

Stuck air recirculation flaps

Reduced fresh air flow

This can lead to stale air, higher CO₂ buildup, or inadequate cabin ventilation, which may trigger headaches, especially on longer drives.

⚠️ 3. Electronic Glitches and Stress
A weak battery can cause unpredictable electrical behavior:

Dash warnings

Radio or infotainment malfunctions

Flickering lights

This can increase driver stress or anxiety, which is a common headache trigger.

🚗 4. Cabin Air Quality Degradation
A weak battery may reduce the performance of systems that support:

Cabin air filters

Air ionizers or purifiers (in luxury vehicles)

This can let in more pollutants or allergens, which can cause sinus headaches or migraines in sensitive individuals.

🧠 Summary
A weak battery won’t directly cause headaches, but it can indirectly contribute by:

Leading to carbon monoxide exposure

Reducing ventilation quality

Causing vehicle stress or malfunctions

1. Poor Cabin Lighting and Instrument Visibility
A weak battery can cause:

Dim dashboard lights

Flickering displays

Inconsistent interior lighting

This can strain your eyes, especially in low-light driving conditions or at night. Straining to see instruments or road signs can cause:

Blurry vision

Eye fatigue

Temporary visual discomfort

💨 2. Faulty HVAC and Ventilation (Dry Eyes)
Battery-related issues can affect the HVAC system:

Weak fan motors

Non-functioning defogger or heater

Poor humidity control

This can lead to:

Dry eyes from low humidity or stale air

Foggy windshield making you squint or strain more

Dry or irritated eyes can temporarily reduce visual clarity and comfort.

🧠 3. Headaches and Fatigue (Perceived Eye Problems)
As mentioned earlier, a weak battery can cause:

Cabin air quality issues

Increased CO or CO₂ exposure (from poor combustion or poor ventilation)

Stress from warning lights and malfunctions

These can lead to:

Headaches

Brain fog

Fatigue

All of which can feel like poor eyesight when it’s actually more about cognitive and visual processing fatigue.

🔌 4. Flickering or Unstable Screens
Infotainment systems and HUDs may flicker or reset with low voltage.

Eye strain can come from trying to read a flickering screen or adjusting constantly to unstable lighting.

❗ If You’re Concerned About Your Eyesight
If you're noticing visual symptoms while driving, don’t ignore it — especially if accompanied by:

Dizziness

Nausea

Lightheadedness

A feeling of pressure behind the eyes

Also rule out:

Carbon monoxide exposure (very serious)

Underlying vision issues that worsen in low light or high contrast

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Fyi, .......

Gemini AI Overview

Yes, a weak 12V battery can potentially cause door sensors to fail or malfunction. Sensors rely on a consistent and adequate voltage supply to operate correctly. If the battery is weak or failing, it may not provide the necessary voltage for the door sensor to function properly.

Here's why a weak battery can affect door sensors:
- Insufficient Voltage:
Sensors require a specific voltage to operate. A weak battery may not provide enough power, leading to unreliable or inaccurate readings from the sensor.
- Intermittent Operation:
Even if the battery isn't completely dead, it might fluctuate in voltage, causing the sensor to operate intermittently or incorrectly.
- System Malfunction:
A weak battery can also affect other vehicle systems, including the car's computer, which might influence the operation of the door sensors.
- Other Factors:
While a weak battery is a common cause, other factors like wiring issues, sensor failures, or problems with the vehicle's computer can also contribute to sensor problems.

If you're experiencing issues with your car's door sensors, it's always a good idea to have your battery checked and ensure it's providing the necessary voltage. 
.

Nope.

Sensors if they are electronics, usually 5V and 3.3V requires to be regulated. This regulation comes from buck converters. 
When the EV is powered on the onboard DC/DC takes over , and the battery acts more like a capacitor rather than a battery.

Nope . Electronic sensors are regulated.
A car computer or ECU do not use direct 12V. It goes through buck conversion or down conversion. 
The regulator will work all the way down to 6-7V assuming the output is 5V.
And all this design criterias like load dump, voltage fluctuations are all already taken care off by the ECU power supply unit.

Also it is CLEARLY stated in the article , that it is not caused by the 12V battery.  So why are you trying so hard to try to link it back to the 12V battery again?

I am not protecting the west. I’m saying it like it is.
When there is a problem with a west product, I don’t have an issue calling it out.

But your argument on “Tesla is the same” in this context is not valid. The article that was shared says there was an accident because the driver chose to ignore fsd warnings.

He said, "I was driving to work, running FSD, a car came by, then the steering wheel turned very fast, took the car into the ditch by the roadside, hit a tree on the side, and the car overturned. I didn't have enough time to respond." Even though he was focused on the road, he didn't get to control the car, causing his car to overturn and stop in a state of upside down.

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Are you saying an EV car's weak or failing 12V battery will not cause it's door sensors,  "starter" function, comfort functions, control units and actuators to fail.? .......

https://www.varta-automotive.com/knowledge/...the-12v-battery - Electric vehicles and the 12V battery
Let's have a look at the many different xEVs on the market and the role of the 12V battery inside all of them.
.... And technically speaking, one could still call it a starter battery for "electric cars". When the vehicle is parked, the high-voltage battery is disconnected from the electrical system for safety reasons. If the journey is to be continued, the high-voltage battery must first be started - and it is precisely this starting process that is initiated by the 12V battery.

The vehicle's 12V network supplies comfort functions, control units, sensors and actuators. ...

Remember, in the original thread about this BYD incident, the initial diagnosis by the BYD SC was 12V battery fault. Today, Sime Darby says it's door sensor fault. The two could be very related, ie ...
12V battery fault ---> door sensor fault ---> the original BYD incident.
.

Are you saying an EV car's weak or failing 12V battery will not cause it's door sensors,  "starter" function, comfort functions, control units and actuators to fail.? ......

https://www.varta-automotive.com/knowledge/...the-12v-battery - Electric vehicles and the 12V battery
Let's have a look at the many different xEVs on the market and the role of the 12V battery inside all of them.
[color=green] .... And technically speaking, one could still call it a starter battery for "electric cars". When the vehicle is parked, the high-voltage battery is disconnected from the electrical system for safety reasons. If the journey is to be continued, the high-voltage battery must first be started - and it is precisely this starting process that is initiated by the 12V battery.

Remember, in the original thread about this BYD incident, the initial diagnosis by the BYD SC was 12V battery fault. Today, Sime Darby says it's door sensor fault. The two could be very related, ie ...
12V battery fault ---> door sensor fault ---> the original BYD incident.

ECU and all are regulated.. the buck regulator or power supply are all designed to expect fluctuations in the 12V.
That's why when I read the AI generated answers , I already know it is rambling on something that they don't know about.

https://industrial.panasonic.com/ww/ss/technical/b13

Door sensor maybe 'not so complex ' part of the system.

However, if it is used in conjunction with, Anti-roll away car function. The feedback loop have one more un-relenting output, which is put on the Electronic Parking brake.

Further complexity in the loop, the car also detects the blind spot of the side of the door, being opened (if driver side, it will again give verbal warning) some others have intact, experience automatic braking because the car detected some object in blind spot, meaning the rear guard rail can also play a part in this particular situation.

Therefore if the sensor is giving bad data, and the car reacted to it by applying parking brake... It is an extraordinary situation where by, either, just let the car roll, which is what usually happens, our car with M6 as the car is rolling and door is not properly closed, the car does not pop the Parking brake, but add in another seat belt sensor, when it detects you remove the belt, it will pop the Parking brake.

Yes, those AI are BS.

ECU can run at very low voltage. Microprocessor can run at 3.3v. This is aslo a safety for a car where if battery drop to lowest 10.5v, the ECU still function and execute the safety necessary for the car. Even other component not function properly.

I want to know, what the door sensor signal is giving to the ECU?

A simple ON/OFF (Open/close door) signal. If in this, a simple door switch is enough. Even 10mv also can run the switch. Cause it doesn’t require power.

If the door require multi signal input, than sensor is required. So what multi input signal the door need to generate. beside just open/close?

The rest what you said, is the ECU process the signal from the door input.

I think so.. the emas system is the same lah.

But BYD if the big battery below 20% charge, it wont charge the small 12v battery, dunno if geely program it to be the same

In a already started car ...NO. The DC/DC converter will take over the battery when it is started.
Guess what, the ATTO3 was moving at 100km/h an hour, it has started.
This is a perfect example of not understanding the article.
You are taking a parked, standby vehicle scenario where the main battery is disconnected .
When the main battery is disconnected there is no DC/DC charging to the lead acid battery. This behavior is exactly the same as in an ICE car. If it is dead the car cannot start and a warning would be given.

When it has started and moving at 100km/h like the ACTUAL SCENARIO with the BYD ATTO3 , the battery behaves like a capacitor, whatever consumed will be replenished by the onboard DC/DC converter. You're talking as though the 12V is an AA battery where it never gets recharged and once it dies in the middle of the road it dies. First things first do you understand what a dc/dc converter does? It takes the main battery and charges the 12V lead acid while it's on the go. So if the whole system is powered by the on board DC/DC converter and charging the lead acid battery, why would the battery fail while it is moving?
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"The 2 could be very related". Yes and my headache could also be related to the 12V battery fault.LOL.
Official explanation already there and you still want to try to plotek.
Are you so afraid of BYD damaged reputation?

Meanwhile, Matsudah case macam mana?
Must be the seat sensor pulak

https://forum.lowyat.net/index.php?showtopi...ost&p=111589177
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Above repost fyi, ie if the 10 month old/20,000km 12V battery is weak, it  can fail while the BYD Atto 3 is being driven on the highway until  the BIG battery has <20% charge , even though the car had been started earlier by the weak 12V battery.
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Above repost fyi, ie if the 10 month old/20,000km 12V battery is weak, it  can fail while the BYD Atto 3 is being driven on the highway until  the BIG battery has <20% charge , even though the car had been started earlier by the weak 12V battery.

https://forum.lowyat.net/index.php?showtopi...ost&p=111589177
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Above repost fyi, ie if the 10 month old/20,000km 12V battery is weak, it  can fail while the BYD Atto 3 is being driven on the highway until  the BIG battery has <20% charge , even though the car had been started earlier by the weak 12V battery.
.

Another perfect example of not understanding the scenario.

BYD will not charge the 12V battery below 20% in a PARKED, STANDBY scenario. . 
In a car parked standby scenario, the main battery will "periodically" charge the 12V battery once the 12V battery crosses a certain voltage threshold.
The 12V will still drain.. slowly because it needs to keep the main computer alive.
These periodic charging will drain the Main battery until 20% ( i think should be lower than this), and then stop "topping up" the 12V battery once it goes below a certain %.

https://www.geekzone.co.nz/forums.asp?forum...&topicid=303207
You can read about it here.
This rule DOES NOT apply to a car turned on and running on the highway.

Why would they stop charging the battery at 20% and keep air-cond on ? They let you drive at 100km/h but stop charging the battery ? LOL  
Air cond consumes like 10X-20X more power and the software choose to keep air cond alive and stop charging the 12V while moving at 100km/h?
Seriously you guys actually believe that the software will keep all the non-critical system alive but stop charging the 12V battery?
With the air cond blower , In car entertainment, lcd screen coming from 12V, how long do you think it will last? The batteries are a lot smaller then ICE cars . How long do you think it will last?

Which Matsudah case ?