If you own a car, then you must know about the OBD scanner. These onboard diagnostic tools mainly use a self-diagnostic system that also gives reports about the car issue. This device explicitly provides the owner access to information about the status and performance condition of the engine of the vehicle. You see, two specific parts are in every diagnostic device: connector and pinout. Electrical signaling protocols are also attached to this scanner with a messaging format. From this, you can learn about all the details of the vehicles.
This scanner has five communication protocols. Every car brand has its own choice, so they choose each protocol according to their needs and preferences. From here, we are talking about the SAE J1850 PWM bus system. Let us check every detail of this application on the car.
SAE J1850 PWM
| Feature | Description |
|---|---|
| Bus State: | Active when BUS + is pulled HIGH, BUS – is pulled LOW |
| The number of bytes: | 12 |
| Bit Timing: | ‘1’ bit – 8uS, ‘0’ bit – 16uS, Start of Frame – 48uS |
| GND: | Pins 4, 5 |
| 12V: | Pin 16 |
| BUS +: | Pin 2 |
| BUS -: | Pin 10 |
| Maximum Signal Voltage: | 5V |
| Minimum Signal Voltage: | 0V |
All about SAE J1850 PWM Protocol:
The SAE J1850 PWM is a specialized application for diagnostic and data sharing of car problems. There are two forms of this SAE J1850 PWM bus; those are 41.6Kbps PWM and 10.4 Kbps with variable pulse width. The PWM version has two different wire approaches. Here are all the details about the PWM version of the J1850 application.
The signal of this PWM runs at 41.6 Kbps, and most of this protocol is found in Ford brand vehicles. The SAE J1850 PWM is also defined as a class-B protocol for parametric data. That means this system can transfer parametric data between nodes so that it can eliminate the redundant sensor with another plan. On the OBD2 protocol, it gets bus+ in pin two and bus-in pin 10. The voltage pin is 16.
Similarly, GND has pins 4,5. This application can also be active on a bus, and it can pull it high when you use Bus+ and low when you use BUS-in an active state. The maximum voltage of this application is 5V.
You must be wondering why Ford used this protocol. This pulse width modulation can reduce the average power delivery with the help of an electrical signal. After that, it also successfully chopped the discrete parts into it. But there are also some disadvantages to this PWM system. It has a variable pulse width as well as different power contents. So if the transmission is powerful enough to get the maximum width and pulse, then it can transmit average power, which is low, like 50% of the old power.
Conclusion
This SAE J1850 PWM also supports various Android apps such as Torque Pro, OBD Car Doctor, and others. Simply enable Bluetooth, and you can get multiple sensor data, diagnose those, and check the car engine malfunction light, among other things. And this protocol is also popular as Ford’s communication protocol. Each bit of information in this system is 24 us long with a variable voltage pulse width to present the logic of 0 and 1.
References:
https://www.researchgate.net/publication/240996684_SAE_J1850_Protocol
https://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.506.6682