Fixing a Passenger Airbag Active Vent error code on a 2017 Hyundai Sonata

May 31, 2017
I was called to a shop to program a newly installed air bag module on a 2017 Hyundai Sonata with less than 700 miles on the odometer

I was called to a shop to program a newly installed air bag module on a 2017 Hyundai Sonata with less than 700 miles on the odometer (Figure1). This vehicle was involved in a front-end accident with deployment of the front driver air bag and the driver seatbelt. The air bag module had to be replaced because on this particular vehicle once crash data is stored in the control unit, it cannot be cleared. There was no deployment of passenger-side components because no one was in the passenger seat during the accident. This is determined by the passenger occupant seat weight-sensing device that will prevent deployment if no one is sitting in the seat.

Figure 1

When I arrived at the shop, I plugged my Hyundai GDS scan tool into the car and selected the air bag reprogramming procedure. When I went to perform the task, the tool came back with an error code B176200, which sets when the air bag module will not accept the coding procedure. The coding of the air bag can be performed manually by inserting a specific alpha numeric number that reflects the components that are installed in the air bag system. If the coding information is incorrect, then the air bag module will refuse the coding. This code can be retrieved by installing the old module and reading the coding written to the old module, or you can retrieve the coding from Hyundai's website for a small fee. My Hyundai factory scan tool is online with the server so it will automatically insert the coding for me. So I was surprised that the module would not follow through with the coding process.

Figure 2

The air bag module on this particular vehicle does not have the capability to diagnose the air bag system for a fault until it is properly programmed, unlike other manufacturers that will create a laundry list of codes until the control module is properly configured. The scan tool does have a hidden feature that will put you in the right direction if there are no error codes present that are keeping you from coding the air bag control module. You simply highlight the coding error fault by clicking on it, then you click on "DTC Status" above the error code. A window will pop up showing you what current errors are creating the coding fault (Figure 2). The error fault displayed dealt with an issue of the passenger air bag active vent. I have never come across this device or even known it existed. I fully understand about deployable air bags, seatbelts, buckles and battery-positive pyro-tech devices, but I never knew about a vent being deployed. So this one I had to crash course. It just amazes me how much there is out there to learn on a daily basis. I just recently learned about the Starbucks Venti, and now I have to be schooled on the Hyundai Venti.

Figure 3

After doing some research, I found that certain manufacturers were now adding an active vent into front air bags that control the venting of the air bags after they deploy. By looking at the passenger dual-stage air bag, you can see the third plug for the active vent device (Figure 3). My big question here was how the active vent could have been deployed if the passenger air bag was never deployed and there was no one sitting in the passenger seat. There was a chance that the active vent circuit had high resistance in the connections because anything over 0.5 ohms in an air bag system can set off an air bag light.

I decided to install the old air bag control module and properly secure it so it would be grounded. It is very important to not just hang a module with the connector engaged because the mount in most vehicles serves as a ground feed for the module, and the module may not communicate with the scan tool. It is also a safety precaution to avoid accidental deployment of onboard air bag components. By installing the old module I would be able to diagnose the system because it was already configured for the vehicle. When I scanned the old module, I was surprised to only see the code B165000 for crash data stored in the system. There was no active vent error fault stored (Figure 4).

Figure 4
Figure 5

I now needed to test the active vent system wiring. This can be easily done by simply lifting the connector shorting bar tab on the top of the connector. This plastic tab is always destroyed in the field by inexperienced guys who don't know about its operation. Prior to pulling a plug off a deployable component, if this tab is not lifted first the connector will be damaged and there will be no way to move the shorting bars away from the component pins. This always results in a short-circuit code during reassembly. So by leaving the tab in the up position, it would allow the shorting bars within the active vent assembly to make contact with its pins and create a short-circuit code (Figure 5). This, in turn, is an easy way to prove out the wiring from the air bag

Figure 6

control module to the active vent device. If I pushed the shorting bar back in, then the active vent code disappeared. At this point there was nothing wrong with the circuit. There had to be something wrong with the new control module.

I picked up the new module to check for proper pin connections, and I was shocked at what I saw. The guy who secured the connector to the air bag module could not get a straight, clear engagement of the connector. He secured it on a slight angle and bent a few pins on the new control module (Figure 6). Lucky for this guy, I was able to use a fine pair of needle nose pliers to straighten out the damaged pins. I bolted the module back in place, secured the connector and attempted once again to program the module, and the scan tool was able to insert the coding with no problems (Figure 7).

Figure 7
Figure 8

Okay so now we're done, right? Not so fast because we now have an ABS light on the dash with a code C128504. This code relates to the Longitudinal "G" sensor not being calibrated (Figure 8). What the manufacturers did without you realizing it is they incorporated a Yaw sensor internal to the air bag module to measure longitudinal and lateral movement for vehicle turns and vehicle stop and go. This sensor is not accessible through the air bag system to calibrate. It is bussed to the ABS control module and all data acquisition and calibration procedures are done through the ABS menus.

Figure 9

There are criteria measures to be met prior to calibrating a Yaw sensor. You must make sure you are on level ground and that the vehicle is at proper curb height with the tires properly inflated (Figure 9). Once this is achieved, then you are ready to calibrate the sensor and now you’re finally done with the task of securing a new air bag control module into the air bag system. My only hope is that this story will enhance what you know or didn't know about the air bag systems of today.

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