Missing airbag sensor - Pontiac G6 Forum
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post #1 of 13 (permalink) Old 05-02-2019, 09:04 AM Thread Starter
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Missing airbag sensor

Hi,

I recently bought a 2008 Pontiac G6 GT that had been in an accident and had different doors put on the passenger side. Before I bought it, I had my mechanic check out the "service airbag" message that appeared on the DIC display. He said it was just a sensor in the front passenger door and probably just needed to be replaced. Well after I bought the car and took it back to him, he discovered after pulling off the door panel, that there was no sensor or wiring for the sensor. He told me that without that side sensor, the entire airbag system will not function.

It appears that the replacement door was from an older model that didn't have the side airbag sensor. From my understanding, starting in 2008 ALL models came equipped with the side impact sensor.
So my first question would be is that correct?

I initially was looking for a new door from a salvage yard, hopefully the same imperial blue metallic. Finding a good door is proving to be challenging. I don't want to stick a lot of money into it because it is a car for my teenage son. Even though it is my kid's first car and not perfect, I still want the airbag system to work properly (and the door to be matching color) .

So I was thinking about a different approach. I wondered about buying a correct wiring harness and side impact airbag sensor from a salvage yard and install that into the "incorrect" door.

Is that the best approach? Would I be able to install the sensor inside a door that originally didn't come with one? How big of a pain would this project be? Can someone point me to a good diagram of the inside of the door and the wiring? Unfortunately, wiring is not my strong suit when it comes to auto repair, so hopefully the diagram is straightforward.

Any helpful responses are greatly appreciated. Thanks.
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post #2 of 13 (permalink) Old 05-02-2019, 11:43 AM
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I would buy a "correct" door in the wrong color, rusted out, bashed or otherwise damaged so it's cheap. Then you can transfer all the electricals to your door. The advantage is that you can see side by side the differences between the doors and modify your door as necessary. If there is anything in your door that makes it impossible to install the sensor, you haven't lost much.
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post #3 of 13 (permalink) Old 05-02-2019, 01:31 PM Thread Starter
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DXG6 thanks for the response. The problem with that is I can't seem to find a correct door for a cheap price. Some of the doors are even with no "guts" inside so wouldn't even have the wiring and sensor I need. I suppose for a visual aid, I could pull the door panel off of the front driver's door to compare and see where the sensor mounts.
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post #4 of 13 (permalink) Old 05-02-2019, 02:00 PM Thread Starter
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Also, can anyone confirm that ALL 2008 and up models had the side airbag sensor? That way, if I know this for sure it will help me find the correct wiring harness. Thanks.
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post #5 of 13 (permalink) Old 05-02-2019, 03:26 PM
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My understanding is that on the doors, the side impact sensors are actually pressure sensors rather than accelerometers. In a side impact, the door tends to give too much such than the accelerometer reading is distorted. So the automakers use pressure sensors instead.

Knowing that, I'd be concerned about making sure all the openings in the door - such as the drain holes along the bottom - are as close to stock as possible for a car with side impact detection. So that means getting a door as close to stock as possible. It may turn out that the differences between one with side impact detection and one without are trivial, but you want to be sure.

If no one here can accurately describe the differences, if any, then, besides looking for one at a salvage yard, you might look for someone who will let you look inside their door. Maybe you have a friend who has a G6 so equipped?

Another thought is to drop by a dealership and speak with a service writer. They might be able to tell you any key differences to be aware of.

After that, I'm with dxG6 looking for a junkyard door that still has it insides installed. Even if it's rusted out, it can be helpful.

HTH.

Doug

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post #6 of 13 (permalink) Old 05-03-2019, 01:07 AM
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Doug, I don't know what kind of sensor they used but I would find it difficult to believe they used pressure sensors. If I understand you correctly, you surmise they are measuring the ambient pressure of the door cavity, which is close to sealed. That would not work with the windows down, as the cavity is no longer seled to any degree and the pressure profile in a crash would be totally screwed. It would also not work if the impact causes the door skin to rupture.

Last edited by dxG6; 05-03-2019 at 01:09 AM.
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post #7 of 13 (permalink) Old 05-03-2019, 06:05 AM
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Quote:
Originally Posted by dxG6 View Post
Doug, I don't know what kind of sensor they used but I would find it difficult to believe they used pressure sensors. If I understand you correctly, you surmise they are measuring the ambient pressure of the door cavity, which is close to sealed. That would not work with the windows down, as the cavity is no longer seled to any degree and the pressure profile in a crash would be totally screwed. It would also not work if the impact causes the door skin to rupture.
Where I was recently working, we were making some accelerometer devices for various automotive applications including front/rear impact. I've tested a few of those

In the context of the side airbags, I was told by knowledgeable people that the side system had evolved to using pressure sensors, which I'm a little familiar with having sold the Motorola line years ago. I've had some of the same thoughts as you regarding the drawbacks of the pressure sensors in this app. My only thought is that the guys developing it were able to characterize the pressure profiles under the various conditions - window up/down, extra large door vent holes due to rust, clogged door vent holes due to whatever - and still come up with distinct profiles they could filter for and derive a clear blow/no-blow decision for the side air bags.

Another thought is using a combination of accelerometer and pressure sensors, but I was thinking it was pressure only (for the side system).

Doug

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post #8 of 13 (permalink) Old 05-03-2019, 08:42 AM
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Side impact drawings

Drilling down on this some more, I found 2 electrical drawings showing the side sensors and airbags, and one for the door wiring, which does not include the sensor (d'oh!).

A fourth drawing for side impact (SIS) shows the driver's door. In it, the sensor appears to be on the bottom of the door toward the rear. I assume the passenger side would mirror that.

The schematics show the side impact sensor as a switch, so whatever the underlying mechanism is - accelerometer, pressure sensor or both - is masked by the signal processing in the sensor that reduces the sensor output(s) to a simple switch. (If that is indeed the case - sometimes, the drawings oversimplify the signal types.)

gmpartsdirect.com shows the sensor to be about 130 bucks. https://www.gmpartsdirect.com/oem-pa...bC12Ni1nYXM%3D

HTH.

Doug

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post #9 of 13 (permalink) Old 05-03-2019, 11:18 AM Thread Starter
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That sensor you referenced is the correct one (part #15821098 per my local GM dealer). I found a new one on ebay for $40 https://www.ebay.com/itm/AirBag-Side...72.m2749.l2649

What I'm not sure about now is if the rear door would also have a sensor that would need to be installed, since both passenger doors were replaced with different doors. My mechanic didn't say anything about the rear door. Anyone know if the rear door also has a sensor?
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post #10 of 13 (permalink) Old 05-04-2019, 08:47 AM
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Quote:
Originally Posted by PontiacPower View Post
What I'm not sure about now is if the rear door would also have a sensor that would need to be installed, since both passenger doors were replaced with different doors. My mechanic didn't say anything about the rear door. Anyone know if the rear door also has a sensor?
I couldn't find anything. I looked in my computer shop manual and at gmpartsdirect.com , but didn't see anything that indicated a sensor in the rear door.

On a separate note, studying the two schematics I sent, I am puzzled by the 2nd one. It shows just the two sensors, with the same wire colors and pin numbers as the two sensors on the other drawing which also included the side air bags. Looking at all the air bag related drawings in the computer manual, I'm thinking that 2nd schematic was some sort of draft that should not have been included. So you can ignore that one. (And, for sure, it's not for the rear doors - any sensors there would have different pin number assignments at the SDM.)

Sorry about including that bum steer - but I'm blaming it on the manual

<head slap!>BTW, it occurs to me, you still have two good, stock doors on the left, which mirror the right side doors. Any questions about right side sensors and wiring can be resolved by referring to the left side, I would think.

Doug

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Last edited by plano_doug; 05-04-2019 at 09:03 AM.
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post #11 of 13 (permalink) Old 05-04-2019, 09:44 PM Thread Starter
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Thanks Doug. I assumed there would be no sensor in the rear door since there is no airbag in the rear to my knowledge, but wanted to make sure. I had also thought of the fact that I could reference the wiring of the left door, I just was hoping not to have to pull the door panel off of both doors but I will if I have to. I have never pulled off a door panel before so that is something else I have to find info and and learn how to do.

Ken
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post #12 of 13 (permalink) Old 05-06-2019, 06:32 AM
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Quote:
Originally Posted by PontiacPower View Post
Thanks Doug. I assumed there would be no sensor in the rear door since there is no airbag in the rear to my knowledge, but wanted to make sure. I had also thought of the fact that I could reference the wiring of the left door, I just was hoping not to have to pull the door panel off of both doors but I will if I have to. I have never pulled off a door panel before so that is something else I have to find info and and learn how to do.

Ken
Hi, Ken,

On front doors, there's a bezel where you put your hand to pull the door closed. Remove the bezel and then remove the two screws underneath.

There is one screw behind the door release (handle).

After that, there are ~10 plastic push pins that hold the door panel on. It's best to use a trim panel tool on those. You can get one at many places including most auto parts stores.

HTH.
Doug

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post #13 of 13 (permalink) Old 05-06-2019, 02:16 PM Thread Starter
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Quote:
Originally Posted by plano_doug View Post
Hi, Ken,

On front doors, there's a bezel where you put your hand to pull the door closed. Remove the bezel and then remove the two screws underneath.

There is one screw behind the door release (handle).

After that, there are ~10 plastic push pins that hold the door panel on. It's best to use a trim panel tool on those. You can get one at many places including most auto parts stores.

HTH.
Doug

.
OK thanks. I'll give it a go when my busy life allows me some free time
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