Sagging Car Truck or SUV How to Diagnose Air Suspension

We got this vehicle in the shop, and it's riding low. There is an air suspension in it. Something's not working. Let's check it out.

All right, so with the key on, we can see on the dash it says, "Stop, car riding low," which is a good thing. So, that means the module that controls the air ride, or air suspension, knows that it's riding low and there's something wrong.

Next, if you have a scan tool that's capable of monitoring the suspension, let's just see what the computer says, and we're going to read the fault codes. And it actually has a code for the suspension, which is good. You can actually, also, with certain scan tools, you can read the data, and we can go to the level sensors. You want to make sure the level sensors are working properly. Confirm. And that's what the values are right now. We can actually graph them, we can go out and raise the vehicle and see if these go up.

All right, now I'm going to raise this up. And we can see there's a nice, smooth transition on the line, which is exactly what you want. You don't want any spiking or anything. So, we know that level sensor is actually working.

Right here, above the rear differential, you can see where the level sensor is. This is what sends the signal to the computer to tell the pump to kick on or to exhaust the pressure to the rear suspension. It's connected right here at the sway bar. So, if the sway bar broke, for whatever reason, then this wouldn't be working properly.

So, we're in the passenger side underneath the seat in front of where the kick panel is. This is where the module actually is located. Now, when you're diagnosing this, you wouldn't necessarily have to take this down and see this unless you had something wrong with this part of the system.

All right, and from here, this little cover right here comes off. Pull that out, and the fuse is actually right here. This one that's labelled "74," that's the fuse that goes to the pump. So, what you could do is, you could disconnect the connector right here, just like that. To get the fuse out, it's a little bit tricky. I'm sure there's another method to do this, but just take a pick on the top. It's clipped in right there. You can take another pick and just push the fuse up, and it slides out, then you can check the fuse. And this fuse happens to be good, so we can put that back in there. And your fuse may be in a different location, so check your owner's manual. I'll reconnect this, lock it in place.

So, next, we want to access the pump. It's located right here in front of the driver side front tire. And you want to pull that wheel well off so that you can get to the connectors and stuff. These connectors are for the pumps, and then this is for the valve. And to disconnect the connectors, push down on the terminal and pull it out. And lookit, there we go. It's melted right there. It's actually making noise right now. But, yeah, it's melted right there, which is good. So, we found part of the problem. That may not be the whole problem, but at least we're on the right track. It's surprising that that did not cause a fuse to blow, but there's definitely a connection issue there. So, we'll have to make a connection here, see if that pump's working properly, and then see if the airbags hold air.

All right, so what I did was take a jumper harness and make a good connection here to the pump itself, and we're going to test it to see if it works. I already checked for power and ground, and we did have power and ground there. You'd want to use a test light and test those things, but so we're going to test that. Remember that when you're starting the vehicle, you're going to want the rear suspension to be down on the ground. You don't want it to be hanging. Otherwise, it's not going to tell the pump to kick on.

We started the car, and I checked the compressor. I could feel that it was running, but it wasn't building pressure.

So, we replaced the pump, and now the airbags are working properly, but we don't know if there's an actual leak in the lines or the airbags. There's a reason why that connector failed. It could be because the pump was running too long. So, you're going to want to check these lines right here. You can spray some soapy water on the lines. And this line goes into the cab, and then comes to the back of the vehicle. That air line comes out right there near that rubber grommet. So, you could check inside the car as well, see if there's any leaks. You might be able to hear a leak. Some of the best things is just spraying down with soapy water. And there's a junction right here, and if you spray it down with soapy water and you see any bubbles, then you know there's going to be a leak there. I don't see any leaks there, which is good. Also, the airbags themselves, there is covers over these, so you would have to take these covers off and then spray the bag down themselves with soapy water.

So, make sure you check all the components, not just the rear airbags. If you find a leak, chances are your pump might be weak, and vice versa. If your pump is weak, chances are the bags could be leaking.

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