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Discussion Starter #1
I have the quite well known issue with 4WD Service light coming on, along with several other error lights in the dash. Also the ABS starts pulsating every now and then (when not supposed to).

As I understand it, the most likely issue is that one of the ABS sensors are bad.

While the error lights were lit up, I tried to get the DTC code to determine which wheel it is for, but no codes showed up. If the issue is the ABS sensor should there have been a DTC code? Or is that not always working?

I believe I also heard that it usually is the front right sensor that fails, maybe I should just replace that to start with.....

Any ideas on how to determine which sensor is bad?
 

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OBDII is a Government Mandated System on all cars, that is what will report DTC codes easily accessible to the owners and independent shops. i.e. codes you can get doing the key dance or using an inexpensive OBDII scanner.


OBDII is only for emissions (pollution) and thus only the DTC's/codes effecting emissions are part of it. Just about everything with the engine and some of the codes for the Transmission effects emissions. Things like body/chassis/ABS/Air Bags, etc do NOT effect emissions.


So guess what all the manufacturers do? They make only the DTC's available for what the Government mandates and the rest they make extremely difficult to access without a proprietary protocol that they keep from everyone else. Thus they force folks into their dealerships to pay for these services.


Some of the larger independent shops may have invested in the tools that can read the ABS codes. A tool to do it yourself will cost at least $550 and that is a bottom line one that you have to provide the laptop and is NOT very good. They can't do everything the Dealer Tools can, but certainly enough to avoid going to the dealer for basic diagnostics.


Or you can take it the dealer and pay your 1 hour of labor (a few good dealers will only charge 1/2 hour) and wait in the waiting room 2 hours, to have them plugged the tool into your vehicle for 5 minutes and read out the codes to you.


Yes, one or two of the OBDII scan tools advertise they can read ABS and Air Bags, its iffy because the protocols and codes for ABS and Air Bags change over the years and between the manufacturers, and thus most of those tools can only read 50%-75% of the cars on the road, which you won't find out for sure until after you buy it. As well, they cost just short of the cheapest tools that can read everything one particular Manufacturer makes.
 

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I posted in the thread asking him how he got it.


The manufacturers sometimes do include a few extra codes over top of OBDII, but definitely NOT all of them.

Are you performing the Key Dance successfully? If you are, you would get a message in the EVIC stating there are NO codes, or "End of Report" if you were. The Key Dance is easy to screw up, most people don't get it right the first dozen times they try, watching the youtube video helps. So its possible, you thought you did the Key Dance properly and since nothing happened you assumed you didn't have any codes, in reality you did it wrong and never got the codes to spit out. Getting the message in the EVIC indicating the DTC report has ended is the key to telling if you did it correctly.

As well, you may have a different problem and codes than what was in the other thread. That guy was lucky, his problem's DTC got included with the Mandated OBDII DTC's that the GOV makes the manufacturers provide the owners easily. You're unlucky, in the fact what ever DTC you have, did NOT get included with the Mandated OBDII codes, and thus can't read them without the expense or hassle.

Regardless, if you have a "4WD Service" you have stored DTC's, its just the Key Dance will NOT spit them out like the other codes for the Engine and a few for Transmission and Drivetrain, that can effect emissions. The manufacturer may have included a few more, but there is still a lot of codes the manufacturer keeps from you.

BTW, "the ABS starts pulsating every now and then (when not supposed to)" can happen with a perfectly good working ABS system. Do you have ABS Warning Lights on in the Dash? If you do NOT have an ABS Warning Lamp on the Dash, likely you do NOT have any ABS codes, or at least NO ABS codes important enough to effect ABS performance and vehicle safety.

Do you have oversized tires on the vehicle? That throws off the RPM relationship and can activate the ABS at improper times. It can be corrected by having the new tire diameter programmed into the correct model handling the traction control and ABS.
Do you understand fully how the ABS/Tract Control/ESP/Roll Mitigation/Wheel Slip Limiting, etc all work for the Commander? No longer does the ABS module simply operate to prevent wheels locking up while braking, it operates all the time to maintain wheel traction if a wheel slips in mud/snow/ice. It will activate if you go around a turn to fast to try to prevent roll over, etc,. If it sense your about to fish tail or spin out, the ABS activates to prevent it, etc. So there are a lot of people that don't understand fully how the systems on their vehicles work and think something is wrong because the ABS activated, when in reality the ABS was doing exactly what it is suppose to do, the driver just didn't know what its suppose to do.
Believe me if you're driving up a hill in mud or wet grass, your ABS will be going off every few seconds, and it is suppose to, in order to keep your wheels from spinning and losing traction. Even driving over level ground in snow/ice/mud/wet grass (i.e. low traction conditions) will activate ABS without ever touching the brake pedal.

Finally, you've got a "Service 4WD" warning light, BUT do NOT have an ABS Warning Light, I think you're jumping to conclusion thinking its a Wheel Speed Sensor.

There are multiple threads on the Service 4WD light, how a software update can cause it erroneously, and how a subsequent even later software update can fix it. The fact a Transfer Case shift motor or Final Drive Control Module failing can cause it as well (indicating a real problem that needs to be fixed) and is a common failure on the Commander.
 

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Discussion Starter #5
I have the ABS, ESP BAS, Stability system (car swerving) and the "Service 4WD system" in the RPM window. But no DTC code.

But like you said, maybe the issue is something else....
 

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I have gotten the ABS/ESP/BAS/Traction Control warning lights in the Dash for a blown fuse. I had no DTC's, but I also had a tool that could read all the DTC's from all the modules. And it gave me multiple codes for failed communications between the steering wheel sensors and the control modules. The fuse for the control module in the steering wheel was blown. I also had the air bag warning light, also for a blown fuse. They were unrelated.


The 4WD Service light could be unrelated tot eh ABS/ESP/BAS/Traction Control warning lights.


In my case, I had replaced the AC evaporator myself, requiring me to remove the entire dash. At one point, I had turned on the ignition while most of the wiring was still disconnected, I think that caused blown fuses to the Steering wheel.


There are several fuse boxes, two under the hood and one under the dash. It was the fuse box under the dash that had the blown fuses for me. You have to flip down the plastic trim panel at the bottom of the driver side of the dash to help see the fuse box, as well as open the door or remove the plastic cover on the underside of that side of the dash.
 
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