ABS Light

[Big T]

Ever since I bought the ‘99 K2500 Suburban in 2010, the ABS has been an issue. PO had pulled the plug to the ABS pump to avoid the ABS light. I briefly got it working by replacing senders at the bearing hubs. Then it went back into ABS light mode, until a couple episodes where it briefly worked.

This past weekend I replaced rear brake shoes and drums. The results were great. Monday I drove it a mile to talk to the mechanic about the transfer case shifting. The abs light was off and the abs pump worked when I tested the brakes on a patch of pine needles on our driveway. Shut down, talked transfer case with mechanic, restarted to go for a drive and the abs light came back on. Stopped at our house and plugged in my GM Tech II and he was able to pull a code for ABS pump circuit. He said when that happens, it’s typically the ABS fuse in the box under the hood, or the pump is out. I’m now thinking it must be in the ABS wiring, otherwise why would the pump work sometimes? If the pump were bad, it would not work at all.

 

[Big T]

So I ordered a used replacement Transfer Case Control Module (TCCM) which arrived today. I installed it and nothing. No lights on the push buttons to shift the transfer case. So I pulled it and reinstalled the existing and I’m back to it going into 4Hi, but light flashing at the shift button and still no AWD and no 4Lo. Had to push around wiring and plugs to get the upper tab on the TCCM locked in. Big surprise, the ABS light was off on my test drive and the pump was clearly cycling during hard stops on dirt and gravel roads:

I won’t consider this a victory until a month’s worth of on/off cycles. Clearly the pump is working, but I probably have a loose connection somewhere.

 

[dbrannon79]

check all the connectors on the ABS pump. when it was left disconnected for a while, corrosion could have started in ether the giving or receiving end of the connector.

 

[jrsavoie]

So I ordered a used replacement Transfer Case Control Module (TCCM) which arrived today. I installed it and nothing. No lights on the push buttons to shift the transfer case. So I pulled it and reinstalled the existing and I’m back to it going into 4Hi, but light flashing at the shift button and still no AWD and no 4Lo. Had to push around wiring and plugs to get the upper tab on the TCCM locked in. Big surprise, the ABS light was off on my test drive and the pump was clearly cycling during hard stops on dirt and gravel roads:

I won’t consider this a victory until a month’s worth of on/off cycles. Clearly the pump is working, but I probably have a loose connection somewhere.

I've been accused of having a loose connection my damn self.

 

[Big T]

First start, as soon as I start rolling, the ABS light came on. Drove over 500 miles from Stevensville, Montana to Salt Lake City. Current watching Cal at Utah from seats on the 50.

 

[Big T]

95+% of the time the ABS light is on, there there are those times it is not on and everything works perfectly:

 

[dbrannon79]

There has got to be a bad connection somewhere. enough so it sends the wrong signal to the ECM to set a code. have you been able to hook up to it and read what the code is ?

 

[MrMarty51]

Many times a bad connection between a wheel sensor and the module.

 

[Big T]

There has got to be a bad connection somewhere. enough so it sends the wrong signal to the ECM to set a code. have you been able to hook up to it and read what the code is ?

We did hook it up to my Tech II in Montana and it provided a code for pump motor circuit (did not take down the number). My mechanic said that code usually points towards the ABS fuse (it was fine) or the pump itself being out. Well, clearly the ABS pump is not out.

I am still learning how to use the Tech II. I left the Tech II up in Montana and the Truck is down in Fullerton, but it will come down, along with OEM encoder motor and the ordered shift position sensor, with my wife on her trip down for Thanksgiving.

 

[Big T]

Many times a bad connection between a wheel sensor and the module.

I will check the wheel sensors, as I have experienced that before.

 

[Big T]

This video pretty much describes the issues I've been facing with the ABS light coming on. However, since I redid the rear brakes in September, I have had several events where the light has not come on and the ABS works as intended, while for 10+ years the light just came on when I started rolling. Concerning part is that the ECBM and BPMV are specific to K Series and even specific to 6.5 diesel version and are no longer available. Need my Tech 2 down in Fullerton to start in on this. Best hope is it's just due to grounds.