2010 cascadia w/DD15 New active fault code

The code is for the left rear modulator valve open. How good are you with a multimeter? The issue could either be (from most likely to least)
1. The wiring from the modulator valvet to the ABS ECU
2. The modulator valve could be open
3. The ABS ECU may be faulty (most likely not the issue)

 

SID 9 and FMI 5 is the left rear modulator valve has an open circuit. Could be a wiring issue wire or in the modulator itself. Check the connections and ohm out the modulator. If the modulator ohms out good. Ohm it out again at the ECU to test the wiring. I'm not sure if you have Bendix or Wabco ABS. Both have manuals online to give the the troubleshooting for that code.

 

It's not in the wheel. The sensor in on the axle, but that is not a sensor code. Follow the service airline from the brake chamber, it goes to the modulator valve. It'll have a electrical connector with 3 pins in it. The modulator needs to be tested, if it's OK, then wiring needs to be tested. If there is nothing wrong with either of them, then the ECU could be faulty, but as already mentioned, the ECU is usually not the cause. The most common failure is wiring, second most common would be the modulator.

 

Just piggybacking off what grape ape said. I would disconnect the modulator valve (under the 5th wheel). It is the left side valve that has a circle plug. Ohm pins 1 and 3 on the valve itself. Should be between 3 and 10 ohms, plus or minus a few ohms. If that is good, plug it back in. Then I would remove the lower panel of the dash, disconnect connector X2 on the abs ecu. ohm pins 2 and 5 at the harness, and that should match the reading at the modulator valve. If it doesnt, that will indicate an open wire between the abs ecu and the modulator valve. Dont worry about any connections at the hub, as that would throw a fault code for the wheel speed sensor.

 

All that is saying you have wabco abs, which is the most common on a freightliner platform

 

You're welcome. Did you get it figured out?