Wabco ABS issues

I am working on a 2008 sterling tandem axle snow plough/ salter truck with mercedees engine and a wabco abs system. I had a abs light on so I scanned codes and found 8 brake trouble codes. The codes were listing front right, rear left, and rear right sensor faults, The scanner I use does not time stamp so I am unsure when the codes have appeared. I did have 2 active codes
1. spn 802 fmi 4 other components voltage supply axles 1+2+dif, low voltage/open circuit
2. spn 792 fmi 5 wheel sensor right rear open circuit.

I cleared codes but the wheel speed code came back. I brought up abs sensor speed live data and went for a drive. All 4 sensors were reading accurate speeds. Even when the wheel speed sensor code was active it was still reading proper which I find odd for a sensor open circuit code. I would clear the codes during the drive and the within a few seconds one or the other listed codes would become active but never did they go active at the same time.

I have not done any diagnosis yet as my shift ended shortly after I got back so I will continue Monday. I am suspisous that the abs ecu is possibly shorting out again due to the aluminum becoming porus and salt getting inside. I have replaced the ecu a few years ago due to this reason and when it failed it started throwing many different codes similar to what is happening. I will be checking batteries, and fuses first thing Monday and possibly find my abs ecm power feed and check it for constant voltage. I find it strange how open sensor can still read speed and when ecu power voltage low code the wheel sensors still read fine. Any help is appreciated and I will provide more info on Monday.

 

Thanks Hulld I totally agree with the salt causing conductive issues. I have been a municipal mechanic maintaining a fleet of 14 salt/plow trucks for about 12 years. I will check the plugs and report back on Monday.

 

Well here is update a few days late. Monday morning I inspected the abs ecm and found a wire with visual green death at a spot close to the connector. A schematic showed it was one of the ign power wires which would explain the low voltage to abs ecm code. I orderer new deutsch plugs and wire terminals to repin. Once that's done I will move on to the speed sensor issue.

 

Al mechanic you might have better results starting a new thread to get more views rather then piggyback on mine. In any case is it a wabco system? Reason I ask is not knowing your area the wabco ecms are aluminum housings and are a lot of the time mounted under the truck. I have had a few where the aluminum has gone so porus from road salt that water will enter the ecm and fry the boards. This can cause all sorts of ghost codes that come and go with no reason, or codes that seem un repairable. I had one ironically on the same truck a couple years ago that was melting down and shorting out the j1939 circuit and caused the instrument cluster to act erractcally and loose power. Only reason I figured out it was the abs ecm was I decided diagnose the abs code to take a sanity break from the cluster issue not realizing the two problems were connected. I unplugged the abs ecm and the cluster started working!
Point is if the ecm is frying it can be very hard to diagnose unless you have another one to try in its place.

 

Final update I replaced all three abs ecm connectors and both my codes have gone. There was infact 2 wires with bad spots in them. Thank you for suggestions.