ABS trailer code 520216 31 P4 New...

Russell Thornley 13 posts since Nov 20, 2018
ABS trailer code 520216 31 P4 New Cascadia Jul 2, 2020 9:36 PM
We have been receiving multiple ABS complaints on newer P4 new Cascadia's for trailer ABS. The reoccurring code that every truck is having is 520216 31, ESC function is reduced (trailer ABS not OK) condition
exists. Wabco info is short and sweet, saying faulty ABS functionality. Trucks have ranged from 19k, 41k
miles etc and upwards. Operators that pull multiple/different trailers have come in, not specific to a truck with
same route/trailer. Two trucks in question, also present with the 629-11 code, are really new P4's too, (19,805
miles) and these two units happen to have a seven way cord that does not ground to the cab back wall. Instead
routes under the headache rack, under the left side cab and grounds to a frame stud. Ground load tests from
the seven way cord end have always been successful, and no other problems like dirty frame connections. This
520216 does not effect truck ABS but the display does not tell the driver that, they perceive that they have a
truck ABS problem instead, often times dropping the current trailer and bringing to the shop.
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Michael Palumbo 1,380 posts since Nov 13, 2014
Re: ABS trailer code 520216 31 P4 New Cascadia Jul 2, 2020 10:24 PM
You probably already seen HAVE A 2020 P4 COMPLAINT IS THAT TRACTION CONTROL LIGHT COMES
ON , WHEELS GET STUCK HAVE TO CYCLE KEY TO GET WHEELS TO MOVE It's mainly others agreeing
on the ground issue.
If not the ground then the circuit that the PLC signal piggybacks on? A serial number would help define that
circuit. I want to say it is 45?
The trucks ABS ECU talks to the trailers ECU through the PLC filter that is built into the VPDM. I'm not sure
how to test a PLC but you could check the terminals for proper crimping and drag tension.

Jon Cecil 790 posts since Nov 25, 2014
Re: ABS trailer code 520216 31 P4 New Cascadia Jul 3, 2020 12:12 AM

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ABS trailer code 520216 31 P4 New...

SS 1033950 New Cascadia - Trailer Receptacle - Back Wall Grounding Stud
This SS addresses the code you are having. I understand the grounding for the 7 way is different on your unit. I
wonder if the ground is still attached to the back wall on the 7 way. A VIN would definitely help.

Kyle Siebert 3,927 posts since Nov 14, 2014
Re: ABS trailer code 520216 31 P4 New Cascadia Jul 5, 2020 4:48 PM
EDIT 7/5/2020 Kyle: Added parts in quotes.
The PLC filter feeds power to Trailer ABS and trailer pulses this to indicate faults. “ThIs battery
power is also fed to the ABS ECU.” The abs ecu is able to detect these pulses and indicate a
trailer abs issue. So yeah, bad trailer ground will cause this as we all know. But I had one the
other day the BCA power feed cable was loose at batteries, had many counts for smart gear box
codes and trailer ABS 520216/31. So, basically if the power feed is interrupted by; a actual trailer
ABS fault, poor trailer ground feed, or ABS ECU power feed (two of them), it will cause these
faults. Inspect the VPDM for loose connectors or drag test ABS battery terminals, trailer feed
terminals, this power for trailer abs comes over to driver lower a- pillar, I believe. Maybe check
BCA feed cable, fuses and outputs, VPDM positive cables for issues, fuses and relay if it has it.
Mine also had the trailer ground to the left frame rail. Could be a 7 way trailer cable too...

James McFadden 140 posts since Dec 9, 2014
Re: ABS trailer code 520216 31 P4 New Cascadia Jul 8, 2020 2:49 PM
have you had any issues with it kicking out cruse control due to it being an abs problem ? have a unit in now
with this code and customer complaint of intermittent cruse problems . all switches are working normal and see
no issue to why CC would not work. .

Russell Thornley 13 posts since Nov 20, 2018
Re: ABS trailer code 520216 31 P4 New Cascadia Jul 9, 2020 4:08 PM
Between ideas on this thread (thanks for all helpful info), Wabco and CSC tech help, checked battery
connections, all were ok. Checked torque and then removed and cleaned the mgjb grounds at left front firewall,
they were so so but don't think the issue. Did the same at both sides of BCA connections. Drag tested the ABS
pins, then ohmed and then ended up load testing the pwrs, ground and ignition circuits to the ABS module, was
able to get 16+ amps through each circuit without issue. Also checked for loose or damaged vpdm backside
pins on the back side by wiggling the circuits while doing the load test and nothing dropped out like I have seen
in past instances when was a damaged pin. CSC suggested re-flashing the ABS module at that point, we did
and the customer had to take truck to make a delivery. He didn't make it 25 miles before the complaint returned
and the truck was bobtail, however I have not seen it back in my shop to confirm certainly that it's the same
codes yet. I suggested what was mentioned here to Wabco and CSC about a PLC issue. CSC advised I put
an ABS module on it next. Im sorry, the customer had not mentioned a cruise issue with or without complaint,

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ABS trailer code 520216 31 P4 New...

but this is a local truck that makes deliveries in the next valley, don't know how much they use cruise. Forgot to
mention VIN#MJ8950, only 20k miles.

Mark Walstead 21 posts since Apr 30, 2018
Re: ABS trailer code 520216 31 P4 New Cascadia Sep 28, 2020 8:55 PM
VIN- MG0823
miles- 21046
I have the same issue with this truck. Customer complaint of intermittent ABS light, cruise drops out. I have
inactive SPN 520216 FMI 31 logged 125x and SPN 629 FMI 11 logged 29x. I checked the Vpdm, BCA, ground
at the frame, etc. and all looks good. As everyone has already mentioned, SS1033950 would not apply as the
7 way receptacle runs under the left side of the cab as shown in G66-11723-00x.
Russell Thornley, I am curious if the ABS ECU corrected the problem? I have never been able to get WABCO
to commit to an ECU unless SPN 629 is the only fault and everything else has been repaired.
Has any body had a verified successful repair with this issue? I noticed something not mentioned in any of
the talk aside from possibly a bad 7 way cable. I have seen this issue before when customer would replace
the primary receptacle with the incorrect type and trailer lighting problems would occur. Is it possible we are
overthinking this just because it is a P4? I took the primary receptacle off the back of the cab and now I am
thinking it was not tight. When I first went to take it off, I felt on the inside of the plate to see if there were nuts
on the other side or rivet nuts. I don't remember the bolt sticking through the back side of the bracket. When I
inspect the primary receptacle and the trailer cord, it doesn't look like they are making full contact as seen by
the wear patterns.
I can't say for certain as all ABS faults are inactive when it came in, and I was just checking things over. this is
a local run truck, so I'm sure they will be back if this didn't correct the issue.

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Kyle Siebert 3,927 posts since Nov 14, 2014
Re: ABS trailer code 520216 31 P4 New Cascadia Sep 29, 2020 12:04 AM
I did mention a bad 7 way cable. I do think that is likely your issue. Anything that will interrupt the power trailer
power or ground feed to the 7 way or ABS ECU igntion circuit can cause this. I believe both circuits (trailer
power and ABS ECU igntion) come out of the VPDM, and the PLC filter is inside the VPDM.

Mark Walstead 21 posts since Apr 30, 2018
Re: ABS trailer code 520216 31 P4 New Cascadia Sep 29, 2020 11:19 AM
Thanks for the info Kyle. I saw where the PLC filter was mentioned a few times, didn't see it in the schematic. I
didn't realize it is part of the vPDM. That would make sense as the trailer ignition is from the vPDM
Thank you,
01001101 01100001 01110010 01101011
Mark Walstead
Express Assessment Team Leader
Excel Truck Group
Chesapeake, VA
757-424-3000

Kyle Siebert 3,927 posts since Nov 14, 2014
Re: ABS trailer code 520216 31 P4 New Cascadia Sep 29, 2020 4:06 PM
When you understand how something works, it makes it a lot easier to fix.
Some of these solutions are a band aid addressing one of the issues that causes failure. We’re
it should be explaining how the system works and explaining why a certain common issue will
cause the failure.

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