Paccar KW, PB T/S VCAN, VCAN1, VCAN2

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campbell.kwtech
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Paccar KW, PB T/S VCAN, VCAN1, VCAN2

Post by campbell.kwtech »

‡Revised June 18, 2022.

The information here in relates to the KW T680 and PB 579. In general, the information applies to other models as well, but the specific Harness checks and controllers are on the previously mentioned.

These CAN's are checked more often than any of the other CAN's, mainly due to the all the modules communicating on these CAN's. The second most checked CAN would most certainly be the A-CAN. Watch for future posts on the A-CAN, F-CAN, and the proprietary ABS CAN.

READ my post for CAN 101 Paccar KW PB before continuing to read this post.

‡Create all the diagnostic reports as possible, i.e. Engine, transmission, ABS, Wingman, Fusion Camera, Safety Direct Processor, ESA Tool. Connect to all the modules, save the diagnostic reports, review all the reports, look for a commonality with the fault codes when comparing to the other reports. The best reports would be the Bendix ACOM or ACOM PRO "if there's a Bendix ABS module". ACOM PRO is best due to ACOM PRO will connect to all the modules and make one report, and Acom Pro has a CAN DATA BUS monitoring feature.

The Bendix ABS logs CAN faults and events much sooner than the other modules. Eaton Service Ranger also generates a very informative report which needs to be compared to the Bendix and engine report.

Intermittent CAN faults are certainly the most difficult when trying to diagnose the root cause.
These reports can indicate if the entire CAN is going corrupt or if it's just one device dropping out. If the case is the whole CAN going corrupt, you're still burdened with isolating the suspect module or the area of the physical layer. It would not be usual for the Eaton TECU "NOT" to log CAN faults if the CAN leg (away from the backbone) has an intermittent CAN connection, (broken CAN wire), (I have not seen this with an Endurant Transmission or Paccar Transmission as of yet).

Trouble shooting VCAN, or VCAN1 and VCAN2: All Picoscope testing is done at the 9 pin
diagnostic connector.

Once you have verified that the customer has not connected a device to the 9 pin diagnostics connector and has not tucked the OEM 9 pin connector up in the dash, and the customer has not connected/spliced into any of the CAN wiring on the 9 pin diagnostic connector, and: If all the preliminary CAN checks prove to have checked good, I then would continue to first use "Nexiq device tester" on all 3 CAN's at the 9 pin diag connector before connecting Picoscope.

Scroll down for more on "using Nexiq device tester".

If the diagnostic reports indicate the problem to be a CAN communication issue to the transmission (CAN dropping out):
Place the Eaton TECU in PD diagnostic mode for trouble shooting. While in PD mode, the transmission TECU is now in a heightened sensitivity state for fault detection. Move the CAN wiring at the firewall area. It would not be unusual for the Eaton TECU module to detect a CAN fault in "PD mode" when moving the harness due to the heightened sensitivity state and "NOT" having logged a fault prior to the truck arriving to the shop.

In this case, the diagnostic reports would indicate all the other modules are logging CAN communication faults with the Transmission and the trans may not have logged any faults yet due to the problem may have started recently, which could be the CAN wiring is broken after (away from) the backbone. After the problem has been present for a awhile, the transmission starts logging faults.

Repairing the CAN to the transmission.
Paccar makes a CAN extension harness, the following parts can be used to overlay the CAN to the Eaton transmission TECU without cutting existing CAN wiring, excludes Endurant and Paccar Transmission due to the connector type.

Parts needed:
(1) P92-2785-01600 Can extension harness, (2) 2 pin Amp connectors wrapped in Coroplast harness tape.

(2) CN24680 Small Deutsch terminal socket, (female terminal pins). Gold plated.

Remove the 3 pin Deutsch female receptacle connector from harness P92-2785-01600. Cut off the two terminal pins, trim off about 1 to 2 inches of harness tape, crimp on the smaller 2 Deutsch terminal socket pins using the Deutsch closed barrel crimper.

Testing the CAN wiring with Picoscope.
Connect Picoscope and monitor the waveform and move the harness as before, checking for transmission CAN drop out. Picoscope is thousands of times faster than Eaton Transmission PD mode, and you can see voltage spikes in amplitude and interruptions in the waveform as a bad connection occurs.

Using Nexiq device tester at the 9 pin diagnostic connector:
Pins C & D is Channel 1, pins H & J (DCAN) is channel 2, and pins F & G is channel 3.

Sometimes Channel 2 will not show any CAN traffic unless ESA Tool or Davie Tool is connected and active. Model Year SPECIFIC.

After selecting USB 2, and J1939 with the desired channel, click start, check the baud rate at the bottom, is it correct? Are there any Source addresses showing up? Is Data flowing or is it flowing the words "error", if source addresses are showing up and raw data is flowing, click CAN statistics soft button, this screen will show CAN error message counts. Are all the source addresses that are being displayed present for all the known devices on that CAN?

Now keep in mind, Nexiq device tester may appear to show no problems, you have to take in consideration what is actually appearing on the dash like gear display, warning lights, as well as what you see with Nexiq device tester. Nexiq device tester doesn't always show problems like a disconnected device or open backbone or the device that is corrupting the CAN. One problem with Nexiq device tester is when viewing the source addresses, if a device drops off the CAN, Nexiq device tester will not update showing the device had dropped off, it continues to show the device to still be present. However, Nexiq device tester does update as devices are starting to connect to the CAN and send messages as the key is switched on or as devices are connected to the CAN.

After verifying (or maybe not) if CAN issues are present with Nexiq device tester, I'll continue with connecting Picoscope to monitor CAN activity and Network errors after taking into consideration all the observations that were previously made. It's so easy to over look the obvious, like confirming the PRELIMINARY CAN CHECKS, (CAN resistance, voltages, shorts to ground.

When referring to VCAN, reference pre EPA 2016. At the (Black) 9 pin diag connector, pin C =
CAN Hi, pin D = CAN Low. Pins F & G is J1587/J1708 databus.

When referring to VCAN, reference EPA 2016. At the (Light Green) 9 pin diag connector, pins F
= CAN Hi, pin G = CAN Low, this is a 250 kb CAN.
O-CAN pins are: pin C= CAN Hi, pin D= CAN low, this is a 500 kb CAN.

Sometimes these connectors can be Lime Green in color.

When referring to VCAN1, reference MY2018 beginning 2nd week of October 2018. At the (Lime Green) 9 pin diag connector, pins F = CAN Hi, pin G = CAN Low, this is a 250 kb CAN. Note, there were a very small group of chassis that were manufactured in April of 2018 that were CVMUX.

VCAN2 pins are: Pin C= CAN Hi, pin D= CAN low, this is still 500 kb CAN. This was called "O" CAN "proprietary" CAN on the EPA16.

Sometimes these connectors can be Light Green in color.

Next Gen models with the digital dash. Pin out for VCAN2 stays the same from MY2018,

VCAN1 also stays the same on pin F = CAN Hi, pin G = CAN low, but is now 500 kb.

All the CAN's mentioned begin and end at the the Cab Controller (CECU) or (VECU) and the Engine ECM (PMCI, PCI, PCI2). Model Year SPECIFIC, reference diagrams for terminating resistors locations.

Connect Picoscope at the 9 pin diag connector, if Picoscope proves a poor waveform is present, continue to isolate the cab from the chassis.

With Picoscope connected to the 9 pin diag connector, Disconnect the engine harness from the I.P harness at the firewall, then turn the key on, if the CAN is still corrupt, continue checking for the problem in the cab. You may want to add a 120 resistor to the CAN pins at the I.P.firewall connector. Is the CAN still corrupt after disconnecting the engine harness from the I.P. harness?

NO, THE VCAN (1)(2) IS LONGER CORRUPT AFTER DISCONNECTING THE ENGINE
HARNESS FROM THE I.P. HARNESS, SCROLL DOWN TO (**).

Yes, VCAN (1),(2) IS STILL CORRUPT AFTER DISCONNECTING THE ENGINE HARNESS
FROM THE I.P. HARNESS.
Continue to monitor with Picoscope. And continue checking inside the cab.
Now disconnect the roof harness from the I.P. harness, this connector is behind the glove box, and to the right, near the bulkhead. There are 2 connectors for the roof harness. The CAN is on one connector. Add jumpers to the CAN terminal pins at the I.P. harness connector where the CAN comes out of the I.P. harness connector and back in, (the CAN backbone loops in and out of the Roof Harness and back into the I.P. harness). Reference the I.P. harness diagram for connector CAN pin out identification.

Is the CAN still corrupt after disconnecting the roof harness?
If yes, scroll down to (*).

If not, continue below.
NO, VCAN (1),(2) IS NO LONGER CORRUPT AFTER DISCONNECTING THE ROOF
HARNESS.
It appears the problem is in the roof harness. Reconnect the roof harness to the I.P. harness and continue to monitor Picoscope while removing devices one at a time, like the LDWS camera, (i.e. Fusion, Takata), Remote Diagnostic Module, The Safety Direct Processor (SDP) or some other CAN device which may be connected to the CAN on the roof harness, disconnect them one at a time from the roof harness while monitoring Picoscope, inspect the roof harness for chafing.

*-YES, THE CAN IS STILL CORRUPT AFTER DISCONNECTING THE ROOF HARNESS.
Apparently the problem is in the I.P harness. Continue with checking the I.P. harness.
If after disconnecting the Roof Harness and the CAN is still corrupt, then remove the instrument cluster, Look in behind the instrument cluster, directly in front of the cluster, on top of the I.P. harness is a 2 Pin Amp connector which is VCAN, OR (V-1) OR (V-2) (Model Year SPECIFIC).

Check for a device plugged into this connection and isolate the device, (sometimes a CAN device is connected at this location). Continue with unplugging modules one at a time from the I.P. harness, (CECU, VECU, ABS, PCC, or a customers device) while monitoring Picoscope.

Below: Trouble shooting continuation after disconnecting the engine harness.

**- NO, THE VCAN (V-1)_(V-2) IS NO LONGER CORRUPT AFTER DISCONNECTING THE
ENGINE HARNESS FROM THE I.P. HARNESS.
The problem appears to be isolated outside of the Cab.
Reconnect the Engine harness to the I.P. firewall connection. Focus on the VCAN, (V-1)_(V-2) on the outside of the cab. This CAN will include the Engine ECM, and possibly a Engine Fan control module. The chassis may also have the following: a Forward Looking Radar (Wingman, Onguard), Tire Pressure Monitoring System, Eaton Autoshift/Ultra Shift/Advantage/Endurant, or Paccar Transmission and these devices are connected to the VCAN backbone at the left rear of the eng. Try and identify these separate legs of the CAN to their perspective devices. These CAN legs loop in to the Main chassis harness and to their devices. The CAN backbone is extended going to the chassis harness and the leg continues to the rear to the Transmission,
usually at the firewall area.

The CAN backbone going to the forward looking radar also loops into the Main chassis harness then going forward in the left hand frame rail, the same for the TPMS.

Most common problems with VCAN (V-1) (V-2), on the outside of the cab includes broken CAN wiring to the Transmission usually after the backbone extension as the leg enters the main chassis harness. But this failure is usually accompanied with Transmission fault codes and related faults in the engine and ABS modules.

Other areas of VCAN issues on the outside of the cab are rubbed CAN wiring to the forward looking radar and TPMS. But these issues will usually have related fault codes. TAKE NOTE: if the TPMS has lost its ground input (a broken ground circuit) to the TPMS module, the TPMS will try and ground through the CAN and corrupt the CAN. Also corroded connectors to these same devices will corrupt the CAN.

Rare to see but possibly, is the Forward looking radar with the wrong baud rate.
Last edited by campbell.kwtech on Sat Jun 18, 2022 2:52 pm, edited 2 times in total.

Steve Smith
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Re: Paccar KW, PB T/S VCAN, VCAN1, VCAN2

Post by Steve Smith »

Hello and thank you so much for taking the time to post this information

The tip you gave regarding.......

"One problem with Nexiq device tester is when viewing the source addresses, if a device drops off the CAN, Nexiq device tester will not update showing the device had dropped off, it continues to show the device to still be present. However, Nexiq device tester does update as devices are starting to connect to the CAN and send messages as the key is switched on or as devices are connected to the CAN."

is a piece of diagnostic GOLD and will not doubt carry across to other serial tools

Such information can save you hours and tears too.

Thank you again, take care......Steve

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campbell.kwtech
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Re: Paccar KW, PB T/S VCAN, VCAN1, VCAN2

Post by campbell.kwtech »

thank you for the feed back Steve!

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Re: Paccar KW, PB T/S VCAN, VCAN1, VCAN2

Post by innocentbystander »

What a great wealth of info!

What do you know about VCAN3? On H and J.
I have a MY2018- September listed as a 2019, Kenworth T800 with a Cummins. This truck seems odd to me as it is this late and still has CECU3-NAMUX3, chassis node and NO VECU and has 3 can lines. Devise tester reads connects to all modules, Jpro recegonizes CECU3 however ESA refuses to connect to anything. Good voltage and ohms across all can lines except C an D showing 60 ohms but D to ground showing 1.6-1.7 volts. C to ground shows good about 2.6. The best I can figure ESA communicates on CAN1 (F&G) and CAN3 (H&J)

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Re: Paccar KW, PB T/S VCAN, VCAN1, VCAN2

Post by innocentbystander »

campbell.kwtech I received your PM, However I am not authorized to send PMs even as a reply to yours. My post disappeared because I edited it to update the truck info and the post was sent back to mods for approval.

Looking forward to your reply.

Thanks

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Re: Paccar KW, PB T/S VCAN, VCAN1, VCAN2

Post by campbell.kwtech »

Hi innocentbystander,
To address your questions:

Pins H & J is the "D" CAN, there is no VCAN3. ESA TOOL communicates only with the CECU on the "D" CAN.

Pins F & G is called V-CAN. Pins C & D is the O-CAN. Reference EPA 16 OBD.

Build date and model is everything on every job I work on.

Nothing odd about your truck. The T800 didn't come with a VECU.

Side note, concerning the T680, nothing odd if your truck was built prior to the first week of October 2018. Although with that said, there were a handful of trucks, maybe 5, built in April of 2018 that are CVMUX.

I believe your truck is a EPA-16 concerning the 9 pin.

Nothing odd about the voltages on C & D, this is a 500 kb direct connection between the 9 pin and the engine. Those voltage readings are plausible.

I can only assume that your only issue at hand with this truck is that ESA TOOL will not connect. I can only assume you tried to connect to another truck with ESA TOOL and it connects.

If this is the case, I would recheck the DCAN at the 9 Pin Diagnostic connector pins H & J. Do you have 60 ohms with key off door closed? If so, check short to ground, black lead on ground pin A, and red lead on pin H then pin J. This reading could be as low as 3600k ohm.

Then Open the door and check voltages on pins H and J, they may or may not be equal in voltage. Voltage could be anywhere at 1.5 to 2.5 volts.

If the resistance readings and or voltages are not as expected, perform pin to pin resistance checks on the D CAN between the 9 Pin
Diagnostic Connector and the CECU connector.

A warning concerning testing the CECU connector pins. These are .5 mm diameter square pin. You can easily damage the connector pins by inserting the wrong test pin.

Close the door. The key is still in the off position.

Open ESA TOOL, before clicking connect, open Nexiq Device Tester and select USB2, J1939 channel 2 and click start, and click on CAN error button. Position these windows Side by side so that both windows can be monitored. Now go to the ESA TOOL window, open the door, switch the key to the ignition position and click connect, without delay click on the Nexiq Device window. Now you can monitor with Nexiq Device Tester CAN addresses and CAN errors while connecting ESA TOOL, the CECU source address 49 should show up.

If everything checks out right, I would suspect that your issue is ESA TOOL needs to be uninstalled and reinstalled, but if ESA TOOL connects to another truck then don't uninstall ESA TOOL.

ESA TOOL only connects to the CECU on the DCAN.

You'll need a Y adapter to connect to the ABS with Bendix Acom or Meritor Tool box.

The engine will connect with or without the Y Adapter using Cummins Insite.

When using Nexiq Device Tester with no Y ADAPTER, select channel 3 to view VCAN source addresses (pins F & G).

Hopefully this will help you out.

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Re: Paccar KW, PB T/S VCAN, VCAN1, VCAN2

Post by innocentbystander »

campbell.kwtech Thank you for your time and info, I knew that D-CAN was H and J but was confused by no mention of it in your post about EPA 2016+ but now I understand about all 3 cans. However to confuse matters even more I had a 02/14/2018 T880 in the shop and ESA connected to it and it did not even have a pin in the H Terminal and had 12 volts on the J terminal! ???


But back to the T800, Devise tester will connect to all modules on "channel 1 and 3 but errors out on channel 2. I have not tried it as you described while connecting ESA but will Monday.
I am suspect that my channel 2 in my USB link has died, I have a new one going to try Monday also.

The original fault with the truck is random brake lights on, even with the brake light switch disconnected. at times the brake lights will come on when you open the driver door, seems at the same time the display boots up by the door opening. Turn the truck off, close the door, come back later and brake lights work normally, then after a few minutes go back to randomly staying on or coming on when door open/display comes on. My first thought after going through switch/wiring etc, was to reflash with latest software and monitor CECU but if not have you seen this before or have an Idea what the problem is?

Thanks again!

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Re: Paccar KW, PB T/S VCAN, VCAN1, VCAN2

Post by campbell.kwtech »

I'm going to send you a private message to respond to your latest post.

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