|Vehicle details:||Gleaner Combine Harvester|
|Author:||Tony Nott of Michaels Moama Australia|
Recently I was in a remote part of NSW here in Australia taking some time to look at a JCB Fastrac that the customer owned. It's currently harvest here in Australia and whilst I was looking at the Fastrac the customer asked me if I knew much about the EGR system on a Sisu engine which was fitted to one of his Gleaner combine harvesters.
The Sisu engine is also used in the JCB fastrac tractors and is a very standard platform engine so I figured I would take a look. Talking to the customer, I asked what the issue was with the machine and he explained that the local dealer had been out numerous times in the past 7 days trying to repair the issue with no luck. The issue being an error message present on the instrument panel during the operation of the machine stating Unknown DTC Error Occurred. On the back of this and the dealers diagnosis an engine ECU, engine harness and an EGR controller unit have been ordered. Not exactly cheap parts and without any real evidence as to why they would be replaced.
It was late in the day when I got a chance to take a look at the harvester and with time against me, I took a CAN logger and quickly collected some data to review once back at home. Without the dealer tool it’s tricky to get fault codes but with it being J1939 and having the J1939 DA document we have a slight chance!
With the data downloaded we could filter out the data and look for ID’s that will help us get some direction before getting back to the machine. We know from the instrument panel that we have an unknown DTC present, not helpful in the sense it can’t tell you anything else but it does mean that an active DTC was on the network when we took the log file. Kvaser has a very good document that explains J1939 and DTC’s in more detail which can be found here - SAE J1939 Fundamentals. Looking through this we can see the PGN for Active Trouble Code is 65226 which in HEX is FECA. Using the filter tools in Excel we can quickly search to see if it’s present.
Here we have numerous packets and interesting when we look at the header and the last two bytes of the source address, they’ve all come from the Engine ECU. Using the information we have on the PGN 65226 we can pick apart the data to get an SPN for the DTC. This isn’t something to go through now but all the information is out there if you wish to do it yourself and after talking it through with Lindsay Davidson, we end up with an SPN 520393 - Received network data in error, occurred 4 times. The first packet actually indicated that the occurrence was only 3 times but clearly this is an active fault as it moved to 4 during the CAN log capture.
As this engine is also used with JCB, we cross checked this SPN with the JCB technical information to find a similar fault code indicating an issue with the CAN 2 circuit. Technical information being key here and fortunately the customer could supply me with the wiring diagram for the machine, we could isolate this network to just a few components, EGR, wastegate actuator, mass air flow sensor, Nox1 and 2 and the Def supply module. Customer had informed me earlier in the day that the DEF system wasn’t used on this machine and the dealer had informed him that the DEF system had no influence over the engine and could not cause the fault.
To make things easier to see, the CAN2 network has been redrawn below.
The math channels A+B and A-B have also been added here but right away I could see that CAN H and CAN L were both being pulled to ground. By using the decode table I could also look for packets of data that are invalid to back up the fault code. By clicking the Valid column header I can quickly organise the packets into those which failed to decode and then by double clicking the table row, the software will take me to the packet.
As you can see in the above image, the grounding meant a packet was destroyed and so wouldn’t decode. As both CAN H and CAN L were affected my first thought was it to be most likely a component issue.
By removing components from the network I could see how they affected my CAN signals and making use of all 4 channels, I added in channel C and D to monitor both ends of the network to ensure I didn’t miss anything. Again starting with the easiest components the MAF, Turbo and EGR were removed but none had an effect on the network suggesting it was on the other side of the connector between the engine and the aftertreatment harness.
As this machine is sold throughout the world, different countries have different regulations on emissions. In Australia there are no restrictions on emissions for off-highway machinery yet in the UK and parts of Europe, it is a lot more strict. For this reason, the wiring and some components are fitted to the machines yet not used with the operation of the machine. The easiest way to get rid of all of the components from the aftertreatment side of the harness was to disconnect which fortunately had a connector.
I unplugged the connector and the CAN 2 network stopped being pulled to ground. Although this did not verify a lot as I had removed the power and ground source from a number of components for that part of the harness, I decided to de-pin the CAN wires from the connector and run the machine. This in fact had the machine working correctly and the error was now gone.
Checking as much of the harness as I could without opening up the harness, I could not see any damage. I re-pinned the CAN wires into the CW2 connector and I made a small harness to bypass the unused parts of the aftertreatment harness and had to fit a new terminator resistor in line to complete the network.
I’m sure I could drill down further to find out the faulty component but during harvest customers need their machines ASAP. Maybe once the harvest is over, I’ll get the opportunity to head back to diagnose the root cause of the issue especially, as some of you may have noticed, the diagnostic socket for this CAN 2 network has no way of getting to the engine ECU.
I could not have been happier with an outcome that verifies how important Pico equipment is to me and how important it is for a customer to have someone that can supply them with the knowledge, and the tools, to get them going again. I was at the machine for 3 hours and the parts bill was Zero.
January 31 2022
great case study