J1939 datalink and ABS

Discussion in 'International Forum' started by x509, Jul 31, 2021.

  1. x509

    x509 Bobtail Member

    5
    0
    Jul 31, 2021
    0
    I've got 2002 9200i with an ABS light on. I just bought it. Light came on when I replaced the bulb. Blink code 71 says datalink communication lost. I've read a lot about wiring problems on the datalink but don't understand how it is actually put together. Is it one pair (or set) of wires that runs all over the truck that systems like the ABS module and satellite systems hook into? Is there one connection point for this bus to plug into the ECM (Detroit 60) and other systems splice into this pair of wires? If the connection for J1939 is bad at the ECM would that cause other problems (there are several posts about instrument cluster problems that mention the J1939 bus)? If only the ABS system appears to have a problem would that suggest the wires from the ABS module to somewhere on the J1939 are bad but probably not where the J1939 connects to the ECM? (of course, it could be a bad ABS ECM too).
     
  2. Truckers Report Jobs

    Trucking Jobs in 30 seconds

    Every month 400 people find a job with the help of TruckersReport.

  3. QUALITYTRUCK

    QUALITYTRUCK Road Train Member

    1,599
    1,470
    Jun 14, 2009
    romulus,mi
    0
    Look at the round plastic bulkhead connector underhood that goes thru firewall on driver side. Twist it apart and look for corrosion in the pins. If not, you have chosen arguably the most difficult repair to diagnose. Look up all previous posts made by me and others regarding J1939 data link in search box. Good luck.
     
    D.Tibbitt and Heavyd Thank this.
  4. x509

    x509 Bobtail Member

    5
    0
    Jul 31, 2021
    0
    I checked that and saw no sign of corrosion at all. Looking at schematics I saw that pins 11-13 of that plug go to J1939 and the ECM. I checked the negative (-) pin (13 I think it was) for continuity to ground and had none so figured I have an open somewhere but figured I’d try to see what I would be looking for once I start crawling around to look at the ECM wiring. Is the negative side of the J1939 bus grounded? If I unplug that big connector from the engine side of the firewall is it safe to check for voltage across the pins (11 and 13)?
     
  5. ChuckMartel

    ChuckMartel Light Load Member

    117
    72
    Jan 22, 2021
    0
    Honestly your best bet now it to try and split the j1939 up into sections, disconnect from modules and load test with a headlight while wiggling. Like quality said, definitely the hardest code to diagnose.
     
    biopure22 Thanks this.
  6. biopure22

    biopure22 Bobtail Member

    35
    14
    Aug 22, 2021
    0
    Did you check your terminating resistors on the j1939 network and make sure it reads 60 ohms?
     
  7. x509

    x509 Bobtail Member

    5
    0
    Jul 31, 2021
    0
    I looked around for terminating resistors. But being not sure what I was looking for I didn’t find any. I did where the wires coming from the firewall connector had abraded at the frame enough to expose the wire. It looks like aluminum wire was used and about 8” of it oxidized inside the insulation. But I still get no continuity between the yellow and green at the firewall connector. I checked the connector that comes off the Detroit ECM and get 120 ohms between yellow and green. I get 0 ohms between the green on the ECM connector and the green at the firewall so I’ve lost the connection on the yellow wire probably where it spliced into the bus itself. I haven’t cut that open to get to it.

    120 ohms means the other 120 ohm terminating resistor isn’t connected. I did read on another post that the ECM might contain the other other resistor, so pulling the plug at the ECM and getting 120 would be a good reading of the J1939 bus. Any idea if this is correct?
     
  8. biopure22

    biopure22 Bobtail Member

    35
    14
    Aug 22, 2021
    0
    i cant find a wire diagram for your truck to find out where that other resistor is,but i do know if reading 120ohms that means a resistor is bad.I would just follow those green and yellow datalink wires and it will lead you to that terminating resistor.with both resistors working properly you should get a reading of 60 ohms.
     
  9. Inderjit

    Inderjit Light Load Member

    273
    323
    Sep 17, 2017
    0
    I just looked on Navistar's site and the electrical manual is available
    but it was scanned from a paper document to a PDF and its not
    searchable. I don't remember the specifications but a J1939 backbone harness can run the full length of the truck if needed.
    However the taps that devices need to connect to the backbone harness
    should not be more than 36" long if I remember correctly. The tap that
    connect to the ABS module if its behind the right kick panel is a lot longer
    than the recommended spec that is probably why the ABS module
    is the first device to complain when there is a data link problem. If the
    resistance on the data wires is 120 ohms one resistor is missing or
    not making connection. I would suspect that the data link resistors are
    located the front near the left side of the engine in the main harness
    and the rear either a short distance behind the cab in the left frame rail
    or on the harness going to the transmission possibly on the right side of
    the transmission. Both will be tie strapped to the harness. The should be
    2 pin black plastic Metri-pack connectors.

    I could try to email you the manual its 19 Megs so a big download.
    Do you have a good high speed internet connection? If so PM me
    your email and I will email it to you.
     
    Last edited: Aug 23, 2021
    RocketScott and biopure22 Thank this.
  10. biopure22

    biopure22 Bobtail Member

    35
    14
    Aug 22, 2021
    0
  11. x509

    x509 Bobtail Member

    5
    0
    Jul 31, 2021
    0
    That would be great. I have a very slow internet connection but could find a public wi-fi to download it. But, it appears that I haven't posted enough to be allowed to send a message to you. Can you put a link in this thread? Or enough of a link that I could use to find the 2002 guide? Closest I found was for 2005 but there appear to have been enough bus changes to make it not very good for figuring out a 2002.

    Thanks.
     
  • Truckers Report Jobs

    Trucking Jobs in 30 seconds

    Every month 400 people find a job with the help of TruckersReport.

  • Draft saved Draft deleted