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No Bus

Discussion in 'Vans' started by NssJ, Apr 18, 2013.

  1. TWX

    TWX DO NOT FEED THE TROLLS!
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    I'm curious as to what the heck happened to this van along the way before it came into your possession. Having driven vans as old as an '84 Maxiwagon and as new as the '01 that I'm in now, the biggest problems I've seen have been a bad clockspring in the '84 that messed up the horn along with a cracked exhaust manifold and a failed starter, and another cracked exhaust manifold on the '97 I drove for awhile. One other van in the little fleet has a bad sensor in the transmission but it still seems to run OK, and my current '01 may have an oil pressure sending unit that's on the fritz.

    I'm starting to wonder if this van was ever submerged in water or something, based on all of these gremlins that you're finding. I hope not for your sake, but this is an awful lot of trouble for a vehicle design that's been fairly robust.
     
  2. NssJ

    NssJ Member

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    It was a "church van" in Louisiana, though looked more like a bastard child academy bus (interior picked/torn apart). I got it from a kid in Mississippi for a trade. He didn't register it, so no telling who had it from LA to MS.

    Someone was definitely 4-wheeling it despite 2wd, the mud caked undercarriage shows. It's been ran head on into a tree , stump, or telephone pole; smooth round center bumper dent. It had no jack when I got it, but one of the previous owners tried jacking up via body "pinch weld", nice caved in spot on both sides. It had 4 bald tires, no spare, one rim was a chevy 8-lug that did not fit right (400mi drive home like this). No real brakes either. Intake bolt broke off, and just set gently in its hole. Coolant temp sensor pulled apart, and JB welded back together. Coolant was like diluted orange dex-cool with rust, water pump nearly ate through itself. Orange RTV on everything, like they put it on the fan, then ran it to see...

    I'm sure there's more I've forgot, lol.

    Basically, its been abused by a lot of people, and all maintenance neglected for quite some time. I guess, the quality of engineering shows if it's survived all this and hasn't been junked yet. After knocking out all the mud, the underbody looks fine. no real rust on anything but the rear seat latch drain holes. I don't think it got submerged thankfully. Overall though, a $2000 trade for an 00 van with 91,000 miles, I'm ok with a few gremlins. Wiring's easy for me, that timing chain was a lot harder than I expected though, all downhill from here..
     
  3. NssJ

    NssJ Member

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    This is the last of the trouble shooting following
    http://www.justanswer.com/dodge/7fsbv-ram-van-3500-i-ve-pcm-issues-dodge-ram-van.html
    So I have all the data, just not sure what some of this means.


    Backprobe check for short to gnd:
    A17: 1592ohms to gnd
    B31: 1594ohms to gnd
    A4 sensor gnd: 0.1ohms PCM connected, OPEN PCM disco

    Engine Running Backprobed for running voltages:
    PCM C! Black
    A17 5V supp: 5.16V
    A22 fused B+ 12V: 14.03V
    A4 Sensor gnd: low voltage, counts down to 0V
    A31 gnd: 0V
    A32 gnd: 0.02V down to 0V

    PCM C2 White
    B25 gnd: 2.49V rolled down to 0V
    B315V supp: 5.16V


    Next, Factory Service Manual...
     
  4. NssJ

    NssJ Member

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    Factory Service Manual: No Bus diag chart
    Key off, eng off:
    Measure CCD Bus circuits for < 5.0ohms

    CCD Bus(+)
    Instrument cluster C! black passenger side -> PCM C3 Grey
    IC1 pin 10 – PCM pin C30 = 0.1ohms
    - PCM pin C28 = open (no cross bus short)
    CCD Bus (-)
    Cluster C1 black passenger -> PCM C3 Grey
    IC1 pin 9 – PCM pin C28 = 0.1ohms
    - PCM pin C30 = open

    That’s their only help. Shoot those, if good, replace cluster, the replace PCM if still fails. Least I got wiring diagrams and connector pinouts from them. Haynes was lacking horribly on a manual covering 1971-2003…

    I also checked these gauge cluster wires against PCM 12V B+, 5V reference, sensor ground, and ground to make sure nothing shorted elsewhere.

    Instrument Cluster C1 black passengers
    IC1 pin 4 gnd = 0.3ohm to gnd, OPEN to B+ 12V
    OPEN to PCM C! A17 (%v)
    IC1 Pin 6 B+ = OPEN to gnd, -1.3ohms ? to B+( cause it was still attached to battery)
    12.82 V (key on), PCM A17 = OPEN

    Instrument Cluster C2 grey drivers
    IC2 pin 7 gnd = 0.3ohms to gnd, OPEN to B+ 12V
    OPEN to PCM C1 Blk A17 (5V ref)
     
  5. NssJ

    NssJ Member

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    90mm cooling fan installed on rear of bracket. Can feel cool air blowing about 1ft to each side of the PCM...

    [​IMG]
    so about $20, and Ram Van is high class like a Land Rover, lol.
     
  6. NssJ

    NssJ Member

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    Ok, this, made sense out of half of what I've been doing. I guess, seeing it in action, clarified a lot of things for me...

    http://www.youtube.com/watch?v=a-d6-jrGidA

    Though I disagree with being so lazy you'd snip a wire vs. just crawling under the vehicle and unplugging a sensor...
    Otherwise useful info though.
     
  7. NssJ

    NssJ Member

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    I stalled the van in my driveway, then went to check 5V signal on sensors while the No Bus was present. 0.46V showed while No Bus was happening. I went around the van unplugging every sensor on those circuits to see if one was the short. TPS, MAP, Crank Position Sensor, Cam Pos Sensor, fuel pressure sensor all on PCM A17. PCM B31 has Vehicle speed sensor, transmission pressure sensor, fuel gauge sensor. Nothing I unplugged restored the 5V signal. I went around and started unplugging pretty much everything else aside from the PCM. No other components causing short.

    Unplug PCM, voltage goes to 0. plug back in, 5.16V is restored. Finally got the bright idea. Tap on the PCM. Tap on the front of it with my fingers, 5V shorts out again. Tap again, 5V restored. So:

    NO BUS troubleshooting STEP 1: tap on PCM to see if problem goes away!

    I repeated it several times. I also made sure I didn't bump PCM wiring when tapping, to rule that out. I peeled back about 1ft of electrical tape off all 3 PCM connectors to check; all wires looked fine.

    As a last ditch effort, followed another Jeep PCM video's advice

    https://www.youtube.com/watch?NR=1&feature=endscreen&v=xrd9k9QBST4

    Since I know the PCM is bad anyways, I was no longer worried about breaking something bending pins up. Cleaned connectors, dielectric greased female side, bent all male pins up 5-10* angle. Connectors feel much more snug on there. Will drive and see, but not expecting a miracle here.
     
  8. NssJ

    NssJ Member

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    Does anyone have any good objections why not to get a Cardone Reman PCM from autozone?

    I need to buy one somewhere I can go back to regardless what state I'm in on the drive back to CO. 3 choices are Dodge dealer, Autozone, and O'Reilly's.
    Dealer costs more.
    O'Reillys is "defective workmanship" warranty only, which may be hard to honor.
    Autozone is 1yr unlimited warranty, so if I did manage to miss a wiring short and cook a new PCM, I can just stop at one and trade it out. Also, Autozone said 1 day to ship one here. probably not always the case, but low wait time is good. The less time I'd be stranded anywhere, the better.

    Just wanna know if anyone has had any bad experience on a PCM from them that I should avoid.

    Thanks
     
  9. TWX

    TWX DO NOT FEED THE TROLLS!
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    In your shoes I'd go with the Autozone one too, but I'd drive it around quite a bit before the road trip to be sure that it's working right.

    Is there a core charge or do you have to turn in your existing PCM in order to get the new one? I ask because while this one is a PITA, it does let you limp along, so it's the computer equivalent of the donut tire...
     
  10. ImperialCrown

    ImperialCrown Moderator
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    Agree. Reman PCM's get some testing, but of course those with intermittent electrical/temperature issues may make it back into the parts pipeline over and over again. They can't test it for every possibility, especially if they don't see it fail on the bench and that is what a warranty is for.
    I hope that you get a good one right off the bat, but give it a shakedown drive first to make sure. I have had to turn in defective remans on a return trip to get a good one.
     
  11. NssJ

    NssJ Member

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    Another Jeep PCM video.

    https://www.youtube.com/watch?v=uY62r-rtvls

    If I had a Cherokee, this would have worked. Sadly, there's no voltage board on the front of Ram Van PCMs. Everything is in the back of the case, and covered in an inch of jello potting. Potting also does not want to come out even with a heat gun, so instead of chiseling into the board, I passed on this idea.

    I do have to give credit to all these Jeep owners who recklessly dive into unorthodox PCM repairs. Inspirational, though not always applicable.
    Also kind of cool, it appears Chrysler uses the same pin numbers and wire colors for their PCMs on multiple vehicles. So What I learn here, will likely be applicable later too.
     
  12. NssJ

    NssJ Member

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    Reman PCM from Autozone came in. The aluminum shell of the PCM was cracked, so went and returned it. It was the last one they could order apparently.
    Went to O'Reillys and ordered one immediately, so no chance of the cracked one coming back to me if they shared the same supplier... :thumbsup:


    Unfortunately, O'Reillys doesn't have the idiot proof warranty AZ did. So, following the instructions that came with the new PCM I have a few more checks to do. [SIZE=11pt]“Injector and Coil circuits must not be shorted before installing the new PCM”[/SIZE]. Have a few more pages of wires to shoot now, but will be worth it if it helps secure the warranty; proof that I checked everything possible first with written documentation...

    Will update more when I get through.
     
  13. NssJ

    NssJ Member

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    Checked ignition and fuel systems for shorts as new part recommended... Just kind of checked against everything else for shorts. For a $400 part, seems worth doing to ensure my warranty.
    I've been reading and watching videos, but I don't quite understand the ASD. it seems like the ASD is what supplies primary voltage to fuel/ignition as long as PCM tells it to. If that's the case, I don't get why everything shows a path to gnd either no ohms, or a set value of ohms...


    Part checks:
    Tested ignition coil (new part, but checked anyways)
    Primary circuit: 1.0ohms normal, 1.5ohms hot during No Bus stall
    secondary circuit: 11,940ohms normal, 15,000 hot during No Bus.

    Injectors: 12.3-12.5 ohms normal, 14.8-15.2 hot during fail.

    Wire Resistances(Coil, Injectors, and PCM all disconnected):
    Ignition & fuel injector drivers shot 0-0.3ohms to their respective pins at the PCM end.
    Ignition and injector ASD circuits shot 115.4ohms to PCM C3 (ASD cont), and 0.2ohms to PCM C12 (ASD cont)

    I wasn't sure where the ASD pins were supposed to shoot to exactly, so checked at both. Are they supposed to shoot clean to one line, but then have a set resistance to the other? These were with both ends disconnected...

    Fuel/Ign connector short checks:
    Nothing was shorted between its 2 pins.
    Driver pins were not shorted to ground.
    ASD pins to gnd: Ignition 8.4ohms, Injectors 6.1 ohms.
    recheck during fail:
    no direct shorts still, driver pins not shorted to gnd,
    ASD to pins to gnd: Ignition 8.5ohms, injectors up to 9.1ohms

    Ign/fuel short checks at PCM (parts and pcm disco)
    Shot primary injector and primary coil pins at pcm for shorts to: A4 sensor gnd, A17 5v supply, A22 B+ 12v, A31/32 gnd, C3 ASD, C12 ASD, and all to each other.
    Almost everything shot open, no shorts between anything.
    During NO BUS fail, all opens stayed open.

    note: did have to disconnect O2 sensors for this, as they share the ASD circuit, and showed a set ohm value to gnd.
     
  14. NssJ

    NssJ Member

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    PCM, ASD relay, fuel injectors, ignition coil, and O2 sensors still disconnected.
    Shot ASD relay, no shorts, pin85 to 86 is 77.5ohms (within spec)

    Shot ASD connector pins to PCM, wires had 0-low ohms to themselves, no direct shorts
    Shot all ASD connector pins (in PDC) to eachother, power, gnd.

    What pins are connected to what:
    PCM A2/ASD D1(pin 85) Fused ignition switch output:
    PCM C3/ASD D2(pin 86) ASD relay control
    PCM A22/ASD D3(pin 30) Fused B+ 12V
    D4: open slot.
    PCM C12/ASD D5(pin 87)

    Confusing part:
    D1 to D3 has 0V key off, 12V key on between them. Ohms could only be shot after disconnecting batt neg: 0.8ohms key on, 142ohms key off
    D1 to gnd:0V key off, 12V key on, Ohms could only be shot after disconnecting batt neg: 39.5ohms key off, 17.3ohms key on.

    Questions:
    Which is the gnd D1(85) or D2(86) for the relay control circuit?
    Do both relay input voltages basically come together when the ignition is on(D1&D3)? Hence the continuity between them?
    Why is D1(85)so low in ohms to gnd if it also shows 12V positive?

    I've managed to thoroughly confuse myself at this point over something that seems it should be simple and obvious. Help would be appreciated.
     
  15. ImperialCrown

    ImperialCrown Moderator
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    I don't have a wiring diagram to follow at this computer and can't seem to find one on Google either. Lots of early carburetted Dodge and later GM/Ford EFI images, but nothing I can use.
    If you wanted to e-mail me an engine electrical diagram that you are using, I could tell you if your readings make sense to me or not.
    Both ASD actuator coil (+) and contact (+) are battery power as far as I know. The PCM grounds the actuator coil prior to engine cranking. I believe that the ASD directly feeds the ign coil (+), injector (+) side, O2 heaters and fuel pump relay (+).
     
  16. NssJ

    NssJ Member

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    Yea, I wrote what each pin went to for some clarity.
    The PCM pin is what's directly connected to that ASD pin
    D# is the ASD connector socket it goes in on fuse panel(in bold).
    description of what the line is called.
    and the generic relay pin# (in parenthesis)

    Schematics, ASD & PCM pinouts:
    http://s1194.photobucket.com/user/N55J/library/ASD%20schematics
    they are big enough you can see them clearly as long as you click Download in the bottom right, rather than just save image.
     
  17. NssJ

    NssJ Member

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    I'm asking because something doesn't seem right. For the relay to function, either 85 or 86 has to be power, the other has to be ground.

    Pin 85 is 32.5ohms to gnd
    Pin 85 is open to B+.
    Key on, pin 85 has 12V+ when shot to gnd. 0V to B+

    Pin 86 is open to gnd
    Pin 86 is open to B+
    Key on/off, and removing negative battery terminal don't change these.
    Pin 86 shows 12V- when shot to B+, so it completes voltage like it is a ground, even though it has no continuity to ground. This shows with key off even.

    85 seems closer to gnd than 86, but 85 clearly gets key on +voltage..
     
  18. ImperialCrown

    ImperialCrown Moderator
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    85 is 'ignition on' +12 v power.
    86 is grounded through the PCM (-) when the PCM gives the OK to actuate the relay coil.
    30 is battery +12 v all the time power. You may read a little resistance to ground through the alternator diodes with an ohmmeter with the battery disconnected, but this would be open-to-ground for all practical purposes according to the battery.
    87 is switched +12 v out to the ign. coil, injectors and O2 heater loads.
    The ASD circuit numbers look like they should be OK.
     
  19. NssJ

    NssJ Member

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    Thanks
    Just wanted to double check. Seeing 35ohms to gnd on a power line(85) concerned me. Having flowing volts on 86, yet no continuity to ground made me confused; 86 was defying electricity...

    Will put the new PCM in this week when I have time...
     
  20. NssJ

    NssJ Member

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    The Good: new PCM installed. Didn't even start rough. Started right up with no gas (old PCM would die a few times if the -batt cable had been off).
    Ran and drove good, idle seems lower and better. No Check engine light. Couldn't get it to stall, though only had an hour to mess with it today.

    The Bad: BRAKE and (ABS) lights on. Sounds like vin mismatch from reading other threads.

    Can the vin be loaded by any mechanic shop scan tool, or is this a dealer only reflash?
    Thanks
     

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