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Discussion Starter #1
I'm mainly starting this thread as a collection of ideas for this issue. I've read a lot on these forums, and wanted to put together all thats been helpful under one topic. I also have a few odd ideas for a fix, and will post results here.

My van will stall, then refuse to start for 15-20 min. During that time, no gauges work and I get "NO BUS" displayed on odometer after a few seconds.

I replaced Plugs, wires, and coil as suggested. This made it run better, but did not prevent stalls or fix anything, though I understand the logic behind it. Also, similar issues in non-Chrysler vehicles are often ignition & heat related.

I've finally fixed all known vacuum leaks. This seems to make the stall slightly less likely to happen, but does not prevent it, and once the van stalls, NO BUS ensues.

I unplugged every connector on the vehicle I could find and sprayed with contact cleaner. No change noticed.
 

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No Bus means that there is a failure, probably a connector or harness, at or to the ECM. Look to that connector for the issue.
 

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Discussion Starter #3
One forum topic suggested the following: Key on, unplug and replug the right connecter on the ECU. This is about 90% affective in allowing a restart. However, if it hasn't sat long enough, it will immediately stall again. Can't seem to drive far this way, but it has gotten me off of main roads and parked safer to wait.

Banging on dash: This has worked once or twice. Low success rate, but still, a good smack on the dash over the steering wheel has on occasion allowed a restart.
 

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Discussion Starter #4
Bob Lincoln said:
No Bus means that there is a failure, probably a connector or harness, at or to the ECM. Look to that connector for the issue.
Yea, I've got a few troubleshooting trees to finish still. I'll be posting that info as I go. Just trying to post all I've found in one spot. What's taken me weeks and 5 forums to gather, would be nice for the next person to find it all in one thread. Not saying I'm good enough for a tech right up, but the combined wisdom of others in one spot would make things easier to solve...
 

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NssJ said:
Banging on dash: This has worked once or twice. Low success rate, but still, a good smack on the dash over the steering wheel has on occasion allowed a restart.
Sometimes it's just good for stress relief...

I wonder if there's a harness connection at the firewall that has a problem.
 

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The bus voltages actually originate from the instrument cluster. Loss of communication may cause a stall.
I would remove the cluster and check the solder joints at the larger pins on the circuit board for fractures. It might appear as a circular crack around the soldered pin.
A good mechanical shock like a fist thump can bring it back.
 

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Discussion Starter #7
Going to check gauge cluster solder joints this weekend. Will update more as I press on.
 

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Discussion Starter #8
Another thing I'm starting to notice, a direct correlation between the NO BUS stalls and ECU temperature. Even if the engine temp is cooled down all the way on the gauge, it still may act up if underhood temp is high overall.
Popping the hood seems to lessen wait time. Fully opening the hood drastically lessens the wait time for restarting. When the ECU is hot/warm to the touch, it often won't start, but once it's cooled off, it usually has no issues.
Running the vehicle's heater (& rear heater) doesn't seem to help anything, and may actually make stalls occur more. I'm still testing this. I'm guessing the HVAC heater hoses running directly under the ECU don't help. Whatever heat may be wicked off the engine via HVAC is indirectly heating the ECU up more by proximity, so not really helping anything.
Driving with the hood cracked open seems to prolong the stall. I'm guessing more airflow into the engine bay and up towards the computer keeps it's temp down.

I have a few desktop computer fans on order. $7 for 3 vs $700 for an ECU without vin conflicts seems worth a shot. It may be symptom management and not a solution, but I'm curious to see if some electric fans can stop a lot of this... I'm sure placing the ECU 6in over a big V8 was not the best engineering location. I'm guessing relocating the ECU might have similar effects to cooling fans, but fans seemed easier and more reliable than splicing longer wires for the ECU to be moved elsewhere.
 

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Discussion Starter #9
PCM cooling fans installed. 2 40mm fans on top. The 100mm wouldnt fit between the mounts on the firewall, so a slightly smaller one is on order to go on the back of the pcm. 2 pos on-on switch. 1 position is on only when key is on, 2 position is always on. This way its always on when the vans running, but I can just turn fans on by themselves if I'm stuck waiting for it to cool.

This did not cure the NO BUS, nor did I think it really would. However, wait time to restart is drastically reduced. After a stall, it takes 5-10 min before I can restart it now vs. up to an hour before. So for about $15 total, this bandaid makes things more manageable until I find the actual cause...


backside, half of upper fans hang over, will have a larger fan pushing this cooler air directly on the back of pcm.



fans hang over front edge to blow directly onto pcm (and firewall clearance issues)



fans sit up against lip on top of pcm.



installed.

Not fixed, but I can make a trip with more than one stop without waiting an hour everywhere I turn the van off at... Improvement!
 

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Discussion Starter #10
Pulled and dissembled Gauge cluster. No noticeable cracks in any solder joints on either side. Redid solder on all the pins for the clusters 2 connectors. Didn't see anything there, but every youtube video I saw with people soldering gauge circuit boards, all the problems were always where the connector was. I'm guessing added stress from basically mounting at those points as well.

Test drove, still stalls. No Changes.
 

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Discussion Starter #12
ImperialCrown said:
I would look for a good used or reman PCM.
I'm sure it will come to that, but I'm trying to exhaust all other options first. Also don't wanna install a new pcm, then cook it with whatever is destroying this one...

Where else can I get a reman one? From what I'd read, it seemed like it needed to be from the dealer only, or it would have compatibility issues...
 

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They are out there at parts stores and online as well. Google the PCM part # and put an 'R' for a Chrysler reman in front of the part number. Looks like the number ends in 389AE? Search for Chrysler PCM 56040389AF?
 

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Discussion Starter #14
Ok, cool.

Do I have to get a dealer scan tool to load the vin, or can most 2 way scanners do it?
 

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It usually takes a more advanced scan tool to install VIN and mileage, but that shouldn't prevent it from starting and running. The dealer DRB III could do it if you so desire. The latest and greatest software version (flash) is also desireable. That could be done by the dealer at the same time.
If you are getting a PCM from a vendor, they usually offer to download the VIN and mileage before shipping it out to you.
Mileage for the odometer is stored elsewhere, so the PCM mileage doesn't really matter.
 

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There are PCM vendors on eBay who will program the VIN and mileage for you. I bought a reman one from one of them to put a stock PCM in place of the Mopar Performance PCM in the previous Dakota so I could go back to regular gas.
 

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Discussion Starter #17
Before I get a PCM, figured I’d finish up the rest of the troubleshooting to eliminate anything else, and prevent cooking a new part too.

Ok, I was following this pages troubleshooting tree. I’m not fully sure what all these values mean, just wanted to post my findings so maybe someone can explain, or see something obviously wrong within my numbers…I’m a little out of order, and a few extra suggestions were also checked at this time (some semi redundant info)

http://www.justanswer.com/dodge/7fsbv-ram-van-3500-i-ve-pcm-issues-dodge-ram-van.html

DLC
Pin 3 VT/BR: 2.48V
Pin 11 WT/BK: 2.45V

PCM disconected, batt neg disco C1 grounds check:
A-4 to battery ground: open
A-31 to ground: 0ohms
A-32 to ground: 0ohms

Backprobe Check PCM A4 to ground variations:
Key off, eng off: 0.1ohms
Key On, eng off: 4.3ohms
Key On, eng On: 7.1-7.8ohms (fluctuates)
PCM disconnected: open

Check for short to gnd (back probed)
A17 to gnd: 1592ohms
B31 to gnd: 1594ohms

PCM C1 Black 5V & sensor gnd (C1 disco)
A17: 5.16V, no short to gnd, no short to B+ 12V
A4 to A17: 567 ohms

PCM C1 Black 12V pwr & gnds(PCM disco)
A2: 12V key on, 0V key off
A22: 12.54V
A31/A32: 0ohms gnd key off, 1ohm gnd key on
Also used a test light on all 4, to opposite battery pole. All 4 lit bright = to across battery, so no noticeable voltage drops in these circuits

PCM C2 White 5V Sensor (PCM disco)
Pin 31: 5.15V, no short to gnd, no short to B+ 12V

PCM connected, Batt Connected, key off (backprobe) checking for shorts between 5V,12V, & gnd
A4 to Batt-: 0ohms
A4 to Batt+: open
A4 to A31: 0ohms
A4 to A32: 0ohms
A17 to Batt-: 1573ohms
B30 to Batt+: open(after one sec)

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The Transmission Solenoid connector does show signs of ATF staining on that harness up a few inches. I took off about a foot of electrical tape to inspect, wiped wires down. All wires look great, no damage, insulation solid and not falling apart.


Trans Short check via PCM (PCM disco, trans connected):
B31 to B8: open
B31 to B11: open
B31 to B12: 7.30Kohms
B31 to B30 7.36Kohms

Trans Short check via PCM (PCM disco, trans disco)
B31 to B8: open
B31 to B11: open
B31 to B12: open
B31 to B30 open
B30 to B8: open
B30 to B11: open
B29 to B8,11,12,30,31: open
B30-B12: 84.5ohms

B8 to gnd: open
B11 to gnd: open
B12 to gnd: 18.7ohms (also same ohms to A$ sensor gnd)
B29 to gnd: open
B30 to gnd: 80.2ohms (also same ohms to A$ sensor gnd)
B31 to gnd: open



Ran a loop with jumper cables to test wire resistances:
PCM C2 White to Trans Solenoid Assembly Connector Black (8-pin)
B29 to T4: 0.2ohms (Governor Pressure Solenoid x2)
B30 to T1: open (Trans Relay Cont to Trans Relay Control Output)
B30 to T3: 72.5ohms (Trans Relay Cont - Sensor gnd)
B31 to T2: 0.1ohms (5V power supply)
from the descriptions of the pins in the factory service manual, I thought B30 (Transmission control relay control) should be the same wire as T1 (transmission control relay output), but those 2 are open to each other. B30 instead was closest to T3(sensor ground) at 72.5ohms. This all confused me.

disconnected jumper loop:
No trans solenoid connector pins/wires shorted to each other

Trans solenoid connector assy:
Pin 2 VT/WT: 5.15V key on, not short to B+ 12V, 1831ohms to gnd?
Pin 3: 0ohms to gnd key off, 4.1ohms to gnd key on

Trans Solenoid Assy PCM disco:
Pins 1-8 are not shorted to gnd or B+ 12V

Trans Solenoid Assy PCM connected:
Pin 1: open
Pin 2:1831ohms to gnd, open to B+(after 1 sec)
Pin 3: 0ohms to gnd, not short to B+ 12V
Pin 4: 8.89Kohms to gnd, 1490ohms to B+ 12V
Pin 5: open
Pin 6: open to gnd, 6.22Kohms to B+
Pin 7: open to gnd, 6.22Kohms to B+
Pin 8: 889Kohms to gnd, 1498ohms to B+ 12V


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Sensors:
PCM Disco, ohms checks (from PCM):
A4 (sensor ground) to B31 (5 v supply - trans) = 6.67Kohms
A17 to B31 = 7.24Kohms
A17 to A4 = 567ohms
A17 to A8 (ckps) = open
A17 to A15 (IAT) = 17.15Kohms
A17 to A16 (ECT) = 17.64Kohms
A17 to A18 (cmps) = open
A17 to A23 (tps) = 1055ohms
A17 to A27 (MAP) = open
A17 to C25 (generator driver) = open
A17 to C 15(batt temp) = 18.94Kohms
A4 to B29 (GPS signal) = open
A4 to B31 (5 supply secondary) = 6.67Kohms
A4 to B1 (Trans Temp) = 1806ohms


TPS
Pin 1: 5.16V
Pin 3: 0ohms to gnd
Pin 1 to Pin 3: open after 1 sec

Cam Pos Sensor
Pin 2: 0.1 ohms to gnd
Pin 3: 5.16V
Pin 2 to pin 3: open (after one sec)

Crank Pos Sensor
Pin 2: 0.1ohms to gnd
Pin 3: 5.17V
Pin 2 to pin 3: open (after one sec)

found one pinch/chafed wire on trans harness, it went to one of the 02 sensors. cut pinch out and put butt splice in. Didn't seem to change anything.

O2 sensors PCM connected:
Pin 1: 7.22kohms to Batt+, not shorted to ground, not shorted to other wires
Pin 2: 1.6ohms to gnd, 0ohms to pin 3 (gnd), not shorted to B+ or other wires
Pin 3: 4.7ohms to gnd, 0ohms to pin 2 (gnd), not shorted to B+ or other wires
Pin 4: 7.22kohms to Batt+, not shorted to gnd or other wires

O2 sensors PCM disconnected:
Pin 1: open to B+, gnd, other wires
Pin 2: 0 ohms to gnd, open to B+ and other wires.
Pin 3: open to gnd (sensor gnd wire)
Pin 4: open to B+, gnd, other wires

Both O2 sensors wiring shot identical. Pins 1,2,3 were 0.1ohms to the other corresponding 1,2,3.
Pin 4 on both was open to each other, and appears not to be a shared line anyways.

PCM connected:
Pins 2 & 3 are 0ohms to each other and gnd
PCM disco:
Only pin 2 gets gnd, no more continuity between 2 to 3


One thing that did stand out as odd to me: Shooting some pins to ground, or shooting between pins at a sensor, it would flash random ohms for a second, then go open. I was guessing this might be shooting into the PCM, and the circuitry inside it does something for a split second. Tried with PCM unplugged, and still got 1sec of ohms, then open. Could just be cheap multimeter acting up…
 

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Discussion Starter #18
Cleaned all grounds with wire wheel, reassembled with dielectric grease. Grounds found: firewall over battery. Firewall under/inward brake booster, firewall passenger side (2), ignition coil, passenger fender, behind glove box, and drivers side head front and rear.

Drove van til warm, then kept it running in driveway until the usual stall. Stalled about the same as always. Gauges stayed put this time though. It restarted instantly. Ran rough, but still ran right away, and did not stall. Engine evened out after playing with throttle a bit. 15min, wouldn’t stall again. Shut off.

Self test, no codes “P Done”.
Did cluster self test, seemed fine. Noticed a few lights weren’t on during it though. Restarted engine, started right up, no issues. Turned on Hazards to check gauge bulbs, worked fine. High beams also displayed, though not during cluster test either. .

Then for some reason, I turned on the headlights. Immediate stall, all gauges drop. Finally get No Bus again. Not sure if had anything to do with headlights specifically, or alternator amping up…

Cleaned headlight switch connectors. Looked for grounds under dash, only found the glove box one. Cleaned it then. Looked for more grounds near front and rear lights, none found. Cleaned both front turn signal and headlight connectors.

Drove again and wouldn’t stall. I had about a 24hr period where I couldn’t force the stall/NO BUS regardless how many short trips, hot engine restarts, etc. After that day of luck though, its back to normal problem Stalls when hot and instant No Bus displayed. So cleaning grounds did something, and cleaning all lighting connectors did more, but neither had lasting effects.
 

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The Hazard and Highbeam indicators are hardwired in the cluster and not on the bus. They aren't included in the self-test.
You may have more going on here than the PCM if the stall happened and the gauges were still up. Active gauges would indicate that the bus was still up.
There are more instrument panel grounds than the glovebox one. There should be column to body and 1 or 2 grounds on the dash sides (maybe hidden underneath the kickpanels)? If the headlights killed the bus and stalled the engine, you likely have another poor connection somewhere. Maybe the PCM isn't the problem after all?
 

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Discussion Starter #20
Still haven't found anymore grounds under the dash. I have cleaned every connector except the fuel pump cause I have too much gas to drop the tank. I was hoping it might be a short with the lighting, but after 24hrs, its back to stalling like normal with immediate no bus. Starts and drives fine again after comp has cooled down...

I finished with that sites wire shooting checklist. If I run out of ideas, I may pay there to get the same guy to look over my findings.
I did the troubleshooting chart for No Bus out of the factory manuals, will post that here too.
Tested all sensors and sensor wiring and will post all that here shortly too. Found some good youtube videos from a Jeep with PCM issues, and have some more to check from that. No solutions yet, but at least narrowing down everything else so if I get a new PCM, I don't fry it anytime soon.

Will post the rest of my wire shooting later.
 
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