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Posted (edited)

Okay, fellas I need some help understanding what I'm seeing here.

 

Over the past several drives, when I first start the truck up the BRAKE and ABS lights might stay on for a short bit (less than a minute) and then go out.  Once or twice, I also caught the speedo popping up as I started to drive.  Like it was at 0, then suddenly popped up to whatever speed I was going, 20-ish MPH...  I wasn't really watching it, so I'd sorta see it happen just outside of my view.

 

Then today, idling for about a minute in a parking lot, about to leave, the NO BUS message appears in my odometer, the MIL, ABS, FUEL and the AIRBAG lights are illuminated, and I lose my gauges.  The truck still idles fine, and I was able to drive away, but was sluggish on acceleration and had to vary the throttle for upshifts. 

 

I get home and start troubleshooting.  I found multiple threads about NO BUS and P1698 (my only code) so start going down the PCM path.  I test for continuity/ground at C1 pins 30 and 31.  Tested for 12V at 2 and 22(?).  I can't recall the ohm on 30, so I'll have to go back out and check.  While in there, I took all three connectors off and shot both the male and female sides with electronic parts cleaner.  The connectors didn't look bad, but worth a cleaning anyways.  The grounds were tight.  In the fuse box, the bolts were all tight.  No fuses appeared blown.  Battery cables were all tight.  The large connector in the center of the firewall over the engine appeared to be tight. 

 

Reading online, it appears if a 5V sensor on the bus isn't behaving itself, that could cause the NO BUS problem.  Since I had the strange popping up speedo, along with the random ABS and BRAKE lights, I thought I'd try to eliminate that by unplugging the rear ABS sensor.  So the sensor is still in the differential housing, but the connector is just sitting there.  I take it out for a test drive, and I have a working speedo?  I thought the truck got it's speedo input from the rear ABS module?  Am I incorrect?  Still have the NO BUS problem.  Reconnected the sensor.

 

While under the hood, it sounds like a relay in the ABS module is rapidly clicking, randomly.  I recently had it rebuild by Module Masters, so not ruling out a problem with the ABS module.  Just saying it's low on the list of culprits right now.  But strange enough, when I take it out for a drive, the truck runs perfectly.  All the needles work correctly.  And the only light on the dash is the ABS light.

 

I'm at a stopping point for now.  So curious as to what you guys think I should check next.  And, let me know about where the speedo gets it's signal from??

Edited by cs15dah
further troubleshooting
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FSM has this to say:

 

BUS FAILURE VISUAL SYMPTOM DIAGNOSIS
The following visible symptoms or customer complaints,
alone or in combination, may indicate a CCD
data bus failure:
² Airbag Indicator Lamp and Malfuntion Indicator
Lamp (MIL) Illuminated
² Instrument Cluster Gauges (All) Inoperative

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Took my truck to Dodge today.  They troubleshot it and said they figured out it was the ABS module.  It's shorting out and putting a lot of garbage on the BUS line, so the truck's computer can't decipher any of the signals.  They disconnected the ABS module and their scanner was able to connect and talk to every module on the BUS.  Quoted me just over $1300 for a new ABS module.  I thanked them, paid the $140 diagnostic fee, and left.  I guess it's time to contact Module Masters and see about that 5-year warranty...  :(

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So I’m having a similar issue with a no bud code in the odometer screen. Truck is a 01 4x4 with an airdog lift pump and quadzilla adrenaline with iquad, everything else is stock.

the truck still runs and drives but gets stuck in 3rd. I can manually drop it to 1st or 2nd but can not get overdrive. The only thing on the cluster than works is the rpm gauge. The abs light and brake light come on and off every once in awhile, but the CEL , low fuel light and seatbelt light stay on continuously. 
I have tried to scan the pick up to pull codes but I get an error message on my scanner.

ive checked all the grounds, I’ve also cleaned and greased the connectors at the pcm, along the firewall, the cluster, and main connector at the fuse block. All fuses are good. I’ve also replaced the alternator cause my batteries were around 11v when I checked them. According to my quadzilla, my ecm voltage is 11.8-12v. It was at 11.1 before I changed the alternator. 
Any help is appreciated! I need to get this issue sorted quick. I need my truck next month for my move across the us. 

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