I have a Dodge Ram 3500 Cab and Chassis (2WD), 5 speed manual. I have the both the ABS light and the brake light are on. The ABS light goes off when the truck starts, but then comes back on. I have replaces all the ABS sensors and that did not fix it. While the truck is running the Air Bag light comes on periodically, then the tach drops to 0 and when the light goes off the tack works again. Last night I was flipping the lights on and off and all of a sudden I got a no bus error, but the truck was still running. I turned it off and this morning started up with no error shown. I'm not sure where exactly to start and ideas?

 

Sounds like a wiring issue. I would start the truck and have somebody sit inside while you shake every harness you can reach and see if you can duplicate the problem

 

Either that, or plug in with a scanner that can read the SRS, and ABS systems, and see what they are whining about. Give you an idea of where to start looking at least.

 

I know on the 98 and Down Snap On scanner couldn't read ABS codes told you to do the trick to mske the light flash

 

I've been having intermittent electrical problems with my '98 ram 2500 diesel. Just posted a write up about my air bag troubles. In addition to my air bag issue, which I eventually repaired. I have a lot of electrical things shutting down randomly. While driving, and sometimes upon start up, radio, signal lights, power window, power locks, and windshield wipers shut down. The ABS light comes on also. Digital odometer stays on, but will not advance. Upon shutting off and restarting the engine, everything works again. Eventually it donned on me that all these things are run off the ignition switch "run" contacts. I ordered a new ignition switch, and will see if this cures my problem. Several years ago, my air bag and ABS lights were staying on. I removed the clock spring. The shop manual says that it is not repairable. But I removed the tiny screws that hold the cover on. They are miniature and seem to be torx. I was able to grip them with pliers or vice grips. Found a broken connection that connects the clock spring ribbon cable to a small junction board where the harness wires connect. Soldered it, and it worked for a few years. Not sure if a bad connection in your clock spring would be that cause of your trouble. It seems that ABS trouble should not be related to air bag system. Here in Canada, I paid about $200 for a new clock spring recently as first step of troubleshooting an air bag problem. If you're the States, it should be a lot less.

Not to insult your intelligence, but it is easy to overlook what should be obvious. Have you tried pulling and re-seating your ABS and air bag system fuses ? These should be labelled on your fuse box cover. Might need needle nose pliers. Some fuse boxes have a special fuse puller tool inside. My air bag fuses are a bother to pull. They have a special plastic housing around them. Have to pull out the plastic housing, and it extends out perhaps a half inch only, does not remove from the fuse box. Have to use a knife blade to release a tab that holds the plastic cover on. Gotta be careful, as the plastic is easy to break. While you have them out, make sure the filament looks good, or test with ohm meter or test light. My air bag fuses are in a small fuse compartment on the end of the dash panel just inside the driver's door. My ABS fuse is in the fuse panel on the driver's side inner fender.

I do not know what year your truck is. Some vehicles have a fluid level sensor in the brake reservoir. If it is there, you will see two wires that penetrate the reservoir. I'd guess that you have already checked fluid level, but if fluid level is good, the sensor could be bad, if your truck has one. I do not know why an ABS problem would effect the air bag light, but perhaps the code system is making only an ABS code but is causing the air bag light to illuminate by faulty design. My '98 only has rear ABS, quite a simple system. Four wheel ABS can be quite complex. Perhaps try pulling off and re-seating cable connectors at ABS electronic box.

While having air bag troubles, I discovered that upon start up, the air bag and ABS lights turn on for about 10 seconds, then go off. When a trouble code is present, it then turns on and stays on. If no code it stays off. This is all for a self check of systems. The initial few seconds are only a self test, and the lights being illuminated mean nothing about any faults for first ten seconds. When the self test is completed, if any lights turn on again, they indicate a real fault code.

Have you scanned for fault codes yet ? You will need a scanner that is air bag and ABS capable. These cost more than the basic cheap scanners. An SRS (air bag) and ABS capable scanner could be in the $150 to $200 ball park, or more. But I was quoted about $160 by a shop to scan and troubleshoot my air bag trouble. Without a scanner, you are digging in the dark. Even with a scanner, it will not tell you exactly what your problem is, it will only tell your what system or component(s) to start looking at. It is possible that replacing your ABS sensors fixed the problem, but the codes have not been cleared. You can clear codes with a scan tool and start from scratch to look for any new codes after you clear the old ones. With no scanner, the old time method of disconnecting the battery for a few minutes might work. To clear computer codes, both the positive and the negative terminals need to be disconnected, according to Scotty Kilmer. Scotty has a great car advice U-tube channel.

You may need to examine the ABS sensor wiring. It is possible that a short or open circuit exists in the wiring. This could be a big effort to trouble shoot. Would need to find the end of each wire where they tie into the ABS electronics and do some continuity testing of every wire. May be able to temporarily place a shorting clip lead across an end of a wire pair to do continuity tests with ohm meter. Or may need long test cables for your ohm meter to reach from under hood to each wheel. Before such effort, would be good to just visually examine the wires for damage. Check connectors at wheels for damage. A simple solution could be found by pulling the ABS electronic module connectors and re-seating.

Hope that you find your trouble quickly before spending many hours on a lot of testing and/or a lot of money.