How to display error / fault codes 2001 Dodge Ram?

I was beginning to reach that conclusion as a result of searching for references to the ECM on the web.

Several times.

Update:

I gave up trying to remove the dashboard cover. I did remove the lower driver-side dash trim, the instrument-cluster trim ring, and removed the instrument cluster. Removed the cluster PC board, no dammaged components (looked brand new), noticed that a couple of LED's weren't installed. Optional indicators I guess - one is labelled (on the PC board) as "water / door" and the other one as "security". No corresponding markings on the cluster bezel. For the hell of it, I soldered a couple of LED's in those positions (along with the necessary resistors). On the cluster display, they would show up above the "check engine" light.

There is a massive connector under the dash that's clipped to a metal bracket coming off the firewall. It's a combination of a large and medium-sized connector. The large one has about 60 contact positions (about 50 are used). Again, they're dry and no sign of corrosion. I re-seated both of them. I believe it's the cable that comes from the engine compartment through a hole in the firewall.

I did all this with the battery being disconnected (for about an hour or two). After cleaning the various plastic surfaces and mounting the cluster, I reconnected the battery, and again there's no change. When switched to the run (ignition) position, the gauges seem to move to their respective zero positions (battery to 8v, etc) and the odometer will eventually display "no buS" and the overhead will display CCD. I can, however, still start the engine (the tach reads zero).

I found the following:

and thought that perhaps it might be relavent. I do have remote lock/alarm/power seats and windows.

Specifically these symptoms:

- Engine Will Not Start (if equipped with Vehicle Theft Alarm) - No Communication With The DRBIII (No Response from CTM) - Essentially, all CTM controlled devices will not function if the CTM locks-up.

There are 2 connectors to this CTM box which is mounted under the dash. But even when it's unplugged, nothing changes.

Does this make much sense to you Tom? IF he is getting a no buss message, doesn't that indicate that the cluster is not talking to the computer or vise-versa. I doubt that he will get anything this way. If he wants the diag codes, I think that he will need to buy / borrow a code reader and connect to the ODBII port directly.

That sounds like a possible bad ground or bad connection between the cluster and the PCM sending bogus signals to the gauges.

On my '99 Durango slt 5.9l 4x4 I would get the "no bus" message in the trip odometer display when driving in stop and go traffic on hot days. The culprit was the PCM. It had developed a heat sensitive failure after about 30k miles. It would also shut down the vehicle and would not provide power to the coil until it had cooled off. Until I replaced the pcm I would carry a five gallon can of water to pour over it if and when it began to fail. I also did the front airflow mods on the passenger side front to help airflow in the pcm mounting area, as well as changing out the thermostat for a 185 degree unit per mopar performance. Allpar listed several cooling mods/changes like an improved fan shroud and swapping the fan with one with more blades from a viper but mine already had those from the factory.

Not any further failures since the pcm was replaced. A friend who used to man the Daimler help desk told me the cause of the pcm failure was hairline cracks caused from the PC board in the pcm heating up and cooling down hundreds of times eventually severing a circuit trace that would be fine until it heated up and expanded causing the trace to open slightly. The "no bus" error was generated because the pcm had shut down, ceasing communication with any of the other controllers in the vehicle, in this case the dash computer. I would also get error codes in the high 9xx range from the odometer readout. Hope this helps, good luck, Joe.

Yeah - that was already discussed, later that same day, in fact.

I get instrument cluster codes (by pressing the odo shaft when turning the ignition to on), but not PCM codes (by the 3-times off-on with the ignition key).

The cluster codes (if that's what they're called) were these:

900 920 921 940 950

Initially when this problem first appeared, the engine would turn over but wouldn't start. Then after an evening just sitting there, the problem completely went away for about a minute, during which time the engine did start, the guages worked, and I was able to get the odo to flash the (PCM?) codes using the 3-times off-on key sequence. Then the guages died and the problem came back (no buS, CCD) except that the engine now starts (but the guages still don't work).

I've been out of town for the past 2 days, during which time the truck has been in the garage (and out of the rain), and the problem is still there, but as mentioned above at least the engine now starts every time I try it (meaning that the PCM is working?).

During the brief time the problem went away, the PCM (?) codes I was getting were:

P0123 (Throttle Position (TP) Sensor Circuit High Voltage) P1687 (P1687 Driver 5 Line 7)

Alternate descriptions of 1687:

No Cluster BUS Message No J1850 messages received from the Mechanical Instrument Cluster (MIC) module

No MIC BUS Message No CCD/J1850 messages received from the Mechanical Instrument Cluster (MIC) module

No messages received from the Mechanical Instrument Cluster module

The P0123 code I can understand - since I did disconnect the TP connector to check for 5V at the connector - but I plugged it back in so I guess the code needs to be cleared?

What exactly is the P1687 code?

Since the cluster is housed in a plastic case that's screwed into a plastic dashboard, the grounding must be part of the 2 cluster connectors. Since I removed the cluster and re-installed it, (and the connections looked great) I doubt there's any connector issue at the cluster itself.

The Haynes book shows the circuits for the guages, but it doesn't show ANY circuits for the electronics in the cluster. The guage circuits don't seem to connect to any of the cluster electronics. If that were true, then the computer wouldn't have any sort of connection to the fuel gauge, in which case you wouldn't be able to read the fuel level through the ODB port (is this the case?).

As I mentioned before, the battery is fine, and when the engine is running, the voltage at the battery is 13.75.

Could the problem be located in the wiring bundle that enters the lower portion of the fuse assembly in the engine compartment, or perhaps some connection inside the fuse assembly?

The battery guage should at least read the battery voltage correctly. Are the guages run off a separate power supply somewhere?

First let me thank maxpower (aka Glenn Measley), miles, FMB, Nosey, TBone, Tom Lawrence, and Joe Brophy for the wealth of information and the detailed answers to my technical questions about the Chrysler Data Bus (tm)(C). My special thanks to Glen for giving me the encouragment to continue diagnosing this problem in my own driveway.

To recap:

2001 Dodge ram, short cab, 5.2L, 2WD, all options.

Truck ran fine one day, was parked overnight, there was rain that day and night, then the next morning engine would turn over but not start. After 2 days and some poking around (disconnecting/reconnecting various connectors) engine would start and briefly the guages worked for about a minute, then went dead, but engine could then be started at will after that.

When ignition is switched to on, odometer displays "no buS" and the overhead console displays "CCD".

Not having a proper wiring diagram, I focused on the wiring to the instrument cluster (MIC). There are 2 connectors (10 pins each) and after identifying all the ground and power pins, there were about 6 pins that were candidates for being "the bus". One of those pins was showing 40 ohms to ground, which I thought was strange.

I metered each of those 6 to the 3 connectors at the PCM and found that only 2 of them did indeed go to the PCM. As I suspected from examining much of the dashboard wiring, those wires are always a twisted pair - indicative of some sort of differential signaling, and I suspected they were indeed "the bus". One of those wires was the one showing 40 ohms to ground, and now I see it's showing 40 ohms to a third pin at the PCM (on a different connector).

Ok, so what I do next is this: with the 3 connectors at the PCM already off, I disconnect as much of that cable as possible. That basically means to disconnect it's opposite end from the main fuse module beside the battery (it's a big square connector with a hold-down bolt in the middle). Ok, I'm still reading 40 ohms - so what's going on? Under the truck, I disconnect a cable going to the transmission (it's got maybe 10 wires) and discover that one of those wires is the one making a 40-ohm connection to one of the bus wires (this is with all connectors still disconnected).

Ok, time to cut the main cable away from the firewall and remove all the black tape and physically inspect the twisted-pair bus wires. I do this all the way to the connector at the fuse module, and still get

40 ohms. The last thing is to take apart the square fuse-module connector. I do this, and as I manipulate the outer cover, the 40-ohm connection goes away. I manipulate the wires and manage to make the 40-ohm connection come and go.

I look closely at where the bus wires go inside this connector, and where the mystery wire to the transmission goes, and it turns out they're right beside each other. But what's really wierd is that there's no indication that they're touching. No corrosion, no chafing, no bared insulation. Very strange.

So I re-position the wires and close up and re-tape the connector, then re-tape the entire main cable back to the PCM connectors, and re-install all connectors and assemblies in the dash that I took apart.

Needless to say, the MIC worked fine, and no PCM or MIC codes were displayed when I tried the various diagnostic code reporting methods.

I'm thinking that this problem had nothing to do with the rain that happened the night before this problem started, but I still don't know why the engine wouldn't start during the early phase of this situation.

I'm glad I did this, and not simply take it to the dealership and maybe those monkeys wiggle something and the problem goes away only to come back later. At least now I know where to look if it happens again.

Gee thanks but I didnt encourage you to work on it!!, but im glad you got it fixed. I still think it is rain related.

Also I wont to say that I am one of those so called " Monkeys at the dealer" Let me know when you have another problem!!

Impressive tracking of the wiring through the harness(s), what you didn't say (if you are a mere mortal such as myself) is the difficulty in following the factory diagrams in the manual.

I know if I had not been in electronics field service and thus some exposure to how multi page diagrams are organized in general, and that a manufacturer usually has their own "adaptation" of a wiring standard could have easily reached the frustration level where I just took it to the dealer.

Congratulations on a long (and more difficult than you made it sound, I would guess) trek to find the offending component. I say that while also looking over my shoulder in panic thinking that if you have not uncovered a "visible" villain, there is a good chance it will return. I hope not, maybe it was a miniscule wire fragment that fell out when you unplugged a cable from a socket or something similar that made the bug disappear. Even if you have it return, judging by the level of detail in your post you will no doubt get it sooner than later, again congrats. regards, Joe

A few months ago, when I was picking up some front sway bar bushings for my 300m, I also wanted to get a service manual for it (Chiltons, etc). I have yet to come across any such manual for the late model LH cars. But I did find a Haynes manual for '94 to '01 Dodge Ram - so for the hell of it I bought it.

I had no problem following the wiring diagram in the book, except that it was way off the mark for my RAM. It must have been written for when the RAM didn't have an electronic instrument cluster. I went through all the diagrams and put together a picture of what the two dashboard connectors must look like, and according to the haynes book they'd each have to be 14 pins (instead of 10) so right off the bat I knew something was wrong.

replying to MoPar Man, thomas herron wrote: You can jump the ads relay

You REALLOY need to use an OBD2 scanner of some soirt.

2001 Dodge Ram 5.2, A neighbor replaced positive cable from battery to fuse /relay box without disconnecting from the battery and he shorted it out. Bl ew the fuel relay, so i replaced it. Would start up run for several minutes then die. After a few minutes run , then die. Reset the cluster ran fine a ll day. Next day will not start. No Bus Code 920,921,999. Tried resetting c luster same reading. Code 920,921,999. Disconnected batter terminals cleane d plugs to the PCM pulled cover off PCM it was dirty. Cleaned put it back t ogether reset cluster still same problem. Next I will pull the starter remo ve crank sensor clean and put back in. If anyone, has or had the same probl em please let me know. If after cleaning crank sensor and I still have the same issue, then I will replace the PCM. Trying to keep from buying parts a fter parts when the issue is elsewhere. THANKS TO ALL INQURIRES. What a pai n in the axx. Never let your neighbor work on your vehicle. Lesson Learned! !!

Maybe you can advise. 2001 Dodge Ram 1500 5.2. Neighbor replaced positIve c able from batterY to fuse/relay box without disconnecting from battery. He shorted it out! At first when running the alternator whinned,but no chargin g or running problems. The next day the truck just died, but cracked right back up. Later that day same thing, so I checked the relay to the fuel pum p because I could not hear it come on when you turned on the ignition. Repl aced fuel pump relay ran fine. Went to start the next day I get a No Bus re ading. Reset cluster good to go or so I thought. Back to the same problem o nly now, I get the codes 920,921,999. Pulled cluster checked connections a ll good. Went to PCM checked all connections,good. Yes, I disconnected the battery in case you were wondering. Any advice before I start replacing par ts after parts? It seems that this is a common issue with the Dodge. Never had any serious problems out of this truck for 13 years. Ofcourse, until I allowed my neighbor to replace such a simple cable. Should had done it myse lf. Lesson learned. Any help would be greatly appreciated. Troy Jones mrtro snipped-for-privacy@gmail.com