Hi! I'm a new to posting here and have been browsing for weeks looking for information related to my problem but can not quite pinpoint the issue. Please help and sorry in advance for the long read!

I bought a 2000 Dodge Ram Van 2500 Cargo 5.2 a few months ago. I only drove it home and around the block a few times trying to figure out the problem. Check Engine light does not come on during the gauge check. after 10 seconds, the odometer reads NO BUS and the Check Engine light comes on. After 2 minutes the ABS light comes on. After it idles for 10-15 minutes OR i drive for 5 minutes the O/D off light comes on and it will not shift into overdrive. After another minute the Trans Temp light comes on. The trans pan is not hot to the touch. It has never had trouble starting or functioning in any other way.

I first ordered a PCM from ebay and installed it. No change

I then replaced the governor pressure sensor. No change

I then tested the wiring between the trans case and the pcm for the temp sensor. I have the same readings on both ends -- about 1.6k ohms cold, about 2k ohms warmed up (backprobing for voltage was low twos, i think about 2.0v cold and 2.6v when the lights come on). All of this stuff is well within normal range as far as i'm aware so i figured it

I was beginning to research how the CCD bus functions so I unplugged anti-lock computer, airbag computer, and all my sensors, crank, cam, tps, governor pressure, coolant temp to eliminate components. No Change. I was sure it was a bad cluster

I then ordered a new cluster from ebay and installed. only change was no the check engine light never comes on but i think the bulb might be burned out. I haven't taken it apart, just put the original back in.

There seems to be a miscommunication in the pcm about the trans temp because the light comes on and it kicks it out of o/d but but both pcms do the same thing! and the cluster is acting normally, the check engine light is controlled by the pcm, but if the cluster doesn't get an ON command in the first ten seconds it turns is on by itself. That tells me I have a miscommunication problem on the bus btwn the pcm and cluster but i have the same bus voltage at the dlc and pcm. I measure ~ 2.49 - 2.52v on either CCD pin on the DLC. I don't know if the trans temp thing is related because every other light and gauge is working fine, but it seems likely that they are somehow related. I just don't know where to look because everything i've tested seems to be operating the way it should. Thanks for reading.

 

zoinks. You covered a good deal there.

Here are a few thoughts ...

Have you inspected all the fuseable links that are back behind the battery and under the brake master cylinder?

Is the ground strap between the trans and the body/frame and/or engine clean secure and intact?

How are the harness wires? I only ask because when my van gets hot under the hood in the mist of summer over 96F, the engine turns off and the OD shows NO BUS. After it cools, everything works just fine. Either the PCM or the harness wires are frail due to mileage and high heat over the years.

Have you tried spraying CRC Electronic Cleaner into the three harness connectors? These are known to have oxidation/corrosion at times.

The PCM controls the shift points of the trans. If the trans is shifts just fine, then the BCM (gauge cluster) computer has an issue.

Also, the dreaded clock-spring in the steering wheel goes bad too causing PCM errors to crop up too. There was a recall on this some time back.

Other than that, I'm clueless.

 

Thanks for your response! I have not done anything you have mentioned, I'll be back at it tomorrow (or tonight if I can't sleep). The wires/insulation/connectors look great, and I checked the common connections for water, its been drying out in the garage for the last 30 days too! Trans shifts great until the lights come on, then it still shifts great except for the whole no overdrive thing. One more thought I had was if my PCM was replaced by someone before I owned it with the incorrect pcm would it cause these problems? The replacement pcm that I ordered from ebay says it's from a 1999 5.2l ram truck (it functions the same) , mine is a 2000 5.2l ram van. I ordered based on the part number on the one installed which is 111AD. I don't know how particular these things are since I swapped in the one from my '97 for a few minutes and it ran and drove, just had no gauges and no 4th gear. Is there a pulling my hair out emoji

 

I think your instrument cluster is bad.

Just an educated guess though

 

Stev: Ground Strap looks good, don't see any fusable links.

You both mentioned the cluster, but regardless of the combination of the two clusters and the two pcms I have, I get the same no bus indicator in the odometer (and the same trans temp and o/d off lights after it warms up a little bit) and everything else works fine. Unless you know something I don't know about clusters, I'm inclined to think it's something else I haven't replaced or tested.

 

From my experience after throughly double and triple checking components and or a wiring repair(s) and multiple problems still exist expecially strange problems that seem to have no obvious rhyme or reason many many times it has been a ground issue. Ram vans are one of my favorite vehicles but in New England as these vans age corrosion is a serious problem which wrecks havoc with under hood/body grounds.

About 12 years ago I chased my tail for 3 days when we were returning from a trip to the mid west towing a trailer it was a nightmare and ultimately traced to a bad ground.


It can not hurt to go under your hood/van body to remove clean every ground that you can find even if it appears good with a stiff wire brush then reattach expecially the ones attached to the painted body panels it costs nothing but time.

Good luck.

 

Just to make sure...have you tried testing your new cluster?

You press and hold the odometer reset while the van is off. The turn the key to on. The cluster will test all aspects of itself and will error if bad.

iodj--grounds is a good place to start too - I agree. This guys poor van reminds me of the flood vehicles after Katrina/Wilma etc...they act the same way

Also, Ramz, you may just want to find your good 'ol local independent tech that has a DRB scan tool so you can see exactly what communications are going on. Then you can pinpoint the issue. When you get into situations like this, throwing parts at the problem and guessing is futile.

 

Yes I must 2nd funfair02 just replacing parts will definitely do two things lighten your wallet and frustrate you.

 

Thanks guys! I agree, a proper diagnosis is the way to go (also i have no more ideas of parts to replace ) I'll spend my next garage day cleaning grounds and if that turns up nothing I guess I'll hunt for an affordable scan, I too would like to see what the PCM sees. My outdated and generic EASE Scan Tool software does not read trans temp and certain other mfr specific information.

funair02 - I only had done a cluster check on the original cluster, didn't think about trying it on the second one but I'll do that first.

Do to an unexpected death in the family I have been unable to spend any time on this but will be back in a few days with updates. Thanks again for all the ideas!

 

it turned out that my search for a PCM reman was complicated by the fact that it was very specific to the year/VIN that I had, and only one out of three online venders actually HAD that specific part number. I called the third vender and after I told him the VIN he told me the part number of the exact PCM I was looking for. I ordered it and received it 5 days later.