Monthly Archives: November 2015

Ram troubleshooting

I took the day off yesterday and worked on the Ram all day. I took the air intake completely off (and thus got my first opportunity to inspect the turbo — its blades look just fine and I couldn’t detect any shaft play, either side-to-side or in/out). The turbo looks good.

I took the passenger side battery box off so I could get at all the loom that runs underneath it, and then inspected the entire length of the fan clutch loom from the plug to where it joins other loom.

I was able to find a place, very close to the connector, that looked like it had been pinched. Two of the wires had wire showing through the insulation. So I cut out the bad section and soldered / shrink tubed in a new section of wire about two inches long. I replaced the loom, too. I hooked the fan clutch back up.

I took the batteries to Auto Zone and had them tested. One tested good; the other tested bad. Having read quite a few threads that say these codes can be the result of a bad battery, I replaced both the batteries with Wal-Mart Everstart Maxx 65s batteries, which have a five-year warranty.

I also cleaned and re-oiled the air filter.

And I took the top of the valve cover off and repainted it.

Unfortunately, this work doesn’t seem to have solved the problem. The truck started misbehaving again immediately upon startup, though the problem is not as obnoxious as it was before. I’m seeing the same codes, too (P0480, P0483, P1652).

Also, I used Torque to pull codes and got P1652, C1200, P00<D, B2TAE, ROR-, and C12<D. Except for P1652 (and maybe C1200), none of these make any sense. But then, Torque was complaining about a possible error communicating with the ECM. I hope that doesn’t mean the ECM is the actual problem. Though it would be an easy fix, it wouldn’t be cheap.

… well, okay. I guess I can get a plug-and-play ECM on eBay for $550, excluding core. So that’s not too horrible if I have to go that route.

I drove the Ram to work this morning (I’m patching production servers on a Saturday) and although the CEL came on a few times, the gauges didn’t misbehave and there was no dinging at all.

Ram gauges going nuts again

Once it turned colder, the dash gauges started acting up again, going dead, lights flashing, etc. I was getting codes P0480 and P0483.

I made a weather front out of a cardboard box and put it between the radiator and the condenser, and disconnected the fan clutch.

Disconnecting it made no difference. Everything is still going crazy. So, at least I can be reasonably confident there’s nothing wrong with the fan clutch; that’s $350 I don’t need to spend.

And this morning I got the code P1652, indicating the J1850 bus is shorting to ground somewhere.

pwong on the Cummins Forum linked a diagnostic procedure for this code that should isolate it from a bad ECM. Either the problem is caused by a bad ECM, or by a short elsewhere (or possibly in another module that is connected to the ECM via the J1850 bus).

I hope it’s not the ECM; they’re not a cheap replacement.

He also linked to three documents which serve as a schematic of the J1850 bus on my truck: 1, 2, 3. I’ve got these same schematics in my 03 Dodge Ram Service Manual, by the way.

The steps are:

  1. Eliminate the ECM as a source of the problem.
  2. Eliminate wiring shorts as a source of the problem.
  3. Eliminate every module connected to the bus as a source of the problem (by unplugging all modules and then plugging each one back in, one at a time, until the problem recurs).

The upshot is that I have to go through the entire engine compartment, checking all the wiring and modules, one-by-one. Hopefully I can find something obviously wrong.