I am new here to the site, but I am having an issue with my Dodge. I had some issues starting my truck, when I turned the key over lights would come on and truck would start but showed no voltage, and abs/ parking brake lights on and gauges showed no voltage or tach, oil pressure nothing. Next time it would just click when the key was turned over, tried again a few times and it started. So I decided to test my ignition switch and found it to be bad, no voltage when the key was turned to start. Fixed the starting problem or at least i thought so. Now my GEN light is on, wont shift out of first, and my voltage is staying at 12v until engine warms up to 180 degrees then, shifts 1,2,3 but GEN light is still on and voltage drops to about 8v. Alternator was replaced and checked, batteries were charged and load tested everything worked out fine once replaced, next day same issues. Now it wont start again, tested ignition switch again, and its bad...again..Any ideas? 

 

By the way the vehicle is a 1996 Dodge Ram 2500, 12valve Cummins, A/T, 4x4.

Edited January 14, 20178 yr by ohioboy

Crank sensor? Are you seeing RPM signal? 

 

Field leads is the blue wire seeing +12V with the key on? The green wire should be variable ground when the tach signal is seen by the PCM.

 

Check the air gap on the ess. Very common to get some dirt or debris blocking it.

Tach works just fine, think i might have it narrowed down to a ground issue, just havent quite figured out which side yet. I was stuck in snow up over my axles so I left it in the shop for three days to thaw completely then the problems began.

Edited January 18, 20178 yr by ohioboy

I went trough all connections to include grounds, all tested good so I put elec. Grease on all connections, pcm, and relays. As a last resort I pulled the plug for the crank sensor and what do ya know, corrosion...Green leprechaun ****! Cleaned the connection and dielectric greased that connection as well and what do ya know, fired right up and charged. I then let it run for about 20 min and expected it to have a gen light on and not charging as usual when I got back but the gauge was holding steady at 14+ volts .

It is always nice to find something.

Well it's official, I tested my crank sensor actions the contacts and I have resistance, therefore according to pro demand the sensor is bad, which explains the corrosion. Just weird that I had a tach?

Resistance is normal. Hall effect sensors typical have a coil inside with a magnet. So every time the tone wheel tooth pass it creates a sine wave. So if you put you meter on AC scale in the mV range you should see a AC voltage created. This is normal. I test brake speed sensors the same way.  

Well even though I found another faulty part, I changed out the ESS and still have the same symptoms. Anyone have any other ideas?

Would the battery temp sensor have anything to do with charging or where exactly does it get its signal from?

All the battery temperature sensor does is alter the charging voltage to meet the needs of the battery by temperature. So as the battery get warmer then the charging voltage goes down. All I can say is check for a error code for the battery temperature sensor. 

On ‎1‎/‎20‎/‎2017 at 7:49 PM, ohioboy said:

Well even though I found another faulty part, I changed out the ESS and still have the same symptoms. Anyone have any other ideas?

Since the symptoms come and go like that I would say it's not a component failure but a loose connection somewhere. I would try wiggle jiggle the wires and harnesses one at a time to see if you can make it work again or not work again. Someone watching the gauges while doing that may help you narrow it down.

So now it seems i have narrowed down a symptom and somewhat of a solution, correct me if I am wrong but to reset the PCM you must cycle the ignition on, off, on....ok that said, I started my truck today and let it run checking voltage, charging, batteries were at 12.29 cold, tested battery voltage from top of the terminals on both batteries. Voltage raised to 13.65 and slowly climbed after running 2 min .01- .02 v, lights, radio, and heater blower. I let it run to engine temp was around 160 and decided to take it for a drive. Made it approx 3 blocks, looked down temp @180 give or take, and my GEN light was on and voltage slowly dropped to around 11-12v. Got it back to the shop, turned it off and cycled the key to try and get some possible CEL codes but nothing, I did notice that my voltage was back up to over 12 according to the gauge, so I started it and watched the voltage climb up to almost 14v for about a min and then GEN light comes back on and voltage drops. It did this exact thing three times in a row.

There is a number 8 gauge wire coming off the passenger battery that hangs down somewhere down below between the battery and the alternator. It has a light grey factory connector on it and goes around the air box to the PCM. Sometimes that factory connector goes loose and does not fit snug. I would check that one.

 

Check the wire harness to the PCM make sure no corrosion and is plugged in nice and tight. Also check the PCM ground to the firewall next to the PCM. Sometimes the weather stripping for the hood right above the PCM allows rain to drip down around the PCM. So you want to check that too. I had missing weatherstrip so I had to make a small berm of caulking to redirect the water toward the passenger door and not drip on the PCM.

Is that a plug in connector under the battery? Or just some type of fusable link connection?

 

 

You'll find it. It's light grey connecting one conductor about number 8 gauge. It is a clip together factory connector with a spade connector inside. Unlock it and see if it's tight or loose when you pull it apart. Look for corrosion. It runs to the PCM. Don't forget the PCM ground to firewall toward drivers about 4-6 inches away.

I'll have to check that out tomorrow, my truck is currently at work, 40 miles away, so i have a place out of my current environment of -20 to work on it. could I bypass the plug connection and just use heatshrink connections to replace it or just clean, dielectric grease and leave it be?

 

well I have checked my grounds and im not finding any plugs under the passenger side battery, it only has a big cable running from neg to engine around block heater, and one runs to behind the battery on fender well.

well I have checked my grounds and im not finding any plugs under the passenger side battery, it only has a big cable running from neg to engine around block heater, and one runs to behind the battery on fender well. Also does anyone have wiring colors/functions of the cranksensor...ie signal wire, 5v wire, and ground?

 

Edited January 26, 20178 yr by ohioboy

Update-

Still no charge past 13.8 and seems as if my transmission is in some type of Limp mode. After driving a while, gen light comes on and begins to discharge. I am at a loss lol...