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Richard
Richard, Dodge Technician
Category: Dodge
Satisfied Customers: 4011
Experience:  Over 22 years of experience as lead tech and shop foreman.
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1998 dodge ram 2500: v-10..disconnect..battery terminal..transmissions

Customer Question

I have a 1998 dodge ram 2500 with a v-10 with a 47re transmission. Just replaced the transmission this weekend. The sequence was disconnect the neg battery terminal and then start to take out and replace the transmissions. All went well until we re-connected the battery and tried to start the truck. The truck turned over but no fire or fuel. We thought that the fuel pump had failed, but we jumped the relay and the fuel pump worked but no fire when we tried to start it again. We tried to use a diagnostic tool and found out that the computer would not communicate with the tool. Found out that the cigarette lighter circuit powers the computer and it was intact and working. When trying to start the truck the fuel gauge does not move from empty. There is a least 10 gallons in the fuel tank. We cleaned all the battery terminals, checked for crimped wires around the bell housing and didn't find any. We are at a loss.
Submitted: 3 years ago.
Category: Dodge
Expert:  Richard replied 3 years ago.

Hello and welcome to Just Answer!

It sounds like there is something taking the PCM down! Can you disconnect the 8 way round solenoid connector from the transmission and see if the engine will start?

Let me know!

Customer: replied 3 years ago.
The truck is in a Hobby Sop and will be open on Thurs. I will try then. When we tried to start the truck and put a test light on the cigarette lighter fuse it was being drawn down and the light would fade. Is that an indicator?
Expert:  Richard replied 3 years ago.
Just make sure you charge the battery so it's fully charged before testing. The test light should dim a little when you go to start it, but not that much! That is telling me the starter is drawing too much current or the battery is weak.
Customer: replied 3 years ago.
The battery has been low. We have charging it off and on. Once we get the truck running will get a new one.
Expert:  Richard replied 3 years ago.

Let me know when you are ready to do some testing and I will help you solve this!

Thank you,

Richard

Customer: replied 3 years ago.
I removed the 8 pin plug in on the transmission and the truck didn't start. I cleaned the connections and re-connected the plug-in and it still did not start. The battery is not holding a charge and is having to be charged periodically. Is this a PCM issue? Do I need to get another one? I have to get this truck moved out of the Hobby Shop soon. I do not want to take it to a shop because they will be doing the same thing I am.
Expert:  Richard replied 3 years ago.

Does the starter crank the engine over good like before or does it seem like it drags and the engine turns over slow?

 

Can you take a voltage reading of the battery and then try and start your truck and see what the voltage drops to? I would like to know what the battery voltage is before and during cranking!

Customer: replied 3 years ago.
Once we charge the battery it cranks good. But something is draining the battery when we are not working on it. I went yesterday to start it after I unpluged the connection and it was dead.
Expert:  Richard replied 3 years ago.
Can you install a known good battery and fully charge it so we can do some testing?
Customer: replied 3 years ago.
Why won't the pcm talk to the diagnostic device? I feel the new battery would be a waste, because it get discharged.
Expert:  Richard replied 3 years ago.

The PCM won't communicate with the scanner because either the 5 volt sensor supply is going down or the PCM is faulty. The PCM sends out a 5 volt reference to sensors like the crank sensor, cam sensor and etc and when this voltage gets shorted to ground, the PCM will get taken down and the fuel & volt gauges won't work and the PCM won't communicate with a scan tool.

 

When would you have time to run through some tests with me? I am a full time tech during the day, but will be online this evening and tomorrow.

Customer: replied 3 years ago.
So we need to find the short before replacing the PCM. What tests do you recommend?
Expert:  Richard replied 3 years ago.
Can you disconnect the throttle position sensor wire and turn the key on, then test the voltage on the violet/white wire and let me know what you have.
Customer: replied 3 years ago.
We pulled all the fuzes one at a time and turned the key to see which system was drawing power from the battery. All test were conducted without the starter system plugged in. Nothing was discovered. Will try try your test tomorrow.
Expert:  Richard replied 3 years ago.

If you have no draw on the battery, then the battery must be faulty and won't hold charge.

 

The best way to check for draw is by using a amp meter in series with the battery cable and post, it doesn't matter which cable.

Let me know and we can go from there!

Customer: replied 3 years ago.
Relist: I still need help.
I checked the voltage at the speed sensor at the tails shaft. No voltage. I also checked the draw from the battery and it was .9 amps. I also bought a new battery, but I haven't installed it yet. Would the battery make that much of a difference.
Expert:  Richard replied 3 years ago.

I asked you to check the voltage at the throttle position sensor violet/white wire, not the speed sensor voltage!

Did you check that wire for voltage with the key on?

Customer: replied 3 years ago.
The voltage draw on the battery was with everything off. The speed sensor with the key on. The throttle position sensor is very hard to get to. Is the battery going to make a difference?
Expert:  Richard replied 3 years ago.

If the starter cranks the engine over good, then the battery is likely ok for testing.

Lets see where the draw is coming from. Hook up your amp meter and watch it as you pull all the fuses out one at a time. Once you pull one out and the draw doesn't change install that one and move to the next until you find the one that drops the current draw. Start with the interior fuse box first! You will have to wedge something in between the door and the door ajar switch near the door hinge so the button stays pressed in while you check this.

Customer: replied 3 years ago.
Do I conduct the draw on the battery terminal and the disconnected cable?
Expert:  Richard replied 3 years ago.
Yes, disconnect the battery cable(either one) and put your meter in series between the cable and post and make sure you have your meter on 10 amp scale and your leads are in the correct spot on the meter! If your meter shows a negative reading reverse the leads.
Customer: replied 3 years ago.
I will do the test on monday. Thanks for the directions.
Expert:  Richard replied 3 years ago.

You're welcome!

Remember not to open the doors or turn any accessories on while your meter is hooked up, you could burn the fuse in your meter if you do.

Customer: replied 3 years ago.
Relist: I still need help.
Customer: replied 3 years ago.
Check the draw of the battery and it was 0.005 amps. Took out all the fuses in the cab, shut the door and the draw was the same. Took out all the fuses under the hood and the draw was the same. Did the same with the relays, the same. Installed a new battery also. Tried the PCM communication, nothing. I have all over the bell housing for pinched wires or loose connections - nothing. Took the air filter assembly off to look behind and all looked good. I do not know what else to do. Please advise.
Expert:  Richard replied 3 years ago.

0.005 amps is only 5 milliamps and won't kill a good battery in a couple months. It would take a long time to kill a battery at only 5 milliamps. I thought you said it was .9 amps draw, what were you using to check that?

 

The PCM is down so we need to check the PCM for power and grounds.

Do you happen to have a 12 volt sealed beam headlight or bulb kicking around? We need to load test all the power and grounds to the PCM.

Customer: replied 3 years ago.
Explain how.
Expert:  Richard replied 3 years ago.

We need to remove the C1 connector from the PCM which is the connector closest to the engine. The PCM is on the pass side firewall! Hook the bulb up according to my picture for checking power then to check for ground move the wire from the negative post to the positive post.

Check terminal #2 light green/black wire for key on power.

Check terminal #22 red/white wire for battery power.

Check terminal #31 & 32 black/tan wires for ground.

Let me know what you find!

graphic

 

Customer: replied 3 years ago.
It might take me a few days because the hobby shop is closed on tues and wed.
Expert:  Richard replied 3 years ago.
Sure no problem!
Customer: replied 3 years ago.
Relist: I still need help.
Customer: replied 3 years ago.
I did the analysis:
C-1 connector - terminal #2 - lights up with power on.
terminal #22 lights up with power on.
terminal #31 & #32 lights on positive

checked the crankshaft posioning sensor with the key on - no voltage with any wire.

Also checked the voltage at the cigerette lighter fuse when cranking W/O PCM being connected. The voltage went from 12 volts to less than 3 volts. Does this man anything?
Does this also mean the pcm is bad?
Expert:  Richard replied 3 years ago.

Can you measure the battery voltage while cranking the engine over and let me know what it reads?

Customer: replied 3 years ago.
I will do that tomorrow. Will checking the TBS tell us if the PCM is working? Can we also check the PCM connectors for the same thing?
Expert:  Richard replied 3 years ago.

Checking the voltage at the TPS won't really tell us the PCM is bad, it will tell us if the 5 volt reference voltage is down.

 

If you checked the 5 volt supply wire(violet/white) at the crank sensor for voltage and you got no voltage with the key on, then the 5 volt supply is down or the PCM is down!

 

I need you to turn the key on and check the battery voltage at the battery, if the battery voltage is around 12 volts, I would like you to double check the violet/white wire for power. If you don't have 5 volts, we need to start disconnecting all the sensors one at a time to see if one of the sensors is taking down the voltage.

 

Let me know when you are ready to do this and I will walk you through the tests!

Customer: replied 3 years ago.
I did check the voltage of the new battery yesterday and it was 12.6 volts. After that we checked the crankshaft position sensor.
Expert:  Richard replied 3 years ago.

I would like you to disconnect the transmission 8 way round solenoid connector and test the voltage at the crank sensor violet/white wire, you should have 5 volts and if you still don't get 5 volts, visually check the harness from the solenoid connector up to the engine to make sure the wiring isn't pinched, cut, or has a bare spot and is touching ground. If it all looks ok, I will need you to disconnect the camshaft position sensor and re-test the voltage to the violet/white wire at the cam sensor connector. The camshaft position sensor is located on the timing chain case/cover on the left-front side of the engine. You should have 5 volts and if you don't disconnect the throttle position sensor, then the map sensor and let me know the results.

Customer: replied 3 years ago.
Today with the key on we tested the crankshaft position sensor, camshaft, tbs and the map sensor. None of them had any voltage. Then we disconnected the 8 connector plug at the transmission and checked all the sensors again and still nothing, no voltage. I would say the pcm is bad. Please advise.
Expert:  Richard replied 3 years ago.

Yes, the PCM has failed! Since you checked the harness that runs down to the transmission for short to ground on the orange wire and no short found, the PCM must have failed. To make sure the harness is ok, you could cut the orange and violet/white wire a few inches away from the PCM and then turn the key on and measure the voltage on those wires on the PCM side. This would rule out a short to ground on those wires. After testing those wires re-connect them using a non insulated butt connector, crimp, solder and heat shrink the connection.

Thank you,

Richard

Richard, Dodge Technician
Category: Dodge
Satisfied Customers: 4011
Experience: Over 22 years of experience as lead tech and shop foreman.
Richard and 11 other Dodge Specialists are ready to help you
Customer: replied 3 years ago.
Thanks, XXXXX XXXXX that . Do you have any reliable sources for PCM's.
Expert:  Richard replied 3 years ago.
Could I get the last 8 digits of your vin? I would like to look up the part number.
Customer: replied 3 years ago.
wj169549
Expert:  Richard replied 3 years ago.

The oem part # XXXXX 56046359AA and it changes up 6 times from the original #. Here are all the numbers that will work n your truck! 56046359AA, 56046359AB, 56046359AC, 56046359AD, 56046359AE, 56046359AF and R6046359AF. If you want to check on a used PCM, it can have any of those numbers.

Here are some sites that might have the part, The first one is a used parts locator and the nest two are new parts locator.

http://www.car-part.com/

http://www.moparonlineparts.com/

http://www.chryslerpartsonline.com/

I hope this helps!

Thank you,

Richard

Customer: replied 3 years ago.
Thank you I will pursue the part through your links.
Expert:  Richard replied 3 years ago.

You're welcome, let me know how you make out!

Thank you,

Richard

Customer: replied 3 years ago.
Instead of cutting the wire can we check the pin in C-1?
Expert:  Richard replied 3 years ago.

Yes you can, but you will need to check for continuity to ground on those to wires. You will need to disconnect all three PCM connectors and then set your meter to read ohms and put one lead of your meter to the orange wire and the other lead to ground. You shouldn't get any reading on your meter(open). Repeat test for the other wire.

Thank you,

Richard

Customer: replied 3 years ago.
Which pin number is the wire on the pcm connector and which pcm connector is the wire on.
Expert:  Richard replied 3 years ago.

The violet/white wire is in pin # 17 of the c1 connector(closest to the engine)

The orange wire is in pin # 31 in the c2 connector(middle).

Customer: replied 3 years ago.
We will give it a try on Monday.

Thanks
Expert:  Richard replied 3 years ago.
Let me know how you make out!
Customer: replied 3 years ago.

When all sensors were disconnected there were no reading on the C-1,C-2 pins.

However, when all the connectors were connected back we got a reading on the C2-31 of 2M ohms.

Expert:  Richard replied 3 years ago.

It is normal to see a reading like that with all the sensors connected. That is a very high resistance, so there is nothing to be concerned about that. You will need a PCM, we have throughly checked everything possible!

Let me know how you make out!

Thank you,

Richard

Customer: replied 3 years ago.
Thanks, I will order a pcm.
Expert:  Richard replied 3 years ago.

You're welcome!

 

Customer: replied 3 years ago.

Last Friday I installed the computer in the truck and it fired up. Thanks,

 

Steve

Expert:  Richard replied 3 years ago.

That's great, I'm happy to hear that!!

Thank you,

Richard

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Richard
Richard
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Over 22 years of experience as lead tech and shop foreman.