Engine/Transmission (1998.5 - 2002) 2001 24V no start — electrical power issues

[JHenry]

Gordon.

Should you need to buy from EBAY, I have a Pay-Pal account and would be glad to buy it for you and have it shipped to your address. You could reimburse me with a check. I've been a subscriber to your Power Wagon Advertiser magazine long enough to feel like I know you.

Jerry Henry

 

[Gordon Maney]

Gordon.
Should you need to buy from EBAY, I have a Pay-Pal account and would be glad to buy it for you and have it shipped to your address. You could reimburse me with a check. I've been a subscriber to your Power Wagon Advertiser magazine long enough to feel like I know you.
Jerry Henry

Thank you, Jerry!

 

[Gordon Maney]

It suggests that there could be a break in the wiring somewhere between fuse #3 in the PDC and the ECM connector. You'll have to troubleshoot the wiring harness by checking for 12 volts at various points along the circuit until you find where it stops.

See the attached schematic from the Dodge service manual of the circuit which runs from the battery all the way to the ECM connector. Since you've already verified you have power at fuse #3 in the PDC, you can start your search after that point. Also, since you don't have power at either socket #48 or #50 at the ECM connector, it's probably safe to assume the break is before splice 167 (listed as S167 on the schematic). So by process of elimination, the break will most likely be between fuse #3 in the PDC and splice 167.

The suspect culprits for a break location are joint connector #2, which is inside (under) the PDC, connector 130 (listed as C130 on the schematic), splice 161 (S161), and connector 125 (C125).

I'd recommend beginning your search toward the ECM end of the circuit and work back from there. Note that according to the schematic, the wire in this entire circuit is Red with a White stripe. Keep this is mind when you're trying to find the correct pins to check on the connectors.

S167 is located in the wiring harness bundle after C125 adjacent to the lift pump on the side of the engine (if you have one). I'd skip worrying about finding this splice (unless you have to later) and move on to C125.

C125 is an 11-pin connector located on the firewall at the rear of the engine. You're looking for pin #3 there. A pinout diagram is attached. Keep in mind the mirror image issue you've already learned about when reading pinout diagrams. I'd check to see if power is present at the PDC side of this connector by disconnect it, or by back probing the connector using a paper clip inserted alongside the wire where it enters the connector. If you find power here, then the break must be further up the circuit toward the PDC.

Next comes S161, which is located in the wiring harness bundle leading between the PDC and C125. As before, I'd skip worrying about this splice for now and move on to the next connector in the circuit.

C130 is the large squarish shaped 42-pin connector located in the right rear corner of the PDC after you take the cover off. According to the schematic, you're looking for pin #3 there also. A pin diagram is attached. Disconnect C130 and test to see if you have power at pin #3 on the PDC side. If you do, you'll have verified joint connector #2 inside the PDC is fine. Reconnect C130 and try back-probing pin #3 with a paper clip to see that power is getting through the connector.​

Please let us know what you find.

John L.

I discover that the red and white lead coming from the PDC is hot. The PDC side of it is hot at C125, and the downstream side of that connector set is hot at that terminal. One interesting side note... . it is not red and white on the downstream side, it is orange, I would say. I don't see that the harness is in any way disturbed or modified, so I would say that was original, even though the diagram says it remains red and white on that side.

It may be S167, or wire somewhere between C125 and the ECM connector.

I gather I really need now to open up that entire harness section so I can see all the wires. Do you agree?

 

[JLandry]

Regarding C130, I had been studying it prior to reading your post. Is that disconnected by loosening the capscrew [displaying a phillips screwdriver feature] visible from above?

Correct.

Regarding the joint connector 2 under the PDC, that would be visible by removing fasteners that hold down the PDC?

That I can't help you with as I've never tried to take the PDC apart. The service manual states it's intended to be replaced as a unit and gives no disassembly instructions. The service manual does show a diagram which seems to indicate joint connector 2 is located in the left rear corner of the PDC, directly opposite C130. Since joint connector 2 isn't visible when you pull the lid off the top of the C130, it must be underneath the layer holding the fuses and relays.



I'd avoid trying to disassemble the PDC unless you're absolutely sure you have a break inside and you have no other choice but to do so. There are a lot of critical circuits running through the PDC and you could make the electrical problems a lot worse if you screw something up. Instead, if you do have a break in the PDC, I'd recommend fabricating a new auxilary wiring harness (containing an appropriate sized fuse) to bypass around the PDC (abandoning the faulty circuit within) and connect it into the wiring harness somewhere after the PDC and ahead of C125.



John L.

 

[JLandry]

It may be S167, or wire somewhere between C125 and the ECM connector.



I gather I really need now to open up that entire harness section so I can see all the wires. Do you agree?

I would agree that this seems like a logical next step, but are you absolutely sure you're truly not getting power to pins 48 and 50 of the ECM connector? Maybe you should re-verify you're probing the correct pins on the ECM connector by checking the wire colors?



If you're definitely not getting power to the ECM connector, then start peeling apart the wrapping on the harness starting at the ECM connector. Check for power every few inches along the wire by piercing the insulation with your test light probe (watch your fingers). Sooner or later you're going to find out where the power ends!



Good luck,



John L.

 

[Gordon Maney]

Here is an interesting thing. The phillips head capscrew at C130 was loose. It also cannot be tightened. I am not sure what to make of that, although given my test light behavior at C125 it does not matter [?].

I did try 48 and 50 several times, including with a paper clip. I can also try them again, but am pretty sure they are not live.

 

[JHenry]

[

If you're definitely not getting power to the ECM connector, then start peeling apart the wrapping on the harness starting at the ECM connector. Check for power every few inches along the wire by piercing the insulation with your test light probe (watch your fingers). Sooner or later you're going to find out where the power ends!



Good luck,



John L. [/QUOTE]



Would it be possible to use a tester to check for continuity, rather than piercing the insulation so much? JH

 

[JLandry]

Would it be possible to use a tester to check for continuity, rather than piercing the insulation so much? JH

A valid concern, but since he's already tested the circuit to the last accessible point (a connector on the firewall) prior to the suspected break, there's little choice left but to pierce the insulation along the remaining wire with his test light or multimeter. Considering the alternatives, I think this is probably the best choice. But I'm always open to better suggestions!



John L.

 

[Sticks]

[



Would it be possible to use a tester to check for continuity, rather than piercing the insulation so much? JH

Continuity can give false readings. A wire filament no thicker than a spiders strand of web will give 100% continuity, but will not conduct sufficient power for a test light or maybe even a DVM.

A valid concern, but since he's already tested the circuit to the last accessible point (a connector on the firewall) prior to the suspected break, there's little choice left but to pierce the insulation along the remaining wire with his test light or multimeter. Considering the alternatives, I think this is probably the best choice. But I'm always open to better suggestions!



John L.

I concur, time to triple check to make absolutely sure you have tested the correct wires at the computer connection, go back to the last known junction or connector where there was power, triple check that you are probing the correct wires, and start tracing the wire looking for a break or burn through heading towards the PCM.



RE: C130 - if the connector is tight even with the cap screw loose, then I'd not worry about it. This is one of those "I'd have to see it, touch it to be sure".

 

[Gordon Maney]

Do I dare spray electromotive cleaner into that ECM connector? Brakleen would degrade rubber and plastic, but I am thinking electromotive cleaner would not. Thoughts on that? The connector, along with the other one we discussed, shows the presence of dielectric grease. I consider cleaning it and regreasing it.

 

[JLandry]

Do I dare spray electromotive cleaner into that ECM connector?

Gordon,



Unless there's something making you think the connector is dirty and not making good contact, I'm not sure I would bother at this point. But if you were to use a true contact cleaner (not carb or brake cleaner, etc. ) and then reapply some dielectric grease, it shouldn't cause any problems. Just be sure and let the contact cleaner dry before reattaching the connectors... it does evaporate rather quickly though. In no circumstances spray anything into the ECM socket... that's asking for trouble!



Any progress on finding the location of the open circuit?



John L.

 

[JLandry]

Continuity can give false readings. A wire filament no thicker than a spiders strand of web will give 100% continuity, but will not conduct sufficient power for a test light or maybe even a DVM.

Excellent point. I have to remind myself of this when troubleshooting wiring.



Thanks!



John L.

 

[Gordon Maney]

Gordon,

Unless there's something making you think the connector is dirty and not making good contact, I'm not sure I would bother at this point. But if you were to use a true contact cleaner (not carb or brake cleaner, etc. ) and then reapply some dielectric grease, it shouldn't cause any problems. Just be sure and let the contact cleaner dry before reattaching the connectors... it does evaporate rather quickly though. In no circumstances spray anything into the ECM socket... that's asking for trouble!

Any progress on finding the location of the open circuit?

John L.

No progress yet, I have been delayed from that for now, and may not be able to get back to it until tomorrow.

Regarding the ECM socket, you are meaning the liquid might get inside the unit?

I will say I have a good feeling about having it narrowed down to such a seemingly small run of harness.

A remaining question, of course, is..... will correcting this issue fix the truck? I am inclined to believe it will, but admit to some terror yet.

 

[JLandry]

Regarding the ECM socket, you are meaning the liquid might get inside the unit?

Exactly. While in theory it shouldn't hurt it, you don't want to risk it.

A remaining question, of course, is..... will correcting this issue fix the truck? I am inclined to believe it will, but admit to some terror yet.

That's what we're hoping for.



Based on the fact that power is not present at pins 48 and 50 of the ECM connector, the symptoms (truck not starting, lift pump not being energized, PCM not hearing from the ECM), all seem consistent with the ECM simply not receiving power. Hopefully when you fix the power supply problem everything will be back to normal.



If / when the engine does start, possibly you'll have some trouble codes stored in the ECM and PCM from all this which you'll need to clear. Don't be alarmed if that happens... it's perfectly normal.



Regards,



John L.

 

[Gordon Maney]

I now have a lot of the harness unwrapped. I was wrong on the color. It is orange with a green tracer. It is hot as far as I have gotten so far, and I have gone quite a ways.

Still looking... .

 

[JLandry]

I now have a lot of the harness unwrapped. I was wrong on the color. It is orange with a green tracer.

That's interesting. In looking over all the circuits in the service manual which pass through C125, none of them are shown as being OR/GR. There is an OR/DB listed though. That's for the APPS signal and shouldn't be hot with the ignition key off. No matter, it wouldn't be the first time a service manual had errors.



By chance have you thought to check the color of the wires leading to pins 48 and 50 at the ECM connector? Logic would dictate they should be the same OR/GR you're seeing coming out of pin 3 at C125.



John L.

 

[Gordon Maney]

Based upon what I have seen thus far, I don't believe they are, and don't believe any wires at that end are that color.

 

[Gordon Maney]

The process of discovery continues....

Yes.

If you find 12 volts are indeed present on one side of the socket for fuse #3 in the PDC, and you've verified the fuse is good, then reinstall the fuse and perform the following checks:

1. With the ignition switch OFF, disconnect the 50-pin connector from the ECM.
2. Using your voltmeter (or a test light), verify 12 volts are present at socket numbers 48 and 50 of the ECM's 50-pin connector. Use a straightened paper clip inserted into the socket if your voltmeter probe is too wide to enter and make contact down in the sockets. These two sockets are supposed to provide 12 volts to the ECM at all times (when the vehicle batteries are connected obviously).
3. Next turn the ignition key to the RUN position.
4. Again using your voltmeter (or a test light), verify you have 12 volts present at socket number 5 of the ECM's 50-pin connector. When 12 volts appear at this socket, the ECM turns on.
5. Turn the ignition switch OFF and reconnect the ECM connector.​

If these checks pass successfully, then it's pretty safe to assume the ECM is toast. If any of the checks don't pass, then you probably have a wiring problem which you'll need to investigate further.

Please keep us posted.

Good luck,

John L.

#ad

I had been working steadily at the tedious matter of opening up the wiring harness, careful to not cut wires with the razor blade and X-acto knife as I cut the tape closing the raceway.

The farther along I got, the more difficult it became, and that with all leads rearward disconnected from their points of connection and the fastening strap disconnected from the mounting point near the previous location of the lift pump. You can only pull so much harness up out of there and then can't get both arms in the available space.

Perhaps I was following intuition, or simply on the edge of a good whine; in realizing the wires continued to be hot as far as I went — including after S167 [which is plainly marked with characters on a shrink sleeve, for those interested in that bit of trivia] — I started to worry I would get the entire thing untaped and the wires would be hot to the end at the connector.

My mind was churning through that. I tried the connector testing again, using a paper clip again, and there was no voltage again.

I went back in the house to study the drawings. Realistically, I may have gone in the house to escape. I was looking at the connector in your post, and looking at the connector in my paper manual and in my .pdf manual I got on the internet recently [... . interesting that you can get that now for free] and discovered that the preceding image has six (6) rows of 60 pins, and the images in my manuals here had five (5) rows of 50 pins.

That meant I was not supposed to be probing the row next to the bottom, I was supposed to be probing the bottom row. [It also explains why I said the wires were not red... . ]

Testing socket holes 48 and 50 my lovely, new, Sears test light glowed a bright, happy red.

So, back to what you were saying, it passed all those tests, so the ECM must be toast. I am so excited this is resolved.

I have to admit, it would never have occurred to me that the pin count could be different.

Where is that page from that you posted? Mine is from page 8W-80-40. Both my paper manual and the .pdf manual are that page number. These are from the 2001 Ram truck manual, volume 1. The back cover says 81-370-1008, if that is meaningful.

Also, wires 48 and 50 are red with a white tracer, though the tracer is just about impossible to see.

 

[JLandry]

I... the preceding image has six (6) rows of 60 pins, and the images in my manuals here had five (5) rows of 50 pins.

Good catch and my sincere apology Gordon. That mistake is completely my fault. While trying to upload a picture of the ECM connector, the TDR forum software informed me the file already existed (presumably because I was using the same file name), so instead of uploading what I had, I grabbed the URL from the existing image to embed in my post and then didn't bother to look at it too closely. Just so you know, that's an image of an ECM connector from a 2003 model year ECM. Sorry for all the extra work this caused you.



The correct pinout is attached for anyone else who might read this thread someday.

So, back to what you were saying, it passed all those tests, so the ECM must be toast.

Yes... it's unfortunate but that would appear to be the case.



Best regards,



John L.

 

[Gordon Maney]

Good catch and my sincere apology Gordon. That mistake is completely my fault. While trying to upload a picture of the ECM connector, the TDR forum software informed me the file already existed (presumably because I was using the same file name), so instead of uploading what I had, I grabbed the URL from the existing image to embed in my post and then didn't bother to look at it too closely. Just so you know, that's an image of an ECM connector from a 2003 model year ECM. Sorry for all the extra work this caused you.

The correct pinout is attached for anyone else who might read this thread someday.

Yes... it's unfortunate but that would appear to be the case.

Best regards,

John L.

No need to apologize. Really. I am just happy I figured it out. I was a vocational automotive instructor for 16 years; I last served in that capacity in 1989. New experience is good, and it provided basis to think in new ways.