2001 24v Cummins High Idle Issue

[DanTheMan]

Guys I am at a loss. I HOPE someone can help me, this is frustrating.

 

Bought my first 24v Cummins, it’s an 01, 3500 dually, and 5 speed nv4500. 

 

She fires up beautifully, idles normally. Then it gots warm and it idles up, stays around 1500rpm or so.

 

The tachometer isn’t working, I tried replacing the camshaft position sensor and it didn’t fix the tachometer, maybe communication issue? 
 

Does the CPS have anything to do with idle? OBD2 computer says idling at 1500rpm.

 

The APPS sensor was replaced, and voltage set. Stays below 0.50 volts, around .44-.48.

 

According to the sensors live data reading, the voltage is all over the place for the other sensors too, the apps sensor is fluctuating bad, between 0 and 5v, and same with other sensors that are sensitive to voltage.

 

I just redid the four battery terminals, grounds were in horrible shape, but the other ends going to the block and chassis are healthy.

When I put a voltage meter on the APPS, I get very small fluctuations from .44 to .48, but the live data is freaking out.

 

Things I’ve done:

1. Calibrate APPS with Multimeter on the orange/black wire coming, while setting voltage.

 

2. Checked alternator, it is consistent and I couldn’t find any alternating current in the system. (Unless I need an oscilloscope to see this?)

 

3. Checked all connections, the ECT sensor, the ground straps, everything.

 

4. Replaced IAT sensor

 

5. Replaced CPS..

 

Edited Wednesday at 05:16 PM by DanTheMan

[Tractorman]

2 hours ago, DanTheMan said:

According to the sensors live data reading, the voltage is all over the place for the other sensors too, the apps sensor is fluctuating bad, between 0 and 5v, and same with other sensors that are sensitive to voltage.

 

Have you checked for any trouble codes? 

 

The oil pressure switch, camshaft position sensor, and the manifold absolute pressure sensor all receive a 5 volt signal from the ECM.  Splice #165 (S165) is a through connection for ground for all of these sensors and oil pressure switch. 

 

Since voltage is "all over the place" for some of these sensors, I would be checking the source and ground for the 5 volt supply.

 

- John
 

 

[DanTheMan]

Thank you, @Tractorman, I will check that out! Thanks for the diagram.

 

The grounds have been all messed up on this truck so I’m hoping that I can find that connection point and that would be my problem.

 

If it turns out the ECM is not delivering a consistent 5 V signal, can I put a 12 V to 5 V DC converter and supply power for all of the sensors? 
 

I am assuming that the three wires on the sensors, one is for ground, one is for reference voltage and the other is a signal going to the ECU, is returning voltage back to the ECU?

[DanTheMan]

So I found an interesting problem…

 

I heard a ticking sound, there is some arcing going on every few seconds. Now to find the culprit, I have no idea where to start. I’m assuming a wire rubbed raw and it is shorting against the block, or bracket. Any ideas where I should start? Specifically arcing by the harmonic balancer. Here is the link below to the YouTube video showing it. Considering it’s arcing every few seconds, I’m going to assume it’s coming off of the ECU and it’s self resetting, hence no blown fuses. 

 

YOUTUBE: ENGINE ARCING

 

[Tractorman]

4 hours ago, DanTheMan said:

Specifically arcing by the harmonic balancer.

 

I have never experienced this, but I have heard of it happening.  The general consensus is that a strong static charge builds from the normal operation of the serpentine belt.  That static charge discharges periodically near the crank pulley because the crank pulley has the shortest air gap distance to ground.  Some have replaced the serpentine belt with a different brand and said that it cured the issue.  Others have said that the sparking causes no harm and have done nothing to stop it.

 

- John

7 hours ago, DanTheMan said:

If it turns out the ECM is not delivering a consistent 5 V signal, can I put a 12 V to 5 V DC converter and supply power for all of the sensors?

 

I don't think it is that simple.  The ECM could be putting out a good 5 volt supply, but an erratic ground could make it look like an erratic 5 volt supply.

 

I would try to figure it out - not bypass it.

 

- John

 

Edited 23 hours ago by Tractorman

[DanTheMan]

I was able to inspect the harness, and the brackets that bolt the harness to the block and to the frame have all been undone… I don’t think these ground the harness in anyway, as they spin freely around the harness and nothings connected to it. I will be working on reattaching everything properly once I figure out the issue.

 

However, I did check every possible sensor, and on one sensor, I checked the 5v power (orange wire off of the IAT) to ground and it showed very consistent 5 volts. No fluctuations.

 

It is my understanding that if I disconnect the APPS and it was the problem, it should revert to an idle, the voltage is consistent on the APPS as well.

 

I may just completely remove the harness and just go through the whole thing entirely. I’m starting to lose patience with it lol

[Tractorman]

11 hours ago, DanTheMan said:

I checked the 5v power (orange wire off of the IAT) to ground and it showed very consistent 5 volts. No fluctuations.

 

When you saw a consistent 5 volts at the IAT, were you using the black/tan wire for ground, or were providing a remote ground?

 

- John

[DanTheMan]

@Tractorman, I honestly used a remote ground.. Not sure why I didn’t think to use the ground coming off the connector. Wow. That was a brain fart. You’d think being a licensed electrician I’d have thought of this… 

 

I will do so later tonight when I get off of work, thank you! I’m probably going to replace the MAP as well just because.

 

I suspect this is not the original motor because everything connected to the block harness wise was not connected, I’m going to be removing the front clip this weekend so I can really get in there to fix any possible areas for the harness to rub.
 

Side note, I need to do the timing gear cover anyway as it’s leaking pretty bad, and also need to put a bracket over the killer dowel. Someone mentioned that to me this morning actually.

 

I really do appreciate your help.

 

[Tractorman]

Splice #165 is a crimped affair - not the best idea for a quality electrical connection.  It is located near the timing gear case on the driver side of the engine.  Below is a link to the W-T ground reference mod that would be in your interest to perform.

 

- John

 

 

[DanTheMan]

@Tractorman, I have had a few hours to play with the truck, and I noticed a few things on my new scanner that I received. My scan shows a boost pressure of 13.2 PSI even when the truck is off. I unplugged the MAP sensor and it suddenly read 0.00, however, I do have two boost pressure graphs on tablet, one shows 1.9 psi and the other one shows 13. Not sure why there are two. 

 

Would this cause the idle to increase as well? Or is that just simply for reading boost pressure? Perhaps I’m still dealing with a ground issue and it’s causing the sensors to go haywire, but it was consistently showing 13 psi even with the truck off.
 

I removed the entire conduit off of the harness and finally found the crimp connection, it was further underneath the diesel filter on the side of the block underneath the ECU.

 

There is one other important thing I should note, the inside of this conduit and the cloth wrapping, as well as all of the wires were absolutely soaked in diesel, fuel, and motor oil, so I decreased everything and will continue to work on it tomorrow.