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 October 16 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 October 17 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.

[DanTheMan]

@Tractorman, I have discovered something else. When digging into the ecu harness, I discovered an electrical taped connection there. I undid it and found an Orange/black or brown I can’t tell, wire; and it connects to the shielded part of the gray signal cable, when it makes its way up to the back of the VP44, I have no idea where it’s supposed to connect. 
 

Any ideas? First picture shows the wire beside the ecu. The second shows up under the connector to the VP44.

[DanTheMan]

@Tractorman I have checked absolutely everything I could. Replaced fuel lift pump, replaced every sensor (two were actually bad), I replaced the alternator (Showing low voltage, under 12.10), I have checked the wiring, everything you said to check and nothing. I am beginning to wonder if it's a software issue, perhaps someone put a tuner on it, and increased the idle? No idea how to even check that other than buying a tuner.

I should also mention, that when I do a cold start, it idles normally.. After about 2-3 minutes, it'll increase to 1,000rpm. After that it gradually increases to 1200-1300rpm, and never drops back down, no matter how warm it gets.

I checked the coolant temperature sensor as well; that is working normally. I even put resistors on the connector to simulate a hot engine, still nothing.

I am at a total loss here; could the VP44 feed the engine more fuel than necessary at idle somehow?

[Tractorman]

I went back and re-read this thread.  If I am understanding correctly, the only problem you are now having is that the engine won't return to a normal idle rpm after the engine has warmed up.  Other than that, the engine is performing fine/  Is this correct? 

 

On 10/16/2024 at 10:15 AM, DanTheMan said:

the apps sensor is fluctuating bad, between 0 and 5v,

 

Is this still occurring.

 

Have you driven the truck with a scanner monitoring the APPS at idle after the engine has warmed and the engine rpms won't drop back to idle?  The scanner should read zero percent at idle, then start reading a small percentage just off idle.  The APPS uses an internal idle validation switch that tells  the ECM to let the engine idle.  When the ECM commands "idle", all other inputs to the ECM are ignored.

 

There is a procedure that involves disconnecting the electrical connector on the VP44's PSG and then jumpering a remote power and ground to the PSG.  In your case, if the warm engine idles normally under the jumpered conditons, this would indicate that the VP44 is operating as it should. 

 

The link below is for Blue Chip Diesel.  It shows various troubleshooting methods for diagnosing the VP44 fuel system.  Carefully read steps #2 and #3 for a  "No Start" situation.  If you perform Step #3 and the engine idles fine after it has warmed, then I would think you can rule out the VP44 as the problem.

 

https://www.bluechipdiesel.com/runningtests

 

Have you checked for DTC's?  I asked the question before, but I don't recall reading an answer.

 

Don't give up!

 

- John

 

Edited October 28 by Tractorman

[DanTheMan]

@Tractorman, Hey there thanks for the response! 
 

I have checked the voltage, no more fluctuations! After a while idling, it increases RPM, at that point the APPS shows zero percent when idling even when it revs up.

 

I will go ahead and look into the bypass to check the VP44..

 

The only error codes I noticed was from the PCM, for IAT sensor (I just replaced it, not sure why it’s acting up. But I’ll check it again.) and the APPS voltage too low/too high, but I was initially calibrating it too low or too high. Those have gone away since I’ve calibrated the apps correctly. I’ll double check later.

 

However I did see a P1693 code but that says it’s a “companion code”, I assume this is the Cummins ECU informing the PCM that there’s an error… How do I read those error codes? I’ve already tried the cluster method, it only shows the PCM error codes.

 

 

Edited October 28 by DanTheMan

[Tractorman]

Sounds like the APPS is performing as it should.  As far as reading codes, not all scanners are equal.  See if you can borrow a better scanner, or maybe try your local auto parts store for a free scan.

 

How many miles on the truck?  When did you take ownership? 

Has the improper idle symptom been there sine you owned the truck?

Do you know what injectors are in the engine and how many miles on them?

 

I assume that there is no tuner hooked up.  You mentioned that you think the engine has been replaced - any more information on that?

 

- John

[DanTheMan]

I have the TopDon Phoenix Lite, pretty much the best I can obtain that does virtually anything, it couldn’t access the error code either. I’ve tried one other scanner as well.

 

340,000 miles on the body, I “think” the engine has based off of the harnesses being undone, and just signs of being painted, like someone tried to clean and paint it before putting it in.

I purchased the truck a few weeks ago, with the idle issue. No idea on the injectors, no tuner either.

 

Although, I have been hearing a long beep when I disconnect and reconnect battery power, as if there’s a device somewhere, I’m assuming it’s a tracker that was installed years ago, and I can’t seem to locate it.

[Tractorman]

Your scanner certainly sounds more than adequate to pull codes. 

 

I would follow up with Blue Chips guidance to make the VP44 run as a stand-alone by supplying remote power and ground.  Wait to do this until the engine is fully warmed and you are experiencing the idle issue. 

 

In my mind, if the engine idles fine while jumpered under these conditions, then I would say the VP44 is fine, and the injectors are fine, but you could have a problem with the ECM or wiring (I know, you have thoroughly checked out the wiring).  The following is an excerpt from Blue Chip Diesel under "RPM takes off without throttle application".

 

"If it revs up on its own from an idle, you can also do the “No Start” test three, and if it idles smoothly and at the same speed dependably, then it means the ECM is the cause of the problem."

 

If the engine continues to run at a fast idle while jumpered, then I would say you could have a VP44 problem, or a problem with injectors.  Normally, I would not think the injectors could be an issue, but you do not know anything about the injectors that are currently in the engine.  It is possibly to have high mileage worn out, high horsepower injectors that could exceed the fuel rate control limits of the ECM when engine idle is commanded.  If the ECM cannot pull back fueling enough, then engine rpm's could begin to creep up.  Just a guess here.

 

Let me know what you think.

 

- John

 

 

[DanTheMan]

I will perform the test on the VP44 to see what I can come up with. I am about done being covered in fuel trying to fix these leaks tonight.

 

Could injectors still be the issue considering the truck starts up, and idles perfectly? I mean, it idles right at about 850rpm, and within 5 minutes it’s idling 1300+

The link below shows an odd thing I noticed. I never really revved it up before until now, like really revved it up. It seems to run great but starts to shake pretty good when approaching WOT and white smoke, smells like raw diesel. I’m really beginning to think the VP44 is the issue… I’m hoping not; but will perform those tests. 

 

 

 

 

 

 

 

 

[Tractorman]

2 hours ago, DanTheMan said:

Could injectors still be the issue considering the truck starts up, and idles perfectly? I mean, it idles right at about 850rpm, and within 5 minutes it’s idling 1300+

 

2 hours ago, Tractorman said:

Normally, I would not think the injectors could be an issue,

 

I only mentioned it because you know absolutely nothing about the history of  the injectors and the truck was behaving this way when you bought it.  I really don't think it is the injectors, but in your case I wouldn't rule them out.

 

Interesting regarding the your observations when revving the engine.  I will be interested in hearing the results of your test.

 

- John

[Mopar1973Man]

Two things 

 

1. Bad APPS idle validation switch.

2. Worn out injectors. Replace if over 100k miles.

 

As injectors wear out you will see engine load drop to zero and then the ECM can't cut fuel any deeper and idle starts to increase as they wear. For every 10 bar lost is roughly 1 degrees advanced in timing. Like my oem injectors idled at 850 RPM and popped to 260 bar which is a long ways below 293 bar which is lower limit.

Edited October 29 by Mopar1973Man