Cummins 5.9 dead pedal

[ewo1]

Ok so I am officially stumped with this problem, DEAD PEDAL.

I got my hands on a 1998 Thomas bus with a 24v 5.9 cummins., vp44 pump.

Motor starts up right after the post test, will not start, only crank, if you try to start before the post test is completed.
That being said, once it starts it does one of two things, runs at a nice smooth idle lasting for a couple of minutes OR starts up and idles but then shuts down after 5-10 seconds. It does either one at random.

So far I replace the fuel filter, lift pump, crank and cam sensor.
Before replacing both sensors it would only idle for about 5 seconds and shut off.

When it does do the smooth idle, I can depress the gas pedal and nothing happens, in fact motor shuts down.

Has anyone experienced this before?

Also, can I manually pull codes on a Cummins like can be done on a DT motor?

If yes, can someone please point me in the direction on how to do this.

Thanks..

[ewo1]

Well I found some good info on 5.9 problems and a good writeup on steps/procedures to try.

For anybody interested...especially other 5.9 owners...
Found it here -> https://www.bluechipdiesel.com/troub...uick-reference

This is what I found out so far... (from the bluechip website)

Dead Pedal

This is THE MOST COMMON DRIVABILITY COMPLAINT and is an intermittent one that happens most often when the truck is hot or working harder, but can occur when cold too. My experience tells me that 4 times out of 5, Dead Pedal is worse hot, but 1 time in 5 it is worse cold! The symptom of Dead Pedal is rarely caused by the APPS (Accelerator Pedal Position aka Throttle Position Sensor) and 90% of the time it is caused by a faulty computer on the top of VP44 Injection Pump. These numbers are NOT an exaggeration. Computer failures are due to the “Lead Free” solder connections on the circuit board in the computer becoming crystalline over time, which causes an intermittent electrical connection and intermittent Dead Pedal symptoms. Its use is mandated by the Federal Government!

There are no codes that specifically diagnose Dead Pedal or that will condemn the computer and therefore the VP44. This is an instance where a lack of codes is most important, and where you have to prove that the only other component that could cause this symptom, the APPS, IS or IS NOT the cause of Dead Pedal.

The lazy inaccurate way to diagnose the APPS or TPS as the cause of this drivability issue is to scan or read the ECM (not the PCM) to check for any codes pertaining to the APPS, such as a 121 or 122. Codes 121 and 122 only indicate that the voltage going in or coming out of the sensor was outside of the desired parameters, at least once, since the codes were last cleared. Therefore these codes do NOT tell you what happens to the signal when they ARE within appropriate parameters, which is what really matters. If you DO have either or both of these codes you MAY OR MAY NOT need an APPS. To diagnose the APPS accurately you need to use an oscilloscope or an ANALOG voltmeter, one with a needle, to measure and monitor the signal voltage on the blue wire with a black tracer, on a Dodge, in the APPS electrical harness plug. A scan tool or a digital voltmeter has too much averaging or buffering of the signal to be useful for this test. First verify the appropriate voltage range and voltage apply rate with the engine off. Turn the ignition key to the “on” position and slowly press on the throttle and slowly release it. You should see voltages from about .6 volt to 3.5 volts, and not ever see a jump in voltage, or the needle bounce. It should go up and down smoothly, directly related to throttle movement. If it repeatedly or intermittently jumps up or down, then replace the APPS. The adjustment of low voltage at idle, or “resetting” or “recalibrating” the APPS is NOT as important as some people want you to think, and does NOT cause Dead Pedal. The ECM learns the range when you do the install of the APPS correctly and does NOT cause any drivability issue in my experience.

As this sensor can be very intermittent, I strongly suggest you ALSO do the same test when driving the truck to prove the APPS is or isn’t the cause of your Dead Pedal OR DRIVABILITY issue. Extend the signal wire used in the previous test up to the dash of the truck, hooked to the analog voltmeter, and drive it until Dead Pedal or naughty thing happens and look at the voltage on your voltmeter. If you are holding the pedal still and the voltage drops when the engine drops power, or the needle quivers at the same frequency as the stutter, skip, or miss, you need an APPS. If the voltage stays the same and the power drops, you need an Injection Pump!

[PorchDog]

VP44's do fail. However-- I suspect the reman units will have better solder joints-- because the folks that rebuild them would not use lead free solder.

GM had some injector pump computers fail in the 90's because of the lead free solder-- I don't want lead on house hold plumbing-- but it sure works dang good in a lot of other places...

I have a 1999 Dodge pickup where the pump failed at less than 80,000 miles, and was replaced by the previous owner many years ago. Still works fine. One tip when looking for these trucks used was that if the original pump had been replaced-- it was actually a good thing.


So-- if you do have to replace the pump-- it will actually be an upgrade, and plus---you are not broken down in timbuktu....

[fo4imtippin]

If you do have to replace the pump, might be a good time for a P-Pump conversion if your transmission isn't electronic. You might even be able to sell your ECU and old pump (as a core or repair) to cover the difference.

[ewo1]

So I am back on this project on trying to figure out what the heck is going on with this engine.

So far I have replaced the crank and cam sensor, lift pump, fuel filter and also replaced the VP44 pump (rebuilt).

Before it would start, run for about 5 seconds and then shut off by itself.
Dead pedal also was present.

After all the parts swapping, it now starts and idles fine, forever but...still got dead pedal!

I reached out to a Thomas bus dealer and they supplied me with wiring diagrams but they do not have a diagram for the ECM side of the harness. I want to know the pinouts so I can test the harness from the gas pedal to the ECM.

Throttle pedal, I do have a good ground and 5 volts coming from the ECM to the pedal.
I also test the idle control function of the throttle pedal. This is nothing but a single pole double throw switch inside the pedal. This is the section of the harness I want to test for continuity. This is why I need the pinout for the ECM.

So if anyone can share with me a pinout of the harness I would greatly appreciate it!

I have attached the wiring diagram for the pedal side. If anyone has any tips...I could surely use some right now! The circuit is called "Throttle Pedal Assembly"

I don't have a code reader that works, need a laptop so I can't talk about codes but I am working on getting a laptop!

LOL...After I wrote this I went back to look at the diagram and noticed that the drawing already identifies the ECM pin number for the wires....
That problem is now solved...but I need ideas on how to get this fixed !

Anyone know how to manually pull codes on a '98 Thomas MVP with a 5.9. ISB?

[PorchDog]

After looking at the wiring diagram---

I would sure be suspicious of the idle switch. Looks like a ground direct to battery or somewhere-- and then the two leads going back to the ECM-- my guess would be that those two leads tested as close to the ECM as possible should toggle between maybe five volts and ground as the pedal is slightly depressed.

My assumption is that if that idle switch is not operating correctly-- it would disable the variable potentiometer that controls engine speed.

[ewo1]

Originally Posted by PorchDog

After looking at the wiring diagram---

I would sure be suspicious of the idle switch. Looks like a ground direct to battery or somewhere-- and then the two leads going back to the ECM-- my guess would be that those two leads tested as close to the ECM as possible should toggle between maybe five volts and ground as the pedal is slightly depressed.

My assumption is that if that idle switch is not operating correctly-- it would disable the variable potentiometer that controls engine speed.

Thanks for taking a look at this, it’s not easy doing this by yourself. It really helps me when I can talk it out in order to better understand.

I had read a post on another Rv forum and yes there was on guy who found a loose wire on the fast idle switch that was causing a dead pedal situation.

I was gonna test for continuity on the pedal switch itself, the SPDT switch. If you take notice, one side is normally open and the other side is normally closed.

My thinking is that when you press down on the pedal, that switch goes from normally closed to open, sending a ground signal to the ECM via idle validation #1 and telling it, it’s ok to turn up the rpm’s!

So I was gonna check those wires for continuity and also the ground wire too.

Since you mentioned it, and it was in the back of my mind, I am also gonna test for continuity on that fast idle switch too.

God I hope it’s as easy as this…..

[ewo1]

So I did a quick test, I ran a new temporary ground wire from the pedal, the center tap of the DPST switch that is built into the pedal, position A on the connector, to the bus chassis and still have no change - DEAD PEDAL !

I found on another site a "testing" procedure for dead pedal.

I'm posting it up for two reasons, one to share and the other is so I can find it quickly if the info was needed again.

what really sucks is that I just put in a rebuilt pump, has zero miles on it and everything is again pointing to a bad pump.

Here it is: (SOURCE)


Dead Pedal

This is THE MOST COMMON DRIVABILITY COMPLAINT and is an intermittent one that happens most often when the truck is hot or working harder, but can occur when cold too. My experience tells me that 4 times out of 5, Dead Pedal is worse hot, but 1 time in 5 it is worse cold! The symptom of Dead Pedal is rarely caused by the APPS (Accelerator Pedal Position aka Throttle Position Sensor) and 90% of the time it is caused by a faulty computer on the top of VP44 Injection Pump. These numbers are NOT an exaggeration. Computer failures are due to the “Lead Free” solder connections on the circuit board in the computer becoming crystalline over time, which causes an intermittent electrical connection and intermittent Dead Pedal symptoms. Its use is mandated by the Federal Government!

There are no codes that specifically diagnose Dead Pedal or that will condemn the computer and therefore the VP44. This is an instance where a lack of codes is most important, and where you have to prove that the only other component that could cause this symptom, the APPS, IS or IS NOT the cause of Dead Pedal.

The lazy inaccurate way to diagnose the APPS or TPS as the cause of this drivability issue is to scan or read the ECM (not the PCM) to check for any codes pertaining to the APPS, such as a 121 or 122. Codes 121 and 122 only indicate that the voltage going in or coming out of the sensor was outside of the desired parameters, at least once, since the codes were last cleared. Therefore these codes do NOT tell you what happens to the signal when they ARE within appropriate parameters, which is what really matters. If you DO have either or both of these codes you MAY OR MAY NOT need an APPS. To diagnose the APPS accurately you need to use an oscilloscope or an ANALOG voltmeter, one with a needle, to measure and monitor the signal voltage on the blue wire with a black tracer, on a Dodge, in the APPS electrical harness plug.

A scan tool or a digital voltmeter has too much averaging or buffering of the signal to be useful for this test. First verify the appropriate voltage range and voltage apply rate with the engine off. Turn the ignition key to the “on” position and slowly press on the throttle and slowly release it. You should see voltages from about .6 volt to 3.5 volts, and not ever see a jump in voltage, or the needle bounce. It should go up and down smoothly, directly related to throttle movement.

If it repeatedly or intermittently jumps up or down, then replace the APPS. The adjustment of low voltage at idle, or “resetting” or “recalibrating” the APPS is NOT as important as some people want you to think, and does NOT cause Dead Pedal. The ECM learns the range when you do the install of the APPS correctly and does NOT cause any drivability issue in my experience.

As this sensor can be very intermittent, I strongly suggest you ALSO do the same test when driving the truck to prove the APPS is or isn’t the cause of your Dead Pedal OR DRIVABILITY issue. Extend the signal wire used in the previous test up to the dash of the truck, hooked to the analog voltmeter, and drive it until Dead Pedal or naughty thing happens and look at the voltage on your voltmeter. If you are holding the pedal still and the voltage drops when the engine drops power, or the needle quivers at the same frequency as the stutter, skip, or miss, you need an APPS. If the voltage stays the same and the power drops, you need an Injection Pump!

[ewo1]

Here is a really good wiring diagram that I am using to help me understand how the VP44 is wired up.
It for a Dodge pickup, not a bus, but the architecture I feel is the same.

I am starting to think and really hoping that it's just a bad ground or maybe questionable connections.

But where ???

[fo4imtippin]

This post confirms my gut feeling to carry a spare VP44 in my parts box.

[ewo1]

Originally Posted by fo4imtippin

This post confirms my gut feeling to carry a spare VP44 in my parts box.

You ain't kidding!

It's a lucky thing that I like challenges and this one is truly a challenge!

All the posts I read, it seems that the vp44 computer being culprit #1 for this problem.
But I have a fresh, newly rebuilt pump from a very reputable diesel shop here in Miami.
I have found dozens of threads on this issue and many of the fixes would surely surprise you. It seems like half of the fixes are really not fixes but just pure co-incidence on temporarily fixing the intermittent issues of dead pedal.

I am really surprised that no one dares to chime in on this really weird but seemingly common failure.

In the end, I'm gonna figure it out and share what I did to get it done!

[PorchDog]

I have a VP44 in a 1999 Dodge Pickup, which currently has 84000 miles on it. I bought it from the folks who purchased it new-- with around 80,000 miles on it-- and the original pump had already failed and had been replaced before I bought the truck from them.

From what reading I have done-- most of the time the replacement pumps were better than the original-- hopefully they were repaired with leaded solder, since the lead free solder appears to be the source of the problem.

This is another case of the government causing grief to the guys at the bottom of the food chain. This was "the beginning of the end" for reliable, low maintenance diesel engines. Our family has a 70's vintage Ford 555 Backhoe, a John Deere 4020, a 5900 Ford tractor, a 5610 Ford tractor, and a Massey Ferguson 231 Tractor-- and guess what-- they all start and run fine. They still serve the purpose for which they were designed. All the emissions diesels will be in the scrapyard...

I'm 64 years old-- and I have witnessed how the government has taken reliability and long life off the table through regulations that in the long term cause more harm than good.

[Booyah45828]

I hate to say it, but when dealing with electrical issues on an electronic engine, a scan tool to view live data and codes is almost as important as a dvom. There is a reason that the ecm isn't registering your pedal actuation. That could be a faulty pedal, shorted high idle switch, faulty cruise control switch, faulty brake pedal switch, or a faulty ecm itself.

Over the years I've learned that nothing on an isb is failure proof, I've replaced at least one of everything.

With it idling, is the check engine light on? I wouldn't trace wires or cut apart harnesses without knowing codes or at least a direction to look to. Use the correct probes when checking the connectors, they have issues with loose connector contacts caused by people jamming probes into them.

[ewo1]

Originally Posted by Booyah45828

I hate to say it, but when dealing with electrical issues on an electronic engine, a scan tool to view live data and codes is almost as important as a dvom. There is a reason that the ecm isn't registering your pedal actuation. That could be a faulty pedal, shorted high idle switch, faulty cruise control switch, faulty brake pedal switch, or a faulty ecm itself.

Over the years I've learned that nothing on an isb is failure proof, I've replaced at least one of everything.

With it idling, is the check engine light on? I wouldn't trace wires or cut apart harnesses without knowing codes or at least a direction to look to. Use the correct probes when checking the connectors, they have issues with loose connector contacts caused by people jamming probes into them.

Check engine light only comes on, then goes off, when the ECU is performing it's POST. With the engine idling, check engine light is off.

I like your ideas about shorted or faulty switches. I am going to unplug those two switches, remove them from the circuit if you will, and see if there is any change.

[Booyah45828]

Well sometimes you'll find, especially in cruise systems, that switches aren't an on/off value, but change the resistance/voltage value given to the computer. So unplugging the switch gives a value that's out of range, and will disable the whole system.

You can try it, as you're likely out nothing by it, but take the results with a grain of salt so to speak.

[ewo1]

So we are still trying to figure out what is wrong with this bus.

After replacing some parts, I finally found a guy to come buy and pull codes. We get one code, over and over again and the DTC code is 2559.

Insite says it suffers from lack of communication from the engine ecu to the TCU...oh wait, it got an AT545...so NO TCU !

I could really use some help with this.
Are options are:
Sending the ECU of to a shop for testing, cost is $100 or find another ECU to test with.
Can't find one from a bus...

Our ECU has no label on it to identify it so...would a regular ECU from a dodge ram 24v pickup truck work?

[fo4imtippin]

Originally Posted by ewo1

So we are still trying to figure out what is wrong with this bus.

After replacing some parts, I finally found a guy to come buy and pull codes. We get one code, over and over again and the DTC code is 2559.

Insite says it suffers from lack of communication from the engine ecu to the TCU...oh wait, it got an AT545...so NO TCU !

I could really use some help with this.
Are options are:
Sending the ECU of to a shop for testing, cost is $100 or find another ECU to test with.
Can't find one from a bus...

Our ECU has no label on it to identify it so...would a regular ECU from a dodge ram 24v pickup truck work?

I believe the dodge version only has one plug and maybe less Rom size or something. The number I have on mine is

3944104

There's one on eBay that will program it and send it back. You might be able to have them load a higher hp tune from an RV while your at it if you want to risk your 545.


I never got the story, but my ECU has been replaced about 35k ago by the school district. They look like they have a weak point and I plan to carry a spare if I leave CONUS.

[Booyah45828]

If you get a 2559 and have an at545 you typically have a calibration mismatch.

The ecm does occasionally fail, and I'll catch people swapping ecm's from truck-truck all the time. A Dodge ecm will not work on this. The ecm you need must be programmed to your exact vehicle. You can occasionally get lucky if the donor ecm options match the truck, but there are so many different options available I wouldn't try it.

Bluebird has the engine serial number on a data plate inside the bus. I don't know if thomas does or not. But you can take that, see if it matches the serial number on the engine's data plate, and then take your current ecm to a cummins shop and see if they'll flash the appropriate calibration to it. If your current ecm is junk, I recommend biting the bullet and getting a new one. We haven't had much luck with those ecm's from rebuilders.

[Memetocene]

I experienced the same issue with a dead pedal and it was the high idle rocker switch not returning control to the accelerator pedal. I have yet to replace the high idle switch but she drives and accelerates fabulously.

[Memetocene]

This was an excellent suggestion that solved my problem.