Engine only revs 0 to 1400 RPM and “no bus” issue

[Jimijack]

I bought this 2001 dodge ram 2500 quad cab 4 x 4 with a 5.9L Cummins diesel for $500 and I have already put thousands of dollars into it, so I’m glad I didn’t pay more. I received the truck as is, and it would start and idle, but when you push the gas it only has one speed, which is 1400 RPM no matter how much pedal you give it and my odometer is displaying a “no bus”error, however all of my gauges do work. The truck had an adrenaline tuner on it, which I verified with the company that it was bad, so I pulled it all off. I have a compound turbo set up, and they spin and the impellers appear tight and no leaks in the boots. I have 120 hp injectors installed and studded heads, along with a 4 inch exhaust, which were all installed by a previous owner. (unfortunately I have no access to the previous owner because my nephew purchased this truck and I got it off of him. Apparently the VP 44 was replaced just before I got it and the previous owner gave up on it). The first thing I did was put a new lift pump (Air Dog 100) on it and right now I have between 15 psi and 20 psi after the water/ fuel separator, so pressure is great. I sent my PCM and my ECM out to be tested and refurbished, however when I got them back and installed nothing changed. I also got a refurbished dash cluster, that is correct for my truck and guaranteed, but nothing changed. I cleaned every ground on the truck, and nothing stood out with those and nothing changed. I replaced the body control module and replaced the VP 44 injection pump a second time, and when that was done, nothing changed. I changed the cam position sensor and MAP sensor, and nothing changed. I checked all wiring harnesses and repaired any suspect wiring. I changed my a APPS sensor with one already mounted on a bracket and I have 4.70 V going to it. (I should know if that the only way to start the truck is to push the gas pedal to the floor, otherwise it will not start, but it will idle great all day long with a very slight surge) I unplugged every single sensor in order to see if it would make a difference with the “no bus” issue, but nothing changed.  Also I should note that every sensor connector, PCM, and ECU, have been cleaned and dielectric grease put into the connectors. There are no codes that I can get to display on the odometer with the key on and off three times, and the batteries are constantly being connected and disconnected since there is a drain on the batteries, so I don’t think, even if I had a code reader, that I could get any codes from it…I’m at my wits end with this thing. 

 

I know I threw a lot of parts at it, but it was all a learning experience and now I’m beginning to know the joy of owning a 24 valve dodge Cummins diesel truck, like the back of my hand… any help or advice would be much appreciated, thank you!

[Great work!]

Are you getting a wait to start light blink when you turn the key on. That means the ECM booted up and is alive.

[Jimijack]

Yes my wait to start light comes on and goes off as it should when the key is turned to the “on” position.

Every discussion thread that I’ve read concerning a “no bus” error deals with the instrument cluster gauges not working, however my gauges all appear to be working as they should and don’t go off or act erratic.  Of course, I do have a “check engine” light on, along with a “brake” light and an “airbag” light.  I changed the master cylinder and I have not bled the brakes yet, so that might be the “brake” light issue.  

Edited March 27, 2022 by Jimijack

[Mopar1973Man]

PSG on the VP44 is shot. That's called limited pedal and typically the VP44 is at fault. It has to do with the communication between the VP44 and the ECM. You can verify the TPS signal with the key on and engine off and watch the TPS value from 0% to 100% this means the ECM is saying the right thing but I'm pretty sure the VP44 PSG is bad. I've had this once before new VP44 and installed it and did the same thing. After swapping back out with a another VP44 the problem was gone. Might check error codes and a P1689 might be present too.

 

Oh yeah Dead pedal is only when it just idles (800 RPM) and does nothing. Limited pedal might very to different RPM levels and stop. Typically limited pedal snaps directly to that limit regardless of how light you press the pedal. 

 

No Bus is going to be the CCD Network. You can measure the bus voltage from the OBDII port on both the CCD + and CCD - vs ground (body). This should be 2.49V and 2.51V after the modules come to rest and quit talking. The cluster is what sets the bias voltage. 

 

Edited March 27, 2022 by Mopar1973Man

[wil440]

You say you have a check engine light on on the dash ?? If so you will have fault codes, connect a good scanner, I bit the bullet a few years ago and bought a Snap On Modis but  there is cheaper that work fine, I've always found the key deal to be no use at all also with a scanner you will be able to see live data.

I've only ever had 2 codes on my truck in 5 years touch wood, one was APPS and the other was MAP sensor, always scanner first buy parts second

[Mopar1973Man]

25 minutes ago, wil440 said:

You say you have a check engine light on on the dash ?? If so you will have fault codes, connect a good scanner, I bit the bullet a few years ago and bought a Snap On Modis but  there is cheaper that work fine, I've always found the key deal to be no use at all also with a scanner you will be able to see live data.

I've only ever had 2 codes on my truck in 5 years touch wood, one was APPS and the other was MAP sensor, always scanner first buy parts second

 

Absolutely true. Best to start your diagnostics with good tools and not use the key trick or cheap code readers. Live data is very handy for diagnostics even if you had a Quadzilla tuner that would open the door a bit even for diagnostic info displayed from the ECM. Like TPS values, and engine load values, etc. Yup best to do your diagnostics first like read the error codes and then look them up on the website and do the diagnostic steps for resolving the issue. Some times it can be just wiring issues but that why the diagnostics to to make sure what is damaged and getting the right part.

 

OBDII ERROR CODE LIST

[Jimijack]

I appreciate the very detailed responses from you guys.  It’s definitely hard to believe (but I will have to swallow) that I received a refurbished Thoroughbred Diesel VP-44 with a bad PSG.  I actually paid $225 more for this VP-44 because they said it would be a brand new PSG, instead of an existing PSG that is only tested for function.  I will go through the testing procedure that you gave me to verify.  I actually found today that I have a 920, 921, and 999 error codes from the key on check, which I think are just the standards for a bad PCM or “no bus”connection?

[Mopar1973Man]

18 minutes ago, Jimijack said:

I received a refurbished Thoroughbred Diesel VP-44 with a bad PSG.  I actually paid $225 more for this VP-44 because they said it would be a brand new PSG, instead of an existing PSG that is only tested for function.

 

Sorry... The truth is that typically a TRUE rebuilt VP44 that is Bosch Certified REQUIRES a NEW PSG on every unit. Then the VP44 is placed on a Bosch 815 test stand for 3 HOURS. During the 3 hours it does all the tests and then after all tests have pasted then the PSG is flashed with the software. This why I will not buy any VP44 that is budget like that because there is ZERO way to verify the health of the PSG or the VP44 because it was never on the test stand. This prompted us to produce a page for certified Bosch Rebuilders. Just think its 3 hours for testing so most people don't re-certify a pump because using the test stand for a used pump takes to long to be tested so typically they are sold for cheap price. 

 

 

I'm also building a vendor page so others can list vendors they dealt with and then review them as well.

https://mopar1973man.com/vendor.htm/vendor/

 

Edited March 27, 2022 by Mopar1973Man

[Jimijack]

I really appreciate the help, so thanks again 🙏🏻

[wil440]

13 hours ago, Mopar1973Man said:

best to do your diagnostics first like read the error codes and then look them up on the website and do the diagnostic steps for resolving the issue.

True but I'll add a little

I've seen instances of the Cat dealer here field service engineers  ( which I was )  turn up to a machine with Cat ET  (which is "electronic technician " diagnostics plugin) and Cat SIS (supplementary information system) SIS is basically parts manual, workshop manual, service manual, diagnostics manual all rolled into one, laptop based for every machine Cat has ever built 

Connect ET and get codes then don't follow the listed steps for diagnosis, yes certain faults by all means pick the cheap easy first like cutting out change fuel filters first

Follow the diagnostic steps and if in any doubt do it again to test