Attention: TDR Forum Junkies 
The root of this issue is that I get a very sporadic 10 Chimes and WTS light.
The truck has no codes set using my code scanner, or 3 on / 2-off ignition method.
By sporadic I am talking once or twice a year. This has happened after long hill decents but also while pulling ~ 6 - 10% grades under full load, towing ~10,000#’s with RPM’s at 2300 or so. It does seem to happen more when towing but the truck logs the most miles on towing trips so this may be coincidence.
It has happened when truck was empty as well but always during highway travel and at a steady rpm, not under hard acceleration.
I have never noticed any performance issues what-so-ever. Never a miss, no loss of power (except when it derates after the 10 Chimes), no excess smoke, no loss of mileage etc. The truck runs perfect as best I can tell.
I have read-up on the excess return flow issue and was planning to pay a shop to do the return flow test.
Before I did that I was thinking through what could cause the 10 chime “code”. It is my understanding that the ECM looks at rail pressure and uses the pressure transmitter to calculate flow rate.
Soo, I hooked up my code scanner as this also will display live PID data including rail pressure in KPA.
I have observed the following: The pressure reading is typically steady, it steadily increases as RPM increases and falls as RPM falls with some lag.
Here is what I am calling odd and am seeking feedback – At highway rpms for an extended amount of time ( 10 minutes or more) the Fuel Pressure will be steady in the 55000 KPA range, then at random times the fuel pressure reading displayed on the scanner will drop to something in the hundreds, say 700’s, it may bounce around that range for 3 -5 seconds then return to the 55000 range and stay there steady, a random time later this repeats.
This occurs randomly at different steady RPM’s ( cruise control set) and may happen every minute, or maybe every 10 minutes, its seems completely random. (Again no performance issues are ever noticed, even when towing in mountainous terrain)
The reading never seems to hang in the deviation low range for more than a few seconds
My current thought is that whatever is causing this low pressure reading may be triggering the 10 chime code if it happens to hang at the low range for too long.
I have removed, inspected, cleaned, added dielectric grease and reinstalled the Rail Pressure Sensor electrical connector. ( It looked very clean and rubber “boot” on connector appeared to already have dielectric grease on it – so nothing suspicious)
I closely inspected the connectors to the ECM for signs of rubbing, damage, oil intrusion etc. Nothing found. Disconnected batteries and removed ECM connectors, inside was immaculate clean, female sockets bright shiny brass. Cleaned with contact cleaner, dieltric grease around outside of plug and reinstalled.
Same observations remain.
I am suspicious of the Rail Pressure Sensor as I find it hard to believe that the actual pressure could be dropping this low without any sign of performance issues especially when pulling a grade. However, this would seem to me to be a very odd mode of failure for the sensor.
Has anyone seen these symptoms or have any comments ( if you were kind enough to read my whole post).
I have no problem replacing the Rail Pressure sensor but would like to try and verify beyond my knowledge or be able to test it before throwing a couple hundred bucks at it. Being it is so random it may be impossible to reproduce on any type of bench test???
Thanks - Jeff
The truck has no codes set using my code scanner, or 3 on / 2-off ignition method.
By sporadic I am talking once or twice a year. This has happened after long hill decents but also while pulling ~ 6 - 10% grades under full load, towing ~10,000#’s with RPM’s at 2300 or so. It does seem to happen more when towing but the truck logs the most miles on towing trips so this may be coincidence.
It has happened when truck was empty as well but always during highway travel and at a steady rpm, not under hard acceleration.
I have never noticed any performance issues what-so-ever. Never a miss, no loss of power (except when it derates after the 10 Chimes), no excess smoke, no loss of mileage etc. The truck runs perfect as best I can tell.
I have read-up on the excess return flow issue and was planning to pay a shop to do the return flow test.
Before I did that I was thinking through what could cause the 10 chime “code”. It is my understanding that the ECM looks at rail pressure and uses the pressure transmitter to calculate flow rate.
Soo, I hooked up my code scanner as this also will display live PID data including rail pressure in KPA.
I have observed the following: The pressure reading is typically steady, it steadily increases as RPM increases and falls as RPM falls with some lag.
Here is what I am calling odd and am seeking feedback – At highway rpms for an extended amount of time ( 10 minutes or more) the Fuel Pressure will be steady in the 55000 KPA range, then at random times the fuel pressure reading displayed on the scanner will drop to something in the hundreds, say 700’s, it may bounce around that range for 3 -5 seconds then return to the 55000 range and stay there steady, a random time later this repeats.
This occurs randomly at different steady RPM’s ( cruise control set) and may happen every minute, or maybe every 10 minutes, its seems completely random. (Again no performance issues are ever noticed, even when towing in mountainous terrain)
The reading never seems to hang in the deviation low range for more than a few seconds
My current thought is that whatever is causing this low pressure reading may be triggering the 10 chime code if it happens to hang at the low range for too long.
I have removed, inspected, cleaned, added dielectric grease and reinstalled the Rail Pressure Sensor electrical connector. ( It looked very clean and rubber “boot” on connector appeared to already have dielectric grease on it – so nothing suspicious)
I closely inspected the connectors to the ECM for signs of rubbing, damage, oil intrusion etc. Nothing found. Disconnected batteries and removed ECM connectors, inside was immaculate clean, female sockets bright shiny brass. Cleaned with contact cleaner, dieltric grease around outside of plug and reinstalled.
Same observations remain.
I am suspicious of the Rail Pressure Sensor as I find it hard to believe that the actual pressure could be dropping this low without any sign of performance issues especially when pulling a grade. However, this would seem to me to be a very odd mode of failure for the sensor.
Has anyone seen these symptoms or have any comments ( if you were kind enough to read my whole post).
I have no problem replacing the Rail Pressure sensor but would like to try and verify beyond my knowledge or be able to test it before throwing a couple hundred bucks at it. Being it is so random it may be impossible to reproduce on any type of bench test???
Thanks - Jeff
