P0191 Code - 2012 Ram 2500

[RamVenture]

I’ve been fighting a check engine light for about a year for the following code P0191 (Fuel Rail Pressure Sensor Circuit Range) on my 2012 Ram 2500 stock configuration with about 145,000 miles. I think i've looked at most of the online threads on this code and no one seems to come back and post an update on how the issue was resolved other than fuel filter or fuel sensor replacement. I've replaced the fuel rail pressure sensor with bosch replacement, on my third fuel filter (Wix, Napa Gold and currently on Mopar 3 micron filter). Recently installed bosch fuel control actuator (FCA) sensor but hasn't fixed the issue. The truck seems to run well but would really like to get the issue fixed. After logging and reviewing data, it seems to trigger when the truck is at idle (stop light). Attached is some logged data, you will see the fuel pressure seems to oscillate at idle but can still make high pressure. For comparison I borrowed by neighbors 2010 Ram 2500 6.7 (data with black background) and his fuel pressure curve is smoother and more closely matches Command Pressure. Does anyone happen to have access to the service bulletin for this code to get an idea of what else to check or how to test the fuel pressure sensor? I doubt I got a bad sensor, but maybe it's possible. More recently I've noticed fuel residue by the fuel rail tube connection to injector tubes, see photos, most visible by #5 & #6. The first time I took a look was when the pressure senor was replaced and of course there was fuel due to replacement. As I'm looking at it now it looks to be fresher so I'm thinking this may be the issue or at least I have a small leak. Any thoughts guys? I guess I'm trying to avoid pulling all the injectors till last resort. I ordered oil sample kits to see if they detect fuel in the oil. If the oil sample comes back normal can the injectors still be bad? Thanks for your time and assistance!

View attachment 132881

 

[Signal73]

I can’t be too much help but your leak looks more like engine oil to me, more than likely the rocker cover gasket. Is there a relief valve on the rail as well? I maintain a 11 5500 and had the 191 code a few months back and replaced the sensor with a Bosch. I never cleared the code and it wasn’t there for a few weeks after the repair but it popped up about a week ago. I scanned the truck and it knew it was never cleared so I went ahead and cleared it and am monitoring it for a reoccurrence. Hopefully I don’t see it again!

 

[RamVenture]

Yes, still have stock relief valve (3rd owner, I haven’t changed it). I thought maybe it could be the leak source, but looking at the pressure I would expect more pressure drop at high pressure. I’m soon due for valve lash adjustment and could get the gasket replaced. I’ve thought of cleaning up the area to get better idea what’s leaking but didn’t want to get rid of the evidences for an experienced mechanic. I’ve cleared the code many times. It will stay logged at permanent. After clearing it comes back as pending then active.

 

[Timd32]

I did not get into the weeds with this but I saw a TSB that was pretty old 2013, about an update for that code and relates to the P0191 Circuit Performance.

NUMBER: 18-001-13
GROUP: Vehicle Performance
DATE: January 05, 2013

There is nothing to really share on that from my end I have no access to any sort of dealer level scans or flash info, but in general there could be something that helps with that at the dealer level.

Here is the basics I had available, still did not read it very quickly just sharing the info requested.

Good luck with your repair. Hope you get it sorted out.


DTC
P0191

Symptom Descriptor

Fuel Rail Pressure Sensor Circuit Performance

Probable Causes

• Fuel Rail Pressure Sensor (FRPS)
• 
  
• Injector Leakage

 

[RamVenture]

Timd32,
Thank you for the information. I missed the Powertrain info pdf you included, good information. I finally received the oil sampling kits from Blackstone. This weekend I went to pull a sample through the dipstick tube with 1/4" tubing and it's hitting something about 3in from reaching the oil. I can hear the pump sucking air...shoot. They will be sending 1/8" tubing, I hope it works. The bulletin has good information, but i'm hoping someone can help me make sure i'm understanding the information correctly. Following the flow chart at Step 2 is seems to imply my truck should have a fuel pressure reading above 870 psi. This would be when i turn the key to on but before i fire up the engine, is that correct? Based on my scanner I'm at 0 psi until i fire the engine. This would imply i probably have a leaky injector. Interesting thing is my neighbors 2010 6.7 reads the same at start us (no pressure till firing the engine). Can some confirm if they have rail pressure above 870 psi at key on? Thanks guys, learning a lot.

2.FUEL RAIL PRESSURE SENSOR
1. With the scan tool, monitor the actual fuel pressure reading while the ignition is on and engine is not running.
Is the actual fuel pressure reading above 870 psi?

Yes Go To 3

No Go To 4

4.CHECK THE INJECTOR RETURN FLOW
1. and perform the INJECTOR RETURN FLOW TEST. (Refer to 29 - Non-DTC Diagnostics/Drivability - Diesel - Diagnosis and Testing)

Does the injector drainage meet the test specification?

Yes Replace the Fuel Pressure Sensor in accordance with the service information.
Perform the POWERTRAIN VERIFICATION TEST - 6.7L. . (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure)

No Repair cause of high Fuel Injector leakage.
Perform the POWERTRAIN VERIFICATION TEST - 6.7L. . (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure

 

[sag2]

You should have no rail pressure unless the engine is cranking or running. You might see a hundred or two PSI with key on, but that is just because the sensor is not really calibrated to read that low. The pressure is actually zero.

 

[RamVenture]

I guess I’m little confused about 870psi threshold. What does “ignition is on and engine is not running” mean?

No pressure does make sense to me at key on. I’m thinking the lift pump does send some fuel to the inject pump but it’s got to be too low to register at the rail sensor. This also in keeping when i turn the engine off rail pressure goes to zero in about 2 seconds.

 

[Timd32]

I think they want to make sure it's below 870psi with the engine off. If it was above 870psi step 3 suspects there is an issue with the sensor. So zero is a good thing move to step 4, skip 3.

 

[RamVenture]

Thanks for calcifying things, I got it mixed up. Sounds like I need to have my injectors tested. Wish there was a way to test them without pulling them. Don't want to do this work at my local dealer, bad reviews overpriced parts. I really need to get my oil analysis done and if comes back positive for fuel then it's pretty obvious that's the issue. Any recommendations on things I should have done while they have the valve cover off? I'm thinking I should have the valve lash adjustment (i'm due in about 5k miles) and rocker cover gasket. My understanding when replacing injectors is to also replace the injector tube and fuel line. Any other items? Thanks again.

 

[RamVenture]

I got the oil analysis form Blackstone for the Ram and no fuel was detected in the oil. They said the oil looked good and could run it another 2k miles. If I had a leaky injector shouldn’t it show up in the oil? So either CP3 pump not performing up to spec or excess fuel return are my thoughts. Where else can you lose fuel pressure? Where does excess fuel get routed to, fuel filter, fuel tank? What’s the check/fix for excess fuel return? I don’t think it’s the CP3 pump as I’m not noticing any issues at speed. Thanks for the help.

 

[Ozymandias]

Did you do any updates to your trucks computer through the last ten years?
Is it up to date?
Because you can hunt ghosts for ever if they are built into and corrected later on sometimes years after production.

 

[RamVenture]

I bought the truck used and going on 2 years in June. Had if for about 5 months before started get this code. I haven't gotten any updated on the truck that i'm aware of. Not sure what the prior owners did. On a road trip in Texas, I got an EGR code and took it to a Ram dealer. They did EGR cleaning (didn't work, had to pay again to have it replaced). I hadn't seen the P0191 code on my scanner. Dealer told me about it and sure enough next day check engine light came on. Sometimes I wonder if they did something or maybe a lose wire. the code comes and goes. I did check with Ram corporate and based on my VIN all the recalls have been performed. Are you suggesting I take it to the dealer for an update?

My neighbor has 2010 2500 and bricked his ECM using an emissions compliant tuner while changing tunes (think it was a SuperChips tuner). Had the truck towed to the dealer and had his ECM reprogrammed. He said the dealer told him the updated program got him some extra power. Sounds to me they probably have updated software for the truck, but probably won't load it unless required to.

 

[Topzide]

Call dealer to see how much for update flash.Just because it shows recalls have been done, doesn't mean software has been updated! This may fix a lot on issues, some seen and others unseen. Staying up to date really help these trucks run their best!

 

[RamVenture]

I've been hesitant to post a follow-up, but here it goes. In March I pumped out some oil through the dip stick to have Blackstone test the oil and see if oil had high fuel content. Thinking maybe a leaky injector may be the source of my fuel pressure issue, no fuel was detected. One thing I hadn't mentioned in my prior post was the oil level on the dip stick was about 1/4" past full mark when checked in the morning before starting. I removed about a quart of oil and got the level down to the full mark. The P0191 code went away a few days later and hasn't come back since (knock on wood). Figured it was just a matter of days before it came back, but still hasn't trigger 2 months later. In a few days we leave for a month-long road trip so we'll see that happens. I have noticed it's hard to get a good read on oil level once the truck has been running unless it sit for a long time. I know only check it in the mornings before starting. I remember reading in the manual is said to check 5 mins after shutdown. The mechanic I've taken the truck to said this truck takes an extra quart of oil. I'm not so sure about that any more. Next oil change will only be 3gal and adding Femco drain valve. As I mentioned prior, I could clear the code and hit the road (1500 mi road trip) and the code wouldn't pop. Then a couple days of driving around town once we were back and it would pop up again. Sometimes I thought it was a lose wire as it often seemed to pop after crossing an intersection with valley gutter or bump at low speed. I've read some threads about over filling on oil and it takes a long time to properly drain all the old oil out. I haven't seen much with regards to the problems high oil causes. Maybe too much oil sloshing around at low speed? Hopefully someone more familiar how these diesel engines work can provide some insight if high oil level can affect fuel pressure. Thanks!

 

[Ozymandias]

Sorry to take that but oil level has nothing to do with rail pressure I our trucks.
The ECM has no clue how much oil is in the pan nor does it know the oil pressure.
There is no electrical, mechanical or hydraulic connection between these two.

But I've no clue why your 191 doesn't show up anymore, it could be ambient temperature - or the wiggling around on the wires solved a bad connection somewhere, it's al guessing.
But the oil level isn't the solution.

 

[RamVenture]

Went to pull the trailer out of storage today and code popped at a stoplight coming home. I have no idea, maybe lose wire. Didn’t think about temperature. Leaving AZ 100 degree temp for cool northern states.