P0192 and air in fuel head HELP

ericg88 · **Joined:** Wed Apr 03, 2019 8:34 pm **Posts:** 16

6148BC is the only number I see on this, but I'm going to go against my better judgement and trust the technician from Carter.

WWDiesel, I forgot to tell you I got your secondary filter get in the mail yesterday!

I'm gonna install this too, so I can monitor pressure just in case this pump isn't the right one.

ericg88 · **Joined:** Wed Apr 03, 2019 8:34 pm **Posts:** 16

Update: Good News: Lift pump is now installed and working properly. Primer pump is rock hard and no diesel leaks.

Bad News: Still exhibiting same symptoms and throwing a code. I'll check code when I get home.

After further experimenting, it really seems like limp mode triggers when I come to an abrupt stop/significant slow down after driving at highway speeds. It makes me think that something is shifting around as I break and causing a short or bad contact somewhere.

I'll clear codes and unplug the Fuel Pressure Sensor to see if I get another code, as suggested by Flash.

After that I guess it's time for a thorough investigation of the wiring harness. I guess I'll have something to do if we get quarantined

.

WWDiesel · **Posted:** Wed Mar 18, 2020 3:31 pm

ericg88 wrote:

Update: Good News: Lift pump is now installed and working properly. Primer pump is rock hard and no diesel leaks.
Bad News: Still exhibiting same symptoms and throwing a code. I'll check code when I get home.
After further experimenting, it really seems like limp mode triggers when I come to an abrupt stop/significant slow down after driving at highway speeds. It makes me think that something is shifting around as I break and causing a short or bad contact somewhere.
I'll clear codes and unplug the Fuel Pressure Sensor to see if I get another code, as suggested by Flash.
After that I guess it's time for a thorough investigation of the wiring harness. I guess I'll have something to do if we get quarantined

.

Based on your report, I would say most likely it is not fuel starvation issue since fuel consumption goes to minimum (idle) when you let off the go pedal when coming to a stop. Problem seems to point to an electrical or sensor issue.
The codes should be telling you what is triggering the limp mode.
Reminder, there are active codes, ones that turn on the DTC light on the dash, and then there are stored or pending codes some of which may not trigger a DTC light but are captured in memory. Both types of codes need to be read. Not all scanners can read both active and pending codes.
To truly diagnose your issue, you are going to have to monitor the voltage reading coming from the fuel rail pressure sensor during an event and see what the signal is telling the ECM.

This is a good condensed read on the subject:

https://www.nyvip.org/PublicSite/OBDII/diagnostic-trouble-codes.html wrote:

OBD II DTCs consist of a five-digit alphanumeric code. The DTC format and general code types are shown in this chart.

OBD II emissions related DTCs are from the powertrain and begin with P0xxx. P1xxx codes refer to manufacturer specific codes which often cover areas that are not emissions related and may not cause the check engine light to illuminate.

For P0xxx codes, the third character in the code identifies the system where the fault occurred. Numbers 1 and 2 are for fuel or air metering problems, 3 is for ignition problems or engine misfire, 4 is for auxiliary emission controls, 5 relates to idle speed control problems, 6 is for computer or output circuit faults, and 7 and 8 relate to transmission problems. Failures occurring in non-powertrain systems such as ABS, HVAC (Bxxxx, Cxxxx, Uxxxx codes) may be retrieved through the OBDII diagnostic link connector but do not illuminate the check engine light and are not involved with (NYVIP2) emissions inspections.

If the PCM commands the check engine light to illuminate there will be at least one P0xxx code stored in memory. However, in some cases you can have a situation where there is a P0xxx code in memory and the check engine light is not commanded to be illuminated. These codes are referred to as pending or maturing codes. Pending codes are caused by intermittent faults or faults that the PCM needs to see happen in two consecutive warm-up cycles to set the code. If the fault does not reappear within 40 warm-up cycles, the code will be cleared from memory. If the fault reappears for the specified number of times, the code will then mature into a diagnostic trouble code (DTC) and the PCM will command the check engine light to illuminate.

When a pending code is stored in the PCMs memory, freeze frame data is also captured. The freeze frame data will give the repair professional the actual operating conditions that were occurring when the fault triggered. This data allows for duplication of conditions so you can hopefully isolate the fault. The pending code feature is also helpful in trying to figure out why a particular system monitor will not set. The component or process that is the subject of the pending code is often involved as part of the enabling criteria to successfully complete a monitor.

WWDiesel · **Posted:** Wed Mar 18, 2020 4:55 pm

More on the P0192 problem checks:

---General Check – Check wiring harnesses very closely for any obvious signs of damage, such as from chafing, poor routing, or other subtle signs of damage. Check connectors closely for any bent or broken pins or corrosion. Make sure all connectors seat properly. Repair as necessary.
---Circuit Check – Disconnect the ECM and FPS. If no circuit problems are found, suspect a faulty sensor, but test (if possible) before replacing it.
---Check each line circuit (wire) for continuity from end to end. ECM connector to FPS connector. Resistance should be less than 1 Ω end to end.
---Check each line circuit for a short to each other and from each circuit leg to ground wire.
There are three wires going to FP sensor.
1. Grd -- is earth ground to chassis from the ECM. (Note: this ground circuit could be shared by some other engine sensors)
2, RPS -- signal wire that supplies variable voltage signal to ECM as fuel pressure varies.
3. Vref -- 5v power supply, should be constant and steady
---Sensor Check – All connectors firmly seated and KOEO (key on engine off), backprobe the FPS or ECM connections for the correct voltage & ground specifications. There should be a 5 V reference voltage (Vref), and ECM ground, and RPS signal. If all wiring circuit checks and checks pass, suspect a sensor fault, do not condemn the ECM until you have the system checked by a professional who should use a scope to monitor the voltage & ground at the FPS and the signal supplied to the ECM.

If Vref, RPS, and Ground all read 4.5 – 5.5 V, suspect an open ground circuit. If you’ve ruled out the circuit itself, it may be internal. Repair wire harness or replace sensor.
If Vref is 4.5 – 5.5 V and Ground is 0 V, RPS should read between 0.5 V and 4.5 V. If otherwise, replace the sensor.
You may be able to measure resistance directly on pressure sensor. Disconnect the sensor and measure across the terminals, not sure what the Ω should be from terminal to terminal, could not find it in the FSM. :banghead:

Gordon may know?

ericg88 · **Joined:** Wed Apr 03, 2019 8:34 pm **Posts:** 16

WWDiesel wrote:

More on the P0192 problem checks:

---General Check – Check wiring harnesses very closely for any obvious signs of damage, such as from chafing, poor routing, or other subtle signs of damage. Check connectors closely for any bent or broken pins or corrosion. Make sure all connectors seat properly. Repair as necessary.
---Circuit Check – Disconnect the ECM and FPS. If no circuit problems are found, suspect a faulty sensor, but test (if possible) before replacing it.
---Check each line circuit (wire) for continuity from end to end. ECM connector to FPS connector. Resistance should be less than 1 Ω end to end.
---Check each line circuit for a short to each other and from each circuit leg to ground wire.
There are three wires going to FP sensor.
1. Grd -- is earth ground to chassis from the ECM. (Note: this ground circuit could be shared by some other engine sensors)
2, RPS -- signal wire that supplies variable voltage signal to ECM as fuel pressure varies.
3. Vref -- 5v power supply, should be constant and steady
---Sensor Check – All connectors firmly seated and KOEO (key on engine off), backprobe the FPS or ECM connections for the correct voltage & ground specifications. There should be a 5 V reference voltage (Vref), and ECM ground, and RPS signal. If all wiring circuit checks and checks pass, suspect a sensor fault, do not condemn the ECM until you have the system checked by a professional who should use a scope to monitor the voltage & ground at the FPS and the signal supplied to the ECM.

If Vref, RPS, and Ground all read 4.5 – 5.5 V, suspect an open ground circuit. If you’ve ruled out the circuit itself, it may be internal. Repair wire harness or replace sensor.
If Vref is 4.5 – 5.5 V and Ground is 0 V, RPS should read between 0.5 V and 4.5 V. If otherwise, replace the sensor.
You may be able to measure resistance directly on pressure sensor. Disconnect the sensor and measure across the terminals, not sure what the Ω should be from terminal to terminal, could not find it in the FSM. :banghead:

Gordon may know?

Thank you so much for this. I've been dreading this and had no idea where to start. I've got some unexpected business to take care of this weekend but I should be able to start checking things on Sunday. I'll let you know what I find and try to document the problem once I've found it so others can use the info.

ericg88 · **Joined:** Wed Apr 03, 2019 8:34 pm **Posts:** 16

Update: I know this thread has been dead for a long time. I got really busy with work and life, I set the Jeep aside for a while.

I recently started driving it again and after a few days.... it stopped tripping into limp mode. It hasn't given me any issues for almost a month now. I imagine there's a bad wire somewhere that has adjusted or corroded itself into a better contact. I know I should keep prodding at it but I think I'm just gonna let it ride for now.

Now for a NEW problem! My ABS light is tripped and my odometer is no longer tracking miles. Speedometer still works. I did some road testing and it seems like the rear wheels are locking up when I brake hard, and I've read that the rear ABS sensor and wiring are known to go bad on the 2005 models. The wiring doesn't look bad at all and the contacts seem clean.

I'll test voltage and remove the imspect the sensor when I get back from my elk hunt.

ericg88 · **Joined:** Wed Apr 03, 2019 8:34 pm **Posts:** 16

Long overdue Update: SOLVED.

The problem was the Fuel Rail Pressure Sensor. The part cost 160 bucks from ID parts and took minutes to install. Been driving it for a month now and the issue is completely resolved.

P0192 and air in fuel head HELP

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