2004 Liberty 3.7L high fuel rail pressure

[Intermechanico]

Good morning, good work.

The results of your testing suggest that the upstream O2 sensors are actually Out of Range Low (Less than .1 volt)

Do you happen to have the old O2 sensors to reinstall?

I’m trying to wrap my head around why the O2 sensor voltage is so low, with the PCM sitting at the pull up voltage if they’re new sensor, and all I can come up with is that they are defective or inappropriate for the application.

Normally, even defective O2 sensor(s) would allow the engine to run normally when cold (in open loop), but your long term adaptive fuel trim will affect the open loop fuel curve as well, and we know your Left Bank long term trim is sitting at -32%, which will lean out that bank and cause rough running when cold as well.

Don’t worry, we’ll get there. Ideally we can install the old O2 sensors, reset adaptive fuel trim and kind of restart this process.

 

[DadOSix]

Good morning, good work.

The results of your testing suggest that the upstream O2 sensors are actually Out of Range Low (Less than .1 volt)

Do you happen to have the old O2 sensors to reinstall?

I’m trying to wrap my head around why the O2 sensor voltage is so low, with the PCM sitting at the pull up voltage if they’re new sensor, and all I can come up with is that they are defective or inappropriate for the application.

Normally, even defective O2 sensor(s) would allow the engine to run normally when cold (in open loop), but your long term adaptive fuel trim will affect the open loop fuel curve as well, and we know your Left Bank long term trim is sitting at -32%, which will lean out that bank and cause rough running when cold as well.

Don’t worry, we’ll get there. Ideally we can install the old O2 sensors, reset adaptive fuel trim and kind of restart this process.

Not OP - but - do you think the values are skewed because the jeep is not seeing OEM / ngk sensors?

It has long been notesd here that aftermarket electrical parts drive the jeep computers crazy.

Ngk copper plugs are preferred over the newer tech stuff. From my 2 jeeps, i learned that the only substitute coils i could use were Standard Motor Product ones. Just my 2 cents.

Thanks for sharing your expertise! Learning more as i read your walk thru.

 

[04Liberty#!]

I really appreciate the feedback.

I have the old sensors and will reinstall and repeat the tests.
Might be tomorrow.
Regarding the coils, all I can say is they look just like the ones I replaced.

Is the 49psi Fuel Rail Pressure for this make and model correct?

 

[Intermechanico]

Not OP - but - do you think the values are skewed because the jeep is not seeing OEM / ngk sensors?

It has long been notesd here that aftermarket electrical parts drive the jeep computers crazy.

Ngk copper plugs are preferred over the newer tech stuff. From my 2 jeeps, i learned that the only substitute coils i could use were Standard Motor Product ones. Just my 2 cents.

Thanks for sharing your expertise! Learning more as i read your walk thru.

I read this as well, but I don’t want to break out the parts cannon just yet. The good news is the OP has the originals and can swap them back in to verify.

Apparently the issue with some aftermarket O2 sensors has to do with inadequate heater elements; that model requires ~600°c to begin generating voltage at the signal output

 

[04Liberty#!]

Update:
I was able to get stable Fuel Rail pressure between 52psi and 54psi with a salvaged FPR from and 2002 Liberty.

But still getting P0132 and P0152 DTC.

Ran OBT Monitor Test and Power Train Live Data readings. Still see 1.27V

Please see attached.
I will install original B1S1 & B2S1 tomorrow and report back.

Thank you

 

[04Liberty#!]

Old S1 sensors re-installed Backpin test performed at idle.

Attached:
O2S pictures and part numbers
Test Results.

Thoughts?

 

[Intermechanico]

Nice work with the troubleshooting, and very nice work compiling the results!

It looks like Bank 1 Sensor 1 is working properly again. Signal voltage fluctuating above and below .5v is what we’d like to see.

Bank 2 Sensor 1 appears to be non-functional. A straightforward way to confirm the vehicle electrical is to swap sensors side to side, B1S1 for B2S1, and see if the problem follows. If it does, you’ll need to replace the bad sensor with a new
NTK 23159 sensor.

A few more technical ways to confirm is to check the B2S1 sensor heater supply circuit with your multimeter:

1) With the old Bank 2 sensor disconnected, set your multimeter to Ohms, connect your leads across the two white wires on the sensor pigtail.
Verification: A good internal heater element should read between 3.5 and 7.0 ohms at ambient shop temperature. If the meter reads Open Line (OL) / infinite resistance, the internal heater element has failed open, confirming the sensor is dead without needing further harness diagnostics.

2) Disconnect the vehicle harness from B2S1. Connect your multimeter black probe to battery negative, and probe the Dark Green/Orange (or Dark Blue/White) 12V feed pin. Since the ASD circuit only powers up for ~2 seconds without engine RPM, this test is easiest with the engine running, but please take steps to do so safely, ideally with tire chocks and a second person to start and stop the engine.
Verification: The meter must read full battery voltage (~12.0V–14.0V). If 0V, trace the harness back toward the rear of the engine where the B2 branch splits from the main ASD power feed, and inspect it carefully for damage.

 

[04Liberty#!]

Thank you
O2 S1 ordered from Mopar NTK 56028994AA ($156)
Will update when installed.

 

[04Liberty#!]

Update
Installed new NTK O2 sensor, in driver's side S1 port.
Short low speed test drive, no codes.
Longer high-speed test drive, ran smooth but long delay when accelerating above 40mph.
Engine light came on w/ Two P0152 codes by the time I got back.

Swapped new sensor to passenger side S1 port.
Short Low speed test drive, no codes.
Longer high-speed test drive, hesitation was gone, no engine light but had one P0132 code.

I don't have the real time code reader today.

Internet gave drivers side as bank 2. Correct?
Code swapped sides with sensor, so not wiring?
I need another new NTK sensor for the other side?

Thoughts

 

[Intermechanico]

Update
Installed new NTK O2 sensor, in driver's side S1 port.
Short low speed test drive, no codes.
Longer high-speed test drive, ran smooth but long delay when accelerating above 40mph.
Engine light came on w/ Two P0152 codes by the time I got back.

Swapped new sensor to passenger side S1 port.
Short Low speed test drive, no codes.
Longer high-speed test drive, hesitation was gone, no engine light but had one P0132 code.

I don't have the real time code reader today.

Internet gave drivers side as bank 2. Correct?
Code swapped sides with sensor, so not wiring?
I need another new NTK sensor for the other side?

Thoughts

Re: Bank Orientation-

First, a quick correction on banks: on the Jeep 3.7L, Bank 1 is the Driver's side ( 1-3-5) and Bank 2 is the Passenger side ( 2-4-6).

The test results nail the diagnosis, but you have the bank orientation backward, which is tripping you up as to which sensor is which.


1. Bank Orientation on the Jeep 3.7L

• Driver side is Bank 1 (Cylinders 1-3-5).
• Passenger side is Bank 2 (Cylinders 2-4-6).
• Cylinder 1 is front driver-side

2. What you Proved -

• Test 1:
  • Driver side (Bank 1): Installed the NEW NTK.
  • Passenger side (Bank 2): Had the OLD/BAD sensor.
  • Result: Code P0152 set. P0152 is Bank 2 (Passenger side). The code flagged on the old sensor side.
• Test 2:
  • Moved the NEW NTK to the Passenger side (Bank 2).
  • Put the OLD/BAD sensor on the Driver side (Bank 1).
  • Result: Code changed to P0132. P0132 is Bank 1 (Driver side). The hesitation vanished, and the code followed that exact old sensor straight across to the other side.

The wiring, PCM, and grounds on both sides are completely fine. The fault followed the old physical sensor across the engine bay.


You now have one brand new working NTK sensor and one dead sensor playing musical chairs. Getting another matching NTK O2 Sensor will complete the job.

Grab a second NTK 23159 for the driver's side, clear the codes/adaptive memory (Fuel trim), and you should be fully sorted.

Don’t forget to report back and help a friend!

 

[DadOSix]

Damn fine work folks!

 

[04Liberty#!]

Understood, Thank you.

Please confirm NTK 23159 is interchangeable with the Mopar 56028994AA.

I will let you know how she runs with the new NTK O2 Sensor

Best regards

 

[04Liberty#!]

Regarding NTK 23159; 3 online parts suppliers post, this does not fit a 2004 Jeep Liberty 3.7L.

New O2 sensor I just installed, that seems to have worked, was Mopar 56028994AA, same as "original".
1st replacement I tried, that did not work, spec-ed by Parts Geek was DriveBolt ST-24253.

NTK 23159 from Rock Auto is 1/4 the price of the Mopar 56028994AA. I like that.
But considering all, I will wait for confirmation on the NTK 23159, before purchasing.

Thank you

 

[DadOSix]

Regarding NTK 23159; 3 online parts suppliers post, this does not fit a 2004 Jeep Liberty 3.7L.

New O2 sensor I just installed, that seems to have worked, was Mopar 56028994AA, same as "original".
1st replacement I tried, that did not work, spec-ed by Parts Geek was DriveBolt ST-24253.

NTK 23159 from Rock Auto is 1/4 the price of the Mopar 56028994AA. I like that.
But considering all, I will wait for confirmation on the NTK 23159, before purchasing.

Thank you

So why not order the same thing you just installed? The mopar one.

 

[04Liberty#!]

Online I come up with these equivalents for the Mopar 56028994AA.
Bosch 18125-315050
DENSO 234-4274
Walker 250-24253
Walker 350-34039
But I am hesitant

 

[04Liberty#!]

DadOsix
Cost.
But that is what I'll do if I don't get confirmation on an equivalent by tomorrow.
Thanks

 

[Intermechanico]

Sorry, my mistake.

Go mopar OE for the win, or roll the bones on NTK 23194 which is apparently a direct cross from the mopar number, and is $42

You must be registered for see images attach

 

[04Liberty#!]

At this point I'll pay the extra $100.00
Thanks for the double check
I'll let you know how it runs when I get it in.

 

[04Liberty#!]

Update:

New Mopar O2 sensor came in yesterday. $175 w/ freight.
I did not run long or test drive due to new DTC
P0302 and tapping sound with light backfire.
This is new issue.

I understand issue is at Cylinder 2.
I will check; plug, injector, coil (all new), cylinder 2 compression, vacuum leaks near Cylinder 2 and report back.

Dang not my day.

Thoughts?

 

[Intermechanico]

Yikes! Not your day at all.

I think you should pull the bank 2 rocker cover as well. Looking for valve train issue at #2 cylinder, Rocker arm jumped out of its cradle or valve not closing properly due to a dropped valve seat.

I’m not sure how this is related to your O2 sensor and fuel pressure issues, but I’ll think on it.