2002 Jeep Liberty - Backwards Oil Pressure Readings?

Specific repair issues for Dodge RWD trucks, vans + Jeep products
Post Reply
CAPLES CAR CARE
Member
Posts: 7
Joined: Thu Feb 23, 2012 10:35 am

2002 Jeep Liberty - Backwards Oil Pressure Readings?

Post by CAPLES CAR CARE »

2nd time here, 2nd jeep concern. 2002 Jeep Liberty

Oil pressure light comes on at 1800 rpm and above. have mechanical gage teed in which shows 65 psi when light comes on. modis shows .37 volts and 0 psi. at idle modis and mechanical gage show same reading. 23 psi. Standard Borg Warner and Mopar sending units used. For some reason, the units work backwards.

Any help would be appreciated!!
User avatar
steven kiser
5K Holy Smokes Contributor
5K Holy Smokes Contributor
Posts: 6184
Joined: Fri Jul 06, 2007 4:58 am
Location: eastern ma.

Re: 2002 Jeep Liberty - Backwards Oil Pressure Readings?

Post by steven kiser »

what is the recent history on this? I'm probably incorrect on this one but i remember two separate senders on some jeep applications.
never argue with a fool, they'll drag you down to their level and beat you with experience
CAPLES CAR CARE
Member
Posts: 7
Joined: Thu Feb 23, 2012 10:35 am

Re: 2002 Jeep Liberty - Backwards Oil Pressure Readings?

Post by CAPLES CAR CARE »

STANDARD PART # PS317 PUT ON FIRST WHEN VEHICLE CAME ON WITH THIS EXACT CONDITION. BORG WARNER PART #S 4191 PUT ON 2ND AND OE PART # 5149064AA PUT ON WITH DEALER PIGTAIL. EXACT SAME RESULT WITH ALL ATTEMPTS. CUSTOMER SAID LIGHT CAME ON LAST WEEK GOING DOWN HIGHWAY AND WENT OFF WHEN SHE PULLED OVER TO CHECK OIL. CAME BACK ON WHEN SHE MERGED BACK ONTO HIGHWAY. BOTH LOCAL DEALERSHIPS HAVE NEVER SEEN THIS BEFORE.
User avatar
steven kiser
5K Holy Smokes Contributor
5K Holy Smokes Contributor
Posts: 6184
Joined: Fri Jul 06, 2007 4:58 am
Location: eastern ma.

Re: 2002 Jeep Liberty - Backwards Oil Pressure Readings?

Post by steven kiser »

As silly as it sounds the pcm may need a reburn or replacement.
never argue with a fool, they'll drag you down to their level and beat you with experience
CAPLES CAR CARE
Member
Posts: 7
Joined: Thu Feb 23, 2012 10:35 am

Re: 2002 Jeep Liberty - Backwards Oil Pressure Readings?

Post by CAPLES CAR CARE »

THATS WHAT I THINK TOO. I GUESS THE GUYS AT THE 2 LOCAL DEALERSHIPS DON'T WANT TO GIVE SECRETS AWAY FOR FREE. I WILL SEND HER TO 1 OF THEM AND POST WHEN SHE GETS IT BACK. THANKS.
User avatar
ricmorin
5K Holy Smokes Contributor
5K Holy Smokes Contributor
Posts: 5967
Joined: Mon Jul 25, 2005 10:11 am
Location: New Hampshire
Contact:

Re: 2002 Jeep Liberty - Backwards Oil Pressure Readings?

Post by ricmorin »

I'm not sure I understand all of your test results. Let's recap...

Oil pressure warning lamp comes on over 1800 rpm.
Mechanical oil pressure is 65 psi when light comes on.
So far, so good. Next you say.....
modis shows .37 volts and 0 psi. at idle modis and mechanical gage show same reading. 23 psi.
Well which is it? 0 psi or 23 psi? This part I don't understand.

This oil pressure sender uses a 5 volt reference, a ground and a return. Have you checked for 5 volts here? Do we have a good ground? And has the signal been verified as it enters the PCM, then compared to scan tool reading? The oil pressure light is controlled by the cluster on this when it gets a low pressure signal from the PCM. I'm not sure what reading you are getting at the pcm when the event occurs.
Ric Morin - Volunteer Forum Moderator, Shop Owner, ASE Master L1
Motorcar Alternatives, LLC
603-622-6434 x203
www.motorcaralternatives.com

I find my life is a lot easier when I use Special Orders
User avatar
steven kiser
5K Holy Smokes Contributor
5K Holy Smokes Contributor
Posts: 6184
Joined: Fri Jul 06, 2007 4:58 am
Location: eastern ma.

Re: 2002 Jeep Liberty - Backwards Oil Pressure Readings?

Post by steven kiser »

Damn, missed that Ric. I was thinking two wire (sensor) not three (sender). A bad ground wire will tank the signal along with the signal wire to the pcm. If either are frayed the signal from or the ground to will cave in and light will come on.

A tip here to caples car care, don't let a test light fool you. I banged my head on a lift post for two days chasing a wiring issue until i got back to basics. Volts carry amps is the way i look at it. With a test light i had 12 volts and a bright light and with an ohm meter the resistance wasn't enough to carry the amp. Under a load it would fail and i found a place where the wire was pierced and 1/2 of the strands were broken. Being old school where each gauge had it's own resistor it was a bit hard to follow.
never argue with a fool, they'll drag you down to their level and beat you with experience
CAPLES CAR CARE
Member
Posts: 7
Joined: Thu Feb 23, 2012 10:35 am

Re: 2002 Jeep Liberty - Backwards Oil Pressure Readings?

Post by CAPLES CAR CARE »

AT 1800 RPMS THE MECHANICAL GAGE READS 65 PSI. THE OIL LIGHT IN THE DASH IS ON AND THE MODIS SHOWS .37 VOLTS AND O PSI. WHEN THE VEHICLE IS AT IDLE THE MECHANICAL GAGE SHOWS 23 PSI, THE LIGHT IN THE DASH IS OFF AND THE MODIS SHOWS 23 PSI. AS YOU RAISE THE RPMS, THE VOLTAGE AND OIL PRESSURE DROP SMOOTHLY TO .37 AND 0 PSI ON THE MODIS EVERY TIME WHILE THE MECHANICAL GAGE RAISES TO 65 PSI.
User avatar
ricmorin
5K Holy Smokes Contributor
5K Holy Smokes Contributor
Posts: 5967
Joined: Mon Jul 25, 2005 10:11 am
Location: New Hampshire
Contact:

Re: 2002 Jeep Liberty - Backwards Oil Pressure Readings?

Post by ricmorin »

Thank you. That makes much more sense. So the PCM sees the voltage go down and the reports the low oil pressure to the IPC which turns the light on. I would next check the 5 volt reference to the switch. See if it remains 5 volts throughout and during the symptom. I would also check signal voltage at the switch and at the pcm with a meter to verify that what the PCM is reporting is actually what it is getting. Also check the ground circuit for voltage drop during the symptom. With that you can rule out any outside influence. If there is no outside anomolies, then it may be inside the pcm.
Ric Morin - Volunteer Forum Moderator, Shop Owner, ASE Master L1
Motorcar Alternatives, LLC
603-622-6434 x203
www.motorcaralternatives.com

I find my life is a lot easier when I use Special Orders
Post Reply

Return to “Dodge Trucks / Jeep”