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Unread 10-18-2010, 03:40 AM   #1
makim
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Join Date: Oct 2010
Location: chicago
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bought a diesel - need some help code 0504

hi Guys

I recently bought my first jeep liberty (diesel)
But I've been having problems with it right from the start. I invested few hundred and it's runnin ok, but now another code showed up

Brake Switch 0504

Anybody know what it means/.is ?


help

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Unread 10-18-2010, 06:18 AM   #2
GDE
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Posts: 164
This is a plausibility check between the primary and secondary brake switches. One of the sensors detecting the brake being pressed is not functioning properly. There is one sensor near the brake pedal used to detect pedal movement and there should be one off the master cylinder detecting braking effort via a pressure switch, one of these might be having issues. Or if you are resting your foot on the brake pedal while driving, it might be possible to set the pedal movement sensor to '1', while the pressure sensor is still detecting '0', the plausibility fault will set if one sensor is detecting '1' and the other detecting '0' for a long enough time period. Good luck.
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Unread 10-18-2010, 11:37 AM   #3
makim
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Quote:
Originally Posted by GDE View Post
This is a plausibility check between the primary and secondary brake switches. One of the sensors detecting the brake being pressed is not functioning properly. There is one sensor near the brake pedal used to detect pedal movement and there should be one off the master cylinder detecting braking effort via a pressure switch, one of these might be having issues. Or if you are resting your foot on the brake pedal while driving, it might be possible to set the pedal movement sensor to '1', while the pressure sensor is still detecting '0', the plausibility fault will set if one sensor is detecting '1' and the other detecting '0' for a long enough time period. Good luck.

thank you so much for this info

Is there an online pdf manual, where I can find this part and part number?
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Unread 10-18-2010, 11:51 AM   #4
95BadBoy
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2005 TJ Wrangler 
 
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First post - welcome to JF -

Looks like you have some info from GDE for tracking down your P 0504 code.

Some other things to think about that are not related but good ideas for your CRD.

Cleaning your MAP sensor.

Checking to see if there is any fuel weep-age or scoring/melting at the fuel heater plug on your fuel head. It is the right hand plug when looking at the fuel head from the front. If it is the original fuel head, I would unplug it. Been known to cause a few serious meltdowns under the hood and air ingress into the fuel system.

Invest in a real tune to IXNAY the EGR (plus many other things). Really don't want that left fully functional.

Good idea to fill out your Jeeps profile so those responding know what you are working with.
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FS or FT (2) JK Rubi 17" Moab Rims - really nice shape
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Unread 10-18-2010, 04:02 PM   #5
CRD_Joe
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With respect to this forum, youll have more luck looking here:

LOST JEEPS • View forum - Liberty CRD...Love that Torque!!!
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Unread 10-19-2010, 03:35 PM   #6
merlinTec
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Hi
There is a ECM software flash for this DTC there may not be a fault with your jeeps it's just a software glitch.
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Unread 10-19-2010, 04:37 PM   #7
95BadBoy
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Quote:
Originally Posted by merlinTec View Post
Hi
There is a ECM software flash for this DTC there may not be a fault with your jeeps it's just a software glitch.
Does this software flash pertain to the 05/06 models only - or was it also encompassing the earlier 2.5's & later models that you have on your side of the pond?

Just curious is all merlin. Inquiring minds you know.
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05 TJ RME 42RLE with some things
05 KJ CRD 545RFE, GDE Eco tune, Franky II, Al's 4.5 A-arms, JK Rubi Moabs, Silent Armors 245-70-17's, Spidertrax Adapters, Rola Basket, Fumoto Valve, Pinch welds pounded

FS or FT (2) JK Rubi 17" Moab Rims - really nice shape
Need JK Rear Spare tire bracket for project
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Unread 10-20-2010, 01:53 AM   #8
makim
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Quote:
Originally Posted by merlinTec View Post
Hi
There is a ECM software flash for this DTC there may not be a fault with your jeeps it's just a software glitch.
where can I get this flash, is it dealer only?
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Unread 10-20-2010, 06:57 AM   #9
GDE
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This was a very early reflash in October of 2005. The engine ECU part number revved from 56044562CC to 56044562CD. Not sure if the reflash would really help your situation or not. The only change to this diagnostic Chrysler made was to make this fault code a 2 trip CEL verses and immediate CEL. Then again it might help, with this change the fault must be present for two complete driving cycles before the CEL is turned on. A driving cycle is a warm-up, drive and shut down over a certain time period. A dealer scan tool can show you what the part number is inside the ECU, do not rely on the stickers affixed to the ECU.
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