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Go Back JeepForum.com > Models > Jeep Grand Cherokee & Commander Forums > ZJ Grand Cherokee Forum > Check engine light flashing

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Unread 12-26-2009, 07:13 PM   #1
99grandcheroki
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1999 WJ 
 
Join Date: Nov 2009
Location: San Carlos
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Check engine light flashing

1999 Jeep Grand Cherokee 4.0 six-cylinder

My check engine light just went on. I ordered a scan tool and should be able to retrieve the codes soon.

ProScan ISO OBD-II Scan Tool w/USB Interface

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The car runs normally.

From time to time the "check engine light" will flash or blink.

I pulled out the owner's manual to read that this means there is a problem with the catalytic converter.

Does anyone have some experience with this?

I am in California and it seems like most aftermarket converters cannot be sold here. The jeep was not original for California.

Right out of the exhaust manifold, there are two exhaust pipes, each with a bulb. What are these? Pre-converters?

Then the two pipes Y into one and lead to what I know as the catalytic converter. Finally, this leads to the muffler.

Thank you in advance for the advice.

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Unread 12-26-2009, 08:50 PM   #2
JesseOR
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You can pull codes without a scanner. Turn key on, off, on, off, on, off, on, without starting. it should display the codes on odometer
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Unread 12-26-2009, 10:31 PM   #3
97DCZJ
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usually, when the CEL flashes on and off, it means pull over, and turn off the vehicle. it's a warning letting you know something bad is with the jeep
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Unread 12-27-2009, 12:07 AM   #4
99grandcheroki
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Fault code 1494

Quote:
Originally Posted by JesseOR View Post
You can pull codes without a scanner. Turn key on, off, on, off, on, off, on, without starting. it should display the codes on odometer
Thanks for this, I only thought this worked on OBD I vehicles.

I get P1494.

Looking here, Jeep Grand Cherokee WJ - Diagnostic Trouble Codes, I get this:

P1494 (M).....Leak Detection Pump Sw or Mechanical Fault....Incorrect input state detected for the Leak Detection Pump (LDP) pressure switch.

What is the Leak Detection Pump (LDP) pressure switch?
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Unread 12-27-2009, 12:16 AM   #5
99grandcheroki
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Can I reset the codes without the scan tool?

I found a vacuum line that is suspect and would like to see if the code comes back after I fix the line.
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Unread 12-27-2009, 12:21 AM   #6
JesseOR
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Dissconnecting the battery for awhile(30min +/-) SHOULD reset the codes.
That I know works for OBD1 but it should work for yours.

Someone can correct if I'm wrong.
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Unread 12-27-2009, 12:27 AM   #7
JesseOR
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Biggest thing I would suggest, is get a Haynes manual, $24 at AutoZone and will bring you a wealth of info. The one I have covers my '93-'03 or so. I would check but I'm in bed. Lol I can check tomorrow if you don't have it figured out.
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Unread 12-27-2009, 12:37 AM   #8
JesseOR
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I'm bored, pokin around online, here is some info,

Jeep Cherokee Leak Detection Pump

Jeep Repair: leak detection pump pressure switch, jeep grand cherokee, vacuum lines

Just a couple........
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Unread 12-27-2009, 08:38 PM   #9
99grandcheroki
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I found a vacuum line from the LDP that had fallen off of the intake manifold. I replaced it and renewed the rubber connection.

Then unhooked the battery, which did reset the check engine light.

I hit the road and drove constantly for about 200 miles without a sign of the check engine light. But then it went on again.

I checked the code and found P0300 this time. The is called out as "Misfire detected in multiple Cylinders."
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Unread 12-27-2009, 08:57 PM   #10
JesseOR
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Full tune up hopefully will fix that. Hopefully its not a more serious problem.
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