How to check Diagnostic Trouble Codes (DTC) on a JK - Jeep Wrangler Forum

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Old 05-19-2013, 10:05 AM   #1
ilikeguns's Avatar
Join Date: Apr 2012
Location: Long Island, NY
Posts: 736
How to check Diagnostic Trouble Codes (DTC) on a JK

I've seen this posted in a few blogs but I figured I'd post up here on WF for anyone who didn't know this trick.

1. Insert your key into the ignition and turn it to the "ON" position but DO NOT start the engine.

2. While keeping the key pushed into the ignition cylinder, turn it to the "OFF" position and then back to the "ON" position.

3. Repeat Step 2 two more times and make sure it ends in the "ON" position.

NOTE: Make sure you are pushing it in so it doesn't catch at the other positions.

If you do it right, your dash will light up like a Christmas tree and your odometer will show all dashes. If you have any stored codes, it will cycle through them after the dashes. If you don't have any, it will show "-done-".

After that.. do a search for the codes to diagnose the issues.

Codes are a letter followed by four numbers:

The first letter dentes the code is related to
B - Body
C - Chasis
P - Power Train
U - Network

The second is to determine whether it is SAE or MFG.
0 - SAE (standardized code)
1 - MFG (manufacturer specific code)

Third number is for:
1 - Fuel & Air Metering
2 - Fuel & Air Metering (Injector Circuit)
3 - Injection Systems or Misfire
4 - Auxillary Emissions Control
5 - Vehicle Speed Control & Idle Control System
6 - Computer Output Circuit
7/8 - Transmission

The last two are for the specific fault (00-99)
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Old 05-29-2013, 09:09 AM   #2
Join Date: Apr 2013
Location: NC
Posts: 28
I just had my check engine light come on this morning on my way to work. I tried this method but must have done something wrong.
When they say 'On' position, is that the first position when your radio will come on (marked aux on some vehicles), or full on (like about to crank)? The positions aren't marked around the ignition on my 07.
Also, is there a requirement for foot on/off brake or doors closed?

I'm going to run back out and try again after lunch.

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Old 09-13-2013, 10:02 PM   #3
JCROSS's Avatar
Join Date: Aug 2011
Location: Kelso Wa.
Posts: 521
I also tried this method but mine does not light up. I have a 2010 Rubicon
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Old 09-13-2013, 10:18 PM   #4
corvallisbattery's Avatar
Join Date: May 2013
Location: Corvallis Oregon
Posts: 167
First click is acc on, not the one you want. Second click or position is "on". Third is cranking the engine.
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Old 11-04-2013, 10:48 AM   #5
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Join Date: Apr 2013
Location: NE Texas
Posts: 571
I tried this method as well and I could not get it where the odometer shows dashes. Has anybody been able to get this to work on the '13 JKU?
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