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Is there an interlock system on a 2004 TJ to prevent it from starting?


chino1969

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Is there an interlock on a manual 2004 TJ to prevent starting unless the clutch is depressed or any other type of interlock in the start circuit? I have had this problem on an intermittent basis and can't seem to zero in on the issue. It seems as though the seat belt being fastened may be tied into the circuit but am not certain. Any help or info. would be greatly appreciated.
 

Alex01

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There is a fuse you can pull behind the glove box that will allow the jeep to start without the clutch depressed. From what I gathered online its #20 but the diagram on the back of the glove box will tell you for sure.
 
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chino1969

chino1969

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Well, I took the clutch safety switch out to investigate further. A meter revealed the switch was not making up every time the switch was closed. The contacts were gunked up with dirt and oxidation. I cleaned up the contacts with contact cleaner, Q Tips and contact burnishing stones. Re-installed switch and it appears to be working correctly. Not ready to take a victory lap quite yet as time will tell but am reasonably sure that fixed the problem.
 
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chino1969

chino1969

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There is a fuse you can pull behind the glove box that will allow the jeep to start without the clutch depressed. From what I gathered online its #20 but the diagram on the back of the glove box will tell you for sure.
Thanks for the reply. I considered that but then thought about what effect that would have on the PCM as it controls shift points for an auto. trans. as that fuse is for an auto. trans.. Ended up taking switch out, cleaning contacts and re-installing.
 

Alex01

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I considered that but then thought about what effect that would have on the PCM as it controls shift points for an auto. trans. as that fuse is for an auto. trans..
You lost me. 🤔 If you have a manual I pulled the fuse years ago and haven't had a problem.
 

qslim

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According to the wiring diagram for your year (available in the TJ Resources Section) you have a clutch pedal position switch. Looks like if you install a fuse in position #20 it will bypass the position switch.


98882
98883
 
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chino1969

chino1969

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According to the wiring diagram for your year (available in the TJ Resources Section) you have a clutch pedal position switch. Looks like if you install a fuse in position #20 it will bypass the position switch.


View attachment 98882View attachment 98883
Thanks for that. Check me on my logic if you will. The current path to the starter relay can get there from either the 1) installation of fuse #20 or the 2) clutch safety switch contacts being in the closed position. Fuse #20 is for an automatic transmission.
 

Alex01

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My memory must be a bit shot. I just read up and the process and you ADD a fuse to bypass the clutch sensor.
 
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qslim

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Thanks for that. Check me on my logic if you will. The current path to the starter relay can get there from either the 1) installation of fuse #20 or the 2) clutch safety switch contacts being in the closed position. Fuse #20 is for an automatic transmission.
That's what the diagram shows, yes.. The #20 fuse is applicable to automatic transmissions because their safety interlock is in the transmission range sensor. The fuse bypasses the M/T clutch pedal switch, so it looks like a fuse installed in that slot will eliminate and bypass the clutch pedal safety interlock.
 
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chino1969

chino1969

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There is no fuse #20 in my fuse box either. What I was getting at is power to the starter relay can come from two different paths. One path is if fuse #20 is installed, not removed. The other path is when the clutch safety switch contacts are closed. qslim's circuit diagram (above) shows the configuration. My concern was that the installation of fuse #20 may make the PCM think the vehicle has an auto trans..
 
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chino1969

chino1969

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My memory must be a bit shot. I just read up and the process and you ADD a fuse to bypass the clutch sensor.
Yes, that is what I was getting at. I don't know if adding that fuse would have any effect on how the PCM interprets the data, if at all, but I believe in the simplest solution possible. It appears my clutch safety switch contacts were gunked up and not making contact every time the clutch peddle was depressed.
 
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chino1969

chino1969

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That's what the diagram shows, yes.. The #20 fuse is applicable to automatic transmissions because their safety interlock is in the transmission range sensor. The fuse bypasses the M/T clutch pedal switch, so it looks like a fuse installed in that slot will eliminate and bypass the clutch pedal safety interlock.
Thanks for the verification. I cleaned the contacts on the clutch safety switch as they were gunked up and not going closed every time the switch was cycled. Don't want to take a victory lap quite yet but that appears to have solved the problem.
 
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Alex01

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My concern was that the installation of fuse #20 may make the PCM think the vehicle has an auto trans..
It's safe to add a fuse and bypass the switch. The jeep will try and go forward or backwards if it's in gear and you turn the key but it won't hurt the pcm or make it think it's an auto.
98913
 
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chino1969

chino1969

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It's safe to add a fuse and bypass the switch. The jeep will try and go forward or backwards if it's in gear and you turn the key but it won't hurt the pcm or make it think it's an auto. View attachment 98913
Thank you. I believe my cleaning of the contacts on the switch solved my problem but this is another option.
 
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chino1969

chino1969

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oooo I was wondering I bought mine 7 months ago and it starts clutch in or clutch out....don't make a diff.
Check your fuse panel behind the glove box. If there is a fuse in #20 slot that means this safety feature is bypassed. On a 2004 TJ that fuse is located in the lower left row of the fuse panel looking toward the front of Jeep.