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Unread 08-18-2011, 11:49 AM   #16
stenyeart
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1990 YJ Wrangler 
 
Join Date: Sep 2007
Location: Lewiston, Idaho
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I undertand that.

Here is the problem, no ground to sensors. I know this because I can check the 5 volt supply with a body ground, but not with the sensor ground in the connectors. Wiring from sensors to PCM is good. Ground supply for computer is good.

My question is, does the computer always supply the sensors with ground or does it control the ground. If it is controlled, what triggers the computer to supply ground?

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Unread 08-18-2011, 02:08 PM   #17
Que89YJ
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1989 YJ Wrangler 
 
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Pm sent call me
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Unread 08-19-2011, 10:52 AM   #18
stenyeart
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1990 YJ Wrangler 
 
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After much help from Que89YJ and a few days with a DVM glued to my hand, it runs.

I ended up putting a jumper from ground to the sensor ground. This provided the ECT, TPS and IAT sensors with the ground it was missing.

I then disconnected the battery to clear the codes.

When I tried to start it, I was getting the following codes:
12 - Battery disconnected
11 - Cam or Crank Sensor
55 - End of Message

I have aleady replaced the crank sensor, so I backprobed the Cam sensor, it tested good.
At this point I decided that I was going to do the same to the Crank sensor to check for signal.

The ignition was in the on position, when I grabbed the connector for the Crank sensor, the fuel pump primed. I noticed that I could get it to cycle on if I moved the wires around. Had the wife crank the jeep while I wiggled the wires and she fired right up (the jeep, not the wife).

Once again, big thanks to Que89YJ for all the help.
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Unread 08-19-2011, 10:59 AM   #19
dtn8tr
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Nice job...you too Que! It seems that most of the more frequent issues boil down to the crank or cam sensor.
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Unread 08-19-2011, 12:00 PM   #20
Que89YJ
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1989 YJ Wrangler 
 
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This is the info on the VSS you need:

VSS is the vehicle speed sensor. You have a cable that goes to the cluster but the newer 4.0L need the speed output. The later models 92-95 had a electronic cluster that receives the speed from the ECU. The 87-90 were all cable driven. The 91 YJ had a combo along with the list post on the link.
Here is a list on a post of all the vehicles that use the combo sensors that should work:
http://www.jeepforum.com/forum/f12/91-vss-any-other-vehicles-have-1095229/

Here is a links for you to read through:
http://www.jeepforum.com/forum/f12/4-0-swap-vss-connection-963222/
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Unread 08-19-2011, 12:51 PM   #21
Que89YJ
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Wiring for the VSS

http://www.jeepforum.com/forum/f12/9...20/index2.html
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Unread 08-19-2011, 01:59 PM   #22
oldtime_ironman
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Way to go guys! Ya did it!
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Unread 08-19-2011, 09:31 PM   #23
johnny27030
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1991 YJ Wrangler 
 
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Location: Mt Airy, NC
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Not sure about a jeep but I know on some of the later model vehicles the oil pressure switch controls the fuel pump after that initial 3 second prime. It made to shut the engine off in a crash if the engine looses oil pressure. Like I said not sure if it applies to this model Jeep or not, but if so ide check that oil pressure switch\sensor!
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Unread 08-19-2011, 09:33 PM   #24
johnny27030
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nevermind. Didnt see the second page of replies
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