My 2000 xj is unable to read codes. When plugged in it does not detect a signal.

I have unhooked my PCM and cleaned all of the connectors and still no luck.

I am having issues with the Cherokee not running correctly and need to fix my DLC in order to solve my problem.

Please any help thoughts or suggestions

 

When plugged in to the DLC, does the code reader/scanner power up (turn on)? Or does the screen say No Communication?

 

Have you tried reading the codes without a scanner? There is a trick to get it to display them on the odometer.

http://jeephorizons.com/phpbb/viewtopic.php?t=2719

 

I think you'll find that the 'key trick' won't work on a 2000 XJ.

 

Key trick def does not work; the scan tool doesn't turn on at all when plugged in.

 

Attached is a schemtic of your DLC and the various modules connected to the CCD Data Bus.

There are several reasons that your scan tool doesn't power up when connected to the DLC. Corroded pin cavities in the DLC or a bad ground connection. Pin cavity 16 is the 2 VDC power tap for the scan tool and pin cavity 4 is the ground circuit for the tool.

First thing to do is to closely examine pin cavities 4, 5, and 16 for corrosion and enlarged pin cavities from Bubba shoving probes in them.

Next, determine if you are getting 12 VDC to the tool power circuit. Using a voltmeter, touch pin cavity 16 with the (+) probe of the meter and pin cavity 4 with the (-) probe. You should see battery voltage. If not try pin cavity 5 with the (-) probe. Still no 12 VDC? Probe pin cavity 16 (+) and then find a clean chassis ground for the (-) probe. If you get 12 volts now, the ground connections at the oil dipstick tube support bracket mount stud may be corroded or not connected.

Pin 16 is powered from fuse 17 in the PDC, but it is unlikely it is blown because it powers the headlamp switch as well.

Let us know what you find.

 

Awesome; thank you. I have to get an electrical tester; only thing else I can think us whether ur not when the tech installed my car starter/alarm if they could have messed up or used part if the wires? I will update

 

Use only a volt/ohmeter when taking voltage/resistance readings. The use of a test light may damage the PCM.

Here's what Chrysler has to say about this:

CAUTION: A 12 VOLT TEST LIGHT SHOULD
NOT BE USED FOR THE FOLLOWING
CIRCUITS, DAMAGE TO THE POWERTRAIN
CONTROLLER WILL OCCUR.

O2 Sensor Signal

 

Not sure if the cig lighter fuse powers it but it does in some other vehicles ive worked on. Check that either way it cant hurt

 

check fuse 17

 

In his XJ, 17 also provides power to the headlamp switch. So if he's having problems with lights F17 may be blown. If there's no lights problems then F17 is probably intact.

 

Lights are good; fuses are all checked under dash n hood. Ground wires are attached n certainly not corroded or rusted @ the oil dipstick.

Getting electrical voltage/ohmmeter tomorrow to do some more diagnosing.

I have an aftermarket alarm/car starter- wondering if something like that could have interfered??

 

So I tested the pins at the DLC and I got nothing for any reading. Great now power. Rechecked all fuses AGAIN; still nada. Traced the wires under the dash for about 7" and they look fine no tampering or issues that I can see.

Thoughts?

 

Did you try "Probe pin cavity 16 (+) and then find a clean chassis ground for the (-) probe. If you get 12 volts now, the ground connections at the oil dipstick tube support bracket mount stud may be corroded or not connected."

 

Yes i did... Not a lot of ideas after that to determine why no power???