1. Welcome to Jeeps.net!

    You are currently viewing as a guest! To get full-access, you need to register for a FREE account.

    As a registered member, you’ll be able to:
    • Participate in all Jeep discussion topics
    • Transfer over your build thread from a different forum to this one
    • Communicate privately with other Jeep owners from around the world
    • Post your own photos in our Members Gallery
    • Access all special features of the site

positive test for crank pos sensor, finally

Discussion in 'Cherokee' started by 2oldjeeps, Jul 6, 2017.

  1. Jul 6, 2017 at 3:48 PM

    2oldjeeps [OP] Well-Known Member

    May 6, 2017
    98 and 2000 xj's 99wj
    98 lifted, 00 stock 99wj just beautiful
    after reading threads about "which sensor is bad", and changing one only to find its ok,i dreaded doing the cps. i can see it,barely. i can touch it with the tip of my finger, but i dont see me changing one. its too hard to get to...
    i looked at making a blinking led to show the pulses. but first i had to get to the signal wire. no way could i get to the connector.
    i searched the factory manual for wiring up to the pcm,conn c1, found the color coded wire and soldered a short test stub to it.
    now the indicator.
    i had recently bought a small digital o'scope for the price of a good dvm.
    not an expert at it but enuf to actually see and measure the pulses from the cps.
    the book told me that testing the older units should show 200 ohms+- 75 but the new ones should read open! a bad wire could show that si i wanted to see the actual signal in a good runing 4,0 as a reference for future tests.
    the 1st pic is at idle and was at .2v times 10 or 2v per div vertical and 2 ms horizontal division. ill do more to verify this but anyone with scope access could eliminate changing a cps buy probing the cps wire near the pcm connectors,not too bad to get to.

    2nd pix is at higher idle...NOTE PIX REVERSED.

    scope cost me $105, cheep, also measure dc volts.
    next test is cam sensor. to be continued!

    those 3 pulses are as i see it for one crank rotation, 3 sets of notches on the flywheel.
    Attached Thumbnails
    positive test for crank pos sensor,finally-cps-1.jpga cps 2.jpg

    a cps 1.jpg
    chris4x4 likes this.
To Top