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can't hook up scanner off and on no start

postaldave

NAXJA Forum User
Location
kentucky
its a 1996 xj 4.0 auto

i've replaced 3 cps and now on my 4th. this time a mopar one hardwired into the harness.

its running right now but will often shut down like the cps went out again.

i've replaced the coil and cap a year ago.

ive put a new computer in it from a junk yard and that didn't change anything.

it does have a CEL on.

i did the on off thing to get the codes and got some strange numbers.
12, 45, and 56.

i can not get my scanner to hook up to it.

there is no power going to 16th pin on the ob2 port.

my cig lighter has power so it should be getting power to the ob2 port.


im very close to pulling my bumpers and axles and finding a new one and starting over. even had several mechanic friends look at it with no solution.



anyone got anything i can check?
 
I'd check the sensor supply voltage into the Crank Position Sensor or the Cam position Sensor. They share a five volt supply voltage (sometimes 7 volts depending on model). They also share that same supply voltage with other sensors, I've seen at least two different setups. If your supply voltage is the orange wire it shares with TPS, MAP, Cam Position sensor and Crank Position Sensor and the PCM. If you have the violet/white wire setup supplying the 5 volt sensor supply voltage it supplies the crank position sensor, the cam position sensor and something else I'm not really sure of.

I just check the voltage at the cam position sensor or the crank position sensor with the sensor plugged in, key in the run position, If you find like 3 volts you have a sensor issue.

I have a 96 but have never found an FSM for it. I use a combo of a 95 FSM, a 97 FSM and some guess work.

It is not unheard of a sensor short on a completely different branch (circuit) causing issue in the PCM and affecting other seemingly unrelated sensor circuits. The sensor circuit supply voltages to different branches (circuits) are someway internally connected in the PCM. I had an O2 senor with a wire meltdown that was putting 12 volts (heater) into the O2 sensor signal circuit and seemed to scramble thing s up, but never did cause any permanent damage.

Always check to see if the CPS wiring isn't cooking on the exhaust manifold. Do a good inspection, not a quicky. Also check the injector harness where it runs down the front of the motor, And look closely for rub through on the top engine harness.

I had a bad splice going to my ASD relay. I got lucky finding that one and happened to wiggle the harness at the right spot.

I think maybe you are miss counting the blinks on your MIL light when you do the key test. Your MIL codes don't make any sense at all.
 
code 12 is battery was disconected within 50 starts, 45 sis a low volt on one of the o2 sensors and IDK what 56 is. not on the list I have.. 55 is end of list.

I had the same problem with MY Harbor freight scanner. Just wont read my 96 XJ.. Reads daughter #1 97 ZJ,daughter #2s 09 Avenger and Son in aws Chevy p/u NO problem. BUT, the scanner a the smog shop reads just fine. So, maybe its just the scanner. By the way I had that exact sequence of codes.. Found a couple wires the Trans shop didn't hook up. Plugged thos in and reset the computer, disconnected battery.... That cleared the MIL leaving the 12 code for the battery, which it should. This time i didn't get the 56 code I got the normal 55 code. maybe you miss counted like I must have.
 
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