Motomatt14

It hickup when starting but will never actually start. I've changed the PCM, TPS, map, distributor and cam sensor, cap, rotor, new battery. I only get spark on #1 and #6. White wire to coil says I'm suppose to have 12v constant, but I dont have any voltage until I start to crank it. Help!! Please and thank you

CCKen

Here's the '99 diagram for ignition, crank, and cam sensor (below).

The Gray wire from the PCM to the coil is the coil (ground) driver and the Dark Green/Orange tracer wire is 12 Volts the power input to the coil from the ASD relay.


When the PCM sees an engine rotation signal from the crank sensor it with activate the ASD relay - powering the coil.


The crank sensor sees three sets of 'windows' in the flex plate which trigger the signals to the PCM. The crank sensor signals are paired, in terms of which cylinders are ready to fire. The companion cylinders are:
1-6
5-2
3-4


The cam sensor is supposed to sort out exactly which cylinder is ready to fire, and sends these signals to the PCM.


If the cam sensor is not receiving the 5-2, 3-4 signals it goes stupid and nothing happens when those cylinders are ready to fire.


I suspect your crank sensor is defective (weak magnet [?]).





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Roadking_

sounds like a good trouble shoot to me

Motomatt14

So it turns out that when I swap the PCM with my other Jeep that's a 2000 it doesn't work. I thought they were the same same plug same location same everything but they don't work and when I swapped in the blue Jeep stopped working. So I put the original PCM back in the white Jeep which is the one with the one and six issue, and cleaned the four grounds that I knew of and it fired right up. I did a few drifts and burnouts down the street and then took it on the highway. Once I hit about 50 miles an hour it shut off and now it won't start again. Not even a hiccup. My scanner says it's a P0122 code for throttle position sensor. The sensor is brand new. Now once again I am completely stumped