Cranks but no start

[Black99]

1999 jeep wranger automatic with 4.0
Engine cranks over fine but no fire it just dyed on me . There are no codes and when checking for grounds and voltage at the test port under dish there is voltage and ground but no can buss no resistance reading on high or low buss.

[fixkick]

i have 95/ 2008 and sold a 2002 wrangler ( this a huge mistake the 02)
The PCM on this car has an ASD relay. that drops of any of 6 errors happen. ( lost spark,cmp or CMP dead,injector shorts, 02 sensors short,)
First is check all fuses. not blown.
No real scan tool? OBD2?
then check for spark the classic way test. got spark is first, if the PCM sees spark bad, it cuts fuel so FUEL IS ALWAYS last test.
what is the BUSS thing? (can bus?)
this is a 1999 TJ wrangler, I assume USA car, not canada. etc.
I your Full shop manual FSM in hand ,PDF opened now, on my screen.

the 16pin scan tool port at right lower knee, Pin 16 must be at 12vdc for sure key on, of the scan tool going to fail. (only cause is fuse blow to it)
next up if the super secret dash warning lamp for SECURITY key, it is only a RED LED with NO words OR icons AT ALL. STEALTHY,
THIS led MUST NOT GLOW AT THE TIME YOU CRANK THE STARTER. OR ALL SPARK ENDS BY DESIGN (MEANS FUEL TOO)

THE SCAN TOOL MUST SUPPORT obd2 PORT PINS 3 AND 11, jEEPS ccd BUS IT IS.
PIN 7 IS SCI COMMS the scan tool must at least support pin 7.ISO 9141 aka, K-line
Pin 16 dead is fuse 20 blown in PDC fuse box. 10amp fuse.this fuse is hot full time, keyoff too. 12 to 15vdc not less. for sure never less than 10vdc or all; computers in the car go (dump/mad/offline)

the test is use the scan too like this,
its connected and on.
KEY on engine off the too talks to the PCM and shows EPA smog monitor pages, status fully, complete or not complet monitors if not tool bad/wrong tool or fuse blown


with the scan too working
key on,
crank for 5 full seconds
then release the key not off
scan the PCM now.
see DTC p03xx and bingo.
the rule on a dead jeep is, the crank must have turned 10 full spins, turns, to set the error.
5 seconds it does that.

[fixkick]

sorry so late.
Merry Christmas eve to you and all. !!!!

[fixkick]

tell the scan too use? maker and model, I even have scan tool that works on my 95. (Actron and Snap_ON)
this car has no CAN bus. at all
it is CCD (custom jeep comms)
and pin 7 standard data. (if the scan to lacks pin7 , oops) many do.

can buss is p 6 and 14, you have none there, most cars did not until 2004 .
this car is 24 years old, pre CAN bus.

some 1996 scan tools will not work on this car.
some early tools, only do 1 or 5 signal lines.
only newest tools 2008 and newer do them all (on average) I am told, Can bus started in 2007 for the Wrangler.

[fixkick]

the jeeps all have ASD relays 1991 up
this is the no crash and burn relay (purpose)
it cuts spark and fuel
if key (no pun) devices in the EFI fail hard. preventing fuel fires 99%
using a real scan tool most times we can see why it fails, (P03xx codes?) most newer jeeps have DTC error code called ASD overload. mine does.
error 42 ,1995 or P0685 , 1999

Read more: https://www.autocodes.com/p0685_jeep.html
but not always.
we can test the ASD to see if it is dropping off line
the 02 sensor wins the award for killing the ASD< if the O2 heater or wires short , the ASD drops off line. engine dead.
02 sensors or the wires lOVE TO SHORT> it;s their thing !
one simple trick here is unplug the o2 sensor, and crank.
not hot , only engine cold. be safe.