some thoughts.
Unplug the ign coil, jump the connector with a test light, it should flash as engine cranks. 12v on DK/GN wire driver is gray.
the CMP CKP 5v (K25) circuit is also used on TPS and MAP. That WT/BK wire also measure that 5v reference here at MAP TPS.
Maybe try unplugging the TPS and the MAP crank engine and check that flash and 10v spike.

The wire harness at rear of cylinder head where it turns down ( isn't there a stud) type heqd bolt- this often causes a rub thru and wiring issues. ATTACHMENT
Is the AIRbag light on?

 

That was sure quick... Thx.. will try the test light jumping coil connector in a bit.
I have gotten the 10v at sensor connectors, as well as pierce pinned to pcm pin 17(couldn't get the connector cover off to back-probe).
the clips are so stiff I couldn't get them to budge. Maybe a trick to getting those covers off?

The injector harness must be the one you and the certified mechanic mentioned "main engine wiring harness takes a 90 degree turn at rear of cylinder head". I see this one shouldn't be too bad to cut open and inspect. Hope I don't end up at the other big engine harnesses. Do the easier one first I guess appeals to me..

 

its a place to look BUT that high voltage on the circuit will require some checking...
reread my thoughts- MAP, TPS, airbag?

Any recent work, repairs changes?

Diagram shows WHY your tech called the main harness, hope it helps.

 

Just got back in from the garage.
Just saw your last question(air bag lite) it goes on at KO then off after a few seconds as do
all the other cluster lites. ABS lite stays on-don't think it can be related to my issue.

Disconnected coil connector, back-probed both wires, jumped with test lite (tried 4 different lites).
Get NO flash at KO or at crank. Jumped with meter and get 10v @ KO and 1.6v @ crank. Why no lites ??
Hope it's ok to do this jump with meter.
Then connected meter to DG/OR (ASD output) and bat - , 11.2v@KO and 8.2v@crank.
This is where I get lost interpreting these results. Don't know if I should be testing this way
with meter.
Why meter readings but no lites? Lite was connected with good leads, alligator clips to
backprobe pins, used same setup with DVOM.

Pulled the MAP connector, back-probed WT/BK 5v supply wire, with test lite to Bat- , get lite at KO and Crank.
DVOM connected get 5v @ KO and 10v @ crank. Same results with DVOM at PCM 5v pin 17.

Another strange finding, I checked codes @mil and see 12 23 (37times) and no 55. 23 is IAT sensor which I did have unplugged. Should codes stack up multiple times? Dont recall ever seeing a code more than once.
I cleared these codes with my PLX bluetooth scanner, plugged in IAT sensor, cranked over and got no
new codes.

My 66 year old brain is spinning a bit. Been working on this ZJ for 3 months, mostly learning time
followed up with a few hours each day in the garage. Carefull not to do anything that would
be destructive to the PCM. Always disconnect Bat - when unplugging/plugging PCM connectors.
I have 10 pages of testing notes that I review often.
Hopefully the tests in this post make sense to you and can point us to a conclusion...

 

OK the coil wires 1 will have voltage @12v from the ASD, the other (gray) wire goes to PCM and the PCM will ground this to fire coil. Jumping the coil connector with test light tests if the PCM is GROUNDING the circuit - we see this as the test light flashing. You do not see the flashing and confirms the PCM is not controlling ignition, we could also repeat test at injectors BUT they flash fast and a test light may not be visible flashing.

As you are seeing the odd 10v at the CKP CMP and now TPS and MAP - I will look at the wiring diagrams to get some ideas to go on testing. Give me some time - coffee and thinking.

The question about AIRBAG is answered, not a concern. - FYI a AIRBAG issue MAY cause a voltage spike in the TPS, a circuit we are looking at. DONE no problem.

Have you removed the PCM connectors ?

 

I have in the past but they are currently connected..

I have not tested the 10v at CKP CMP, just at MAP and PCM pin 17. Just assumed the 10v would be there also. Thinking about it, bad assumption, considering splices. I figured testing and getting 10v at pcm would be the best test.

also, am I correct in testing the 10v to Battery Negative?

 

5 minutes to think on this- Is my thinking correct?

key on the 5v circuit (K25) is OK
turn to start it goes to 10v.
release key and it returns to 5v.

 

If you are asking me----Is my thinking correct?
I sure think it is.
key on the 5v circuit (K25) is OK
turn to start it goes to 10v.
release key and it returns to 5v.

Hoping you were not waiting for me.
My first shot at this forum stuff, bear with me.

 

My first thought - start simple easy first.
going SLOW testing 1 by 1
The system is OK until going to START so lets look at start circuits.
Remove starter relay - see attachment.
Turn key to start -
Did the K25 reading change?

NEXT
clip test light to 12v source.
with key on read K25 voltage should be 5v.
jump testlight to cavity 10 of missing relay -
Did the K25 reading change?

?

 

How are the grounds(battery to body/engine/pcm)?

 

More advice I didn't take seriously enough..

 

PDF file doesn't open, but I know where the starter relay is, assuming that is what is in the PDF file.
Will do these checks/tests this morning, thx jtek, i sense you have a well thought out plan here.

 

Lines 6-7 in first post---- but thanks for asking!!

Battery cable ends are new, crimp-on, bolted to military terminals. done by me.
All grounds cleaned and good. Alternator cables removed and cleaned.

 

I don't know OBD2 or 4.0, so this is general. The 5v is supplied by an internal power supply inside the PCM. That power supply is regulated and likely uses a floating ground. The internal power supply is completely dependent on the 12vdc system voltage to properly regulate at 5v. I'm wondering what the system voltage is during cranking? The 10v spike *might* be ok is my thought.

 

10v spike OK? this is what caught my eye



Watching this video ( first 2 minutes) resulted in me checking my 5v ref, at the MAP and CKP sensors.
This is when I realized that the 5v jumping to 10v must indicate something is wrong and could possibly
causing my no-spark condition. I then pinned the 5v circuit at the PCM and had the same 10v result.
That is when I compiled my thoughts and started this thread.

New to this forum and first time using "Quote". Lets see if it works. I hope posting a youtube link is OK to do.

 

My results are here. I could not open the .PDF file.(it must show what cavity 10 is)
FYI when I click on PDF link, it opens https://www.jeepforum.com/forum/register.php
I poked around and found cavity 10 corrosponds to relay terminal #85 - Coil ground
I am using a wire pierce at PCM pin 17 WHT/BLK to meter red, meter black to Battery negative.(couldn't get connector cover off)
5.21v at KO, 11.04v at crank (double checked the problem first)

My first thought - start simple easy first.
going SLOW testing 1 by 1
The system is OK until going to START so lets look at start circuits.
Remove starter relay - see attachment.
Turn key to start -
Did the K25 reading change?------------no change, steady 5.21v. With relay out of course it does not crank
crank with remote starter = 11.04v

NEXT
clip test light to 12v source.
with key on read K25 voltage should be 5v. -------yes, 5.21
jump testlight to cavity 10 of missing relay --------relay terminal #85 - Coil ground
Did the K25 reading change?-----------------------No Change, 5.21v and lite is on

Wow-great instructions, my old fogged up brain can even understand. Ready for more...

 

stll here, give me some time....

Are you using a phone to read posts - sometimes they don't show attachments. WHY IDK - thats not my trade

WHan you used remote starter (explain hook up) the reference K25 went to 10volts?

Not getting PCM connectors off will have me regroup..

Tell me how hard will it be to remove wires from starter ESP the solenoid wire?
THe smaller LG/BK green wire?

 

stll here, give me some time....

Are you using a phone to read posts - sometimes they don't show attachments. WHY IDK - thats not my trade

WHan you used remote starter (explain hook up) the reference K25 went to 10volts?

Not getting PCM connectors off will have me regroup..

Tell me how hard will it be to remove wires from starter ESP the solenoid wire?
THe smaller LG/BK green wire?

question #1
Using a laptop - I just tried your pdf link to the PDC relay/cavity diagram 10 minutes ago. now it pulls up your
diagram. Previously, yesterday, 3-5 times, it would pull up the URL to the page that I mentioned above. ???

question #2
The remote starter is hooked up to the starter/solenoid. Only one way to hook it up. get the 10v spike in the 5v ref because the starter is cranking. The test you pointed to earlier was with the starter relay out- therefore no starter cranking with key to start(crank position). Unless I mis-interpreted your instruction, see it here:

Remove starter relay - see attachment.
Turn key to start -
Did the K25 reading change?------------no change, steady 5.21v. With relay out of course it does not crank.
crank with remote starter = 11.04v
question #3
PCM connectors are connected, always have been for all my testing. 5v/10v test is by pinning wire on
connector 3, pin 17, DVOM to battery negative. Not sure how tests could be done with PCM connectors off.
The only reason I pinned wire is because I couldn't get the brittle/stiff splash cover off the connector to T-pin the connector.

question #4
I can easily remove the wires to the starter if you feel it necessary.

Another revalation: Looking back in my 15 pages of hand-scribbled notes, It looks like the 5v/10v ref signal
is being pulled to ground when testing at the sensor connectors plugged in. After watching the video again, I believe the ref 5v should be going back to the PCM with the signal wire, ideally as 5v. In my case it appears to
be going to ground, as 10v, only when cranking with starter. Hope this makes sense...

 

I am going to do the tests again at the CKP connector, just as in the first 3 segments of the video. Test
voltages at the 5vref wire, Ground wire and the signal wire. Re-reading my notes seems like I was getting the 10v back to Pcm on BOTH the ground and signal wires. Possible- will re-test now.

 

no time to explain -
Basically I am trying to find HOW 10v are getting to K25 reference circuit, when you select START. And am eliminating STARTER circuits.

remove starter relay.
disconnect the SOLENOID wire at starter.
Hook up remote starter - you will want to supply 12v to terminal at starter where the removed wire goes.
Observe the reference voltage should be @5v on K25 circuit.
OK now activate starter - what is K25 voltage when cranking?


FYI:
I find reading signal return the 0 to 5v square signal is easiest observed just rotating engine by hand a wrench on harmonic balancer bolt. Plugs removed makes easy, the fast cranking of starter motor and buffer in DVOM can make the signal 'confused' and the DVOM may not shift but freeze at 0 or 5. .

 

I understand where you are going, will do your test now before anything else.
I had done the 0 to 5v square signal test with hand cranking when trying to qualify my CKP and CMP sensors.
Both gave good 0v to 5v square signals with DVOM, dont have a scope. Front end is off my jeep so easy to turn over at damper...

 

Battery cable ends are new, crimp-on, bolted to military terminals. done by me.
All grounds cleaned and good.

Did you check resistance/continuity to the ground terminal/s going into the pcm? I am wondering if voltage is back feeding into the pcm somehow. Might want to disconnect ALL sensors then see what the reference voltage is during cranking. If it stays at 5v then it's a sensor back feeding voltage somehow during cranking. This is why i asked about the grounds.

 

Oh-Boy found something..ground wire

Went to disconnect the SOLENOID wire at starter. Two nuts, pulled the assembly off. Saw and
felt what was behind the 3rd nut (ground-solonoid to starter case, I think) . There was some more
wires attatched there. Took that bigger nut off and found there was a 4wire star connector attached.

I had replaced the starter two month ago and remember it being there and remember cleaning
it with a brass brush and cleaner. Not knowing what it was I put it back on. Now, did some searching and
recognised that it looks like it shouldn't be there. Did some more searching (ZeeJay1997 12 step that I had gone through months ago), It sure looked like a ground. Sure enough it matched up perfectly to the front
coil mount engine bolt that holds the Battery ground. I had cleaned that 4 months ago when I started
this project.

I re-attached the starter and moved that star connector to the engine ground. Reconnected Battery, put
starter relay back in and cranked it over. The 10v surge was gone- 5.21v @ KO, steady 5.29v @ crank.
I thought time to celebrate. BUT, still no spark at COil. Tried my 2 other coils, no spark. Tried my other
PCM, still no spark. 11v with DVOM from coil feed, no flash on test lite when crossing pins @ coil connector.
Back to square one, with hopefully another direction.

With the CKP and CMP testing 5v/0v at reluctor and pulse ring when testing weeks ago, I think
I can rule them out as being bad. CKP is a new Standard Motor Product, CMP is a new SMP and I had
the same results with the original one. I have a new Mopar CKP in the drawer, have it as a spare
for this 1997 and for my 1998 ZJ 4.0.

I question this:
1. Why would a P.O. move this engine ground to the starter ?
2. Why did it run fine for the first 1,000 miles after I bought it ?

I replaced the starter two months ago. I had a 2.3amp drain. Pulled all fuses-no change.
Disconnected Alternator-no change.
Disconnected starter- drain gone. Replaced starter as mentioned above-no drain.

My thanks to jtec, he has been inspirational and pointed me to the starter solonoid. If I hadn't
crawled my 66yr body under there I would have never have noticed the re-located ground.

Reading again what V8GSJJ just posted. I shouldn't assume my grounds are good just because I
checked and cleaned them. Going to re-visit and focus on checking and testing all grounds.

 

One more thing I did wrong.

JTEC, looking back where you asked me how I hooked up the remote starter button and I replied on the starter/solenoid. (Wrong, wrong wrong). I had one clamp on the solenoid post and the other clamp attatched to the solenoid positive. should have had it on the Battery positive.

This in combination with the pcm being grounded to the starter. No wonder ...
Some self-inflicted wounds here, but I do know that I never moved that ground from the engine to the starter.
Was that way when I bought it, but I should have noticed it when I changed out the starter a month ago.
Live and learn, sorry that I wasted so much of JTEC's time.
Still no spark, going to start from scratch now that the 10v surge is resolved. Grounds, grounds, grounds.

 

the 10v mystery is done now there is NO spark...

Where are you checking spark?
Is the coil plugged back in?
Is there 12v at coil?
Is the coil pulsing- jump coil connector with test light..does it flash?

 

1. Where are you checking spark?
Checking spark from coil secondary with coil wire to spark tester clamped to AC bolt. connector plugged in.
I tested this spark tester on my 95 ZJ- it works.

2. Is the coil plugged back in?
not for the following tests. should I have it plugged in and backprobe for the following tests?

3. Is there 12v at coil?
with dvom+ in connector female hole GR/OR , dvom - to battery - =12v @KO/1second 11.v @Crank

4. Is the coil pulsing- jump coil connector with test light..does it flash?
no lite flash when jumping. BUT with dvom+ in GR/OR hole, dvom- in gray wire hole, = 12v@KO 1sec, 11v@ crank. Leads fit in connector loosely so not to damage female pins.
I even clipped lite to DVOM leads= no lite but still showed 12v/11v like above

 

the GN/OR is 12v from ASD.
The GY/WT goes to PCM, this will carry the 12v from ASD and the PCM controls ground on this wire to fire coil. Called the DRIVER wire.
With coil unplugged, you should have 12v on GR/OR, and 0v on GY/WT. Remember that is UNPLUGGED.

Jumping the coil connector with a test light -
You have NO flashing of test light?

If that is correct the CKP is suspect.
Try this - at any injector - one wire is 12v DG/OR. the other* is the DRIVER. Jump the injector connector** as you crank engine it SHOULD pulse flash... This will second check the CKP control.

Have you checked for CODES ?


*colors vary for each injector.
** the injector pulse is fast and a DVOM or test light may not pulse/flash - this is where the NOID light is used - no harm in trying. let me know....

 

First, I read the codes that got set yesterday.
at MIL -- 12 54 54 54 54 52 55 (54=no cam signal during crank 52= rich O2 sensor)
I have the front O2 sensor unplugged, FP relay unplugged, all other sensors plugged in)
On PLX/Torque code reader -- P0340 (Cam sensor A circuit, bank1 or single sensor)

Now your 4 tests:

the GN/OR is 12v from ASD.
The GY/WT goes to PCM, this will carry the 12v from ASD and the PCM controls ground on this wire to fire coil. Called the DRIVER wire.
1. With coil unplugged, you should have 12v on GR/OR, and 0v on GY/WT. Remember that is UNPLUGGED.
@ GR/OR=12v @KO/1second, 11.5v @Crank
@ hand crank=12v/0v matching reluctor holes /CKP, Relays click, Injectors click
@ GY/WT=0v@KO .08v @ crank, @Hand crank=0v/.01v reflecting reluctor/CKP positions.

Jumping the coil connector with a test light -
2. You have NO flashing of test light?
NO FLASH- tried several ways to connect lite to coil connector. ( By myself here)
Seemingly most reliable- I stripped ends of a 20 ga wire, double backed the strands, pushed into
Coil connector, clips on end of wires clipped to functioning small (pen size) test lite
I double checked these connections with DVOM- were good connections.

If that is correct the CKP is suspect.
3. Try this - at any injector - one wire is 12v DG/OR. the other* is the DRIVER. Jump the injector connector** as you crank engine it SHOULD pulse flash... This will second check the CKP control.
Wire strands now wrapped to small diameter T-pins pushed into Injector connector.
NO FLASH @ key or hand crank. hear injectors click @ hand crank..

4.Have you checked for CODES ?
Re checked codes after this session. 12 54 54 42 13more54's 42 54 and no 55
42 is new, = misc ASD/fuel guage and open fuel pump circuit.
Have my FP relay out so I don't have to breath gas fumes from the spark plug holes.
Guessing that's why I'm getting 42, however, didn't get it yesterday( see code list in 2nd line)

On PLX/Torque code reader P0340 (Cam sensor A circuit, bank1 or single sensor) after refreshing

*colors vary for each injector.
** the injector pulse is fast and a DVOM or test light may not pulse/flash - this is where the NOID light is used - no harm in trying. let me know....
I was thinking of getting a noid lite, but with hearing my injecors clicking @ hand crank I didn't buy one.

One other thing I have noticed, the IAC clicks after cranking with key left on. Unplug it and it stops.
I had removed and cleaned it several months ago- it didn't look bad.
Thanks again....