No start, no dashboard, rest of lights OK

juliecracker · **Posted:** Tue Jun 02, 2015 2:21 am

IGN SW RUN feeds F13, F14, and F36 in Junction Block - trace back from ECM pin 19
How do we identify ECM pin 19? If I count down from 1 the 19th spot is just a hole with no wire/connector inside it.

... to BATT A1 thru C100 (to 8w-10-21) thru 40a F14 in PDC to BATTERY
On 8w-10-21 it shows C100/A106 (from 8w-10-26) connects to F28, not F14. I don't quite follow where to go starting with "thru C100" - F14 connects to BATT A910, which is the constant-on power, isn't it? (that connection is working fine)

- ensure the DVM NEG BLACK lead is reliably grounded in engine compartment and inside cabin
Yes, we've been doing that by testing a known good connection before doing our exploratory tests.

Thanks for the additional specific things to try!

gmctd · **Posted:** Tue Jun 02, 2015 8:12 am

juliecracker wrote:

IGN SW RUN feeds F13, F14, and F36 in Junction Block - trace back from ECM pin 19
How do we identify ECM pin 19? If I count down from 1 the 19th spot is just a hole with no wire/connector inside it.
Correct - C1-19 is blank - C2-19 is power to ECM - ECM connections are split into two sections, two connectors 8w-80-60 is C1 and 62 is C2

... to BATT A1 thru C100 (to 8w-10-21) thru 40a F14 in PDC to BATTERY
On 8w-10-21 it shows C100/A106 (from 8w-10-26) connects to F28, not F14. I don't quite follow where to go starting with "thru C100" - F14 connects to BATT A910, which is the constant-on power, isn't it? (that connection is working fine)C100 is the major interconnection between engine compartment and cabin -
on 8w-30-26 follow RUN-START F944 down thru F14 to ECM pin C2-19 - then back from F944 to 8w-10-26

- ensure the DVM NEG BLACK lead is reliably grounded in engine compartment and inside cabin
Yes, we've been doing that by testing a known good connection before doing our exploratory tests.
Note: you can double-click on the FSM as many times as needed to allow opening several different pages at a time in order to trace back and forth thru various associated wiring circuits - or, just printout each page(s) as I call 'em out - I prefer hard copy so I can mark them up if needed
Thanks for the additional specific things to try!

juliecracker · **Posted:** Thu Jun 04, 2015 3:34 am

We were able to spend some more time on this tonight.

Verified connectivity between:
- ECM/C2/Pin19 and Fuse 14 in JB
- Fuse 14 in JB and BATT A1 coming from the IGN SW (regardless of key position)
- Fuse 14 in PDC and BATTERY (A910)

We did NOT get connectivity between:
- Fuse 14 in JB and Fuse 14 in PDC (regardless of key position)
- Fuse 14 in PDC and BATT A1 coming from IGN SW (regardless of key position)

From 8W-10-21 it looks like it's a direct electrical connection between IGN SW/BATT A1 and Fuse 14 (PDC), through C100. So tomorrow when the light is better I'll take a closer look at C100 (looking at 8W-91-49 and 8W-91-52). From the diagram, it looks like something that can be pulled apart (and maybe needs to be more securely put back together?).

I think this is progress! :-)

juliecracker · **Posted:** Fri Jun 05, 2015 3:42 am

More progress - but shrouded in mystery...

We found the C100 and took it apart - nothing obvious amiss. My husband cleaned and reset the grounds and did some continuity checks while I was at a class - I'm not exactly sure what he tested. Then he put C100 back together and did some more continuity checks (inadvertently repeating some we'd already done); he didn't realize some results were different. While describing to me what he'd done, I pointed out that if we had continuity from Fuse 14 in the JB to Fuse 14 in the PDC then the Jeep should start.

So we went out to the garage - and it started!! :pepper:

We didn't even have to put the battery on the charger. So it appears that the C100 was somehow unhappy or the grounds weren't solid, but there wasn't anything obvious so we're not sure what changed.

HOWEVER, the instrument panel lights and gauges still don't come on. So something still isn't completely right. Tomorrow we'll see if the OBD has power and can tell us anything, and also check the connection and continuity to the instrument panel (since we took apart the dash). And I might try the EMIC self-diagnostic actuator test again, although with no power at all I'm not expecting that to work yet.

gmctd · **Posted:** Fri Jun 05, 2015 5:40 pm

Section 8w-40

juliecracker · **Posted:** Sat Jun 06, 2015 3:08 pm

Thanks again, gmctd. I printed out the diagram and we came down to do more tracking. When I went to probe Fuse 13 I found it was empty - we had forgotten to reinstall the fuse when trying some other test the other day. Popped that puppy back where it belongs and...

IT'S WORKING!!!!!
:pepper:

Thanks so much to all of you guys who have offered suggestions, advice, and FSM diagram pages. I'm not sure how we would have gotten this done without you!

For anyone just joining, the short answer:
It looks like C100 was loose (or possibly the ground wasn't solid due to rust on the ground plate).

gmctd · **Posted:** Sat Jun 06, 2015 11:41 pm

And, once again, logical step-by-step circuit-tracing prevails, where wagging always results in hot pursuit of non-domesticated geese

papaindigo · **Posted:** Sun Jun 07, 2015 7:48 am

I almost posted that you should check fuse 13 but figured that was just too obvious, my bad been there done worse.

geordi · **Posted:** Sun Jun 07, 2015 11:41 pm

YAY!!!!!

No start, no dashboard, rest of lights OK

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