[NYJEEPGUY]

I have a 2006 Jeep LJ Rubicon. I am experiencing the dreaded No Crank/No Start/NoGauges/No Fuel Pump/No OBDII Scanner connection issue. I’m at the end of my rope and unsure what to do.

I feel like I’ve checked everything. Good Battery, all grounds checked, all fuses and relays checked, ignition switch checked good, 12volts to the pink/orange wire in the start position, actuator pin not broken, the starter is good and will jump to turn the engine, New Wrangler Fix PCU with Skim disabled. Also, every engine sensor has been replaced on the Jeep in the last two years and I’ve tried unplugging the Crank Position Sensor and the Cam Position Sensor and there’s no change.

So the Jeep died back in August 2021. I let it sit and messed with it and finally pulled the trigger on a Wrangler Fix PCU in April 2022. I put it in and it didn’t start. So, I let it sit for about three weeks then one day I just decided to mess with it. I checked all the ignition/skim connectors and they all seemed fine. Weirdly, as I was messing with it the gauges came on and it started. I shut it off and started it several times and even drove it about for about 20 minutes. I figured it had to be a loose connection and I “fixed” it. I went out the next day and it was back to the no crank/no start/no gauges again.

I sent the PCU back to Wrangler fix to have it checked out and they said everything was fine.

I have gone back and checked everything I could think of all over again and everything seems fine.

Help! What else can I check?

By the way, I’m not a new forum member…but my account got corrupted and I had to create a new one.

 

[jkp]

Sounds like you have a bad connector or wire in the area you were messing with.

 

[NYJEEPGUY]

That's what I thought, but I've been messing with it for a week and nothing seems to help.

 

[Rubi4MyMrs]

The difference between your dreaded No Crank/No Start/No Gauges/No Fuel Pump/No OBDII Scanner connection issue and the sometimes seemingly similar conditions that often requires a PCM replacement is the no crank. Generally a bad PCM causing the other conditions will not it from cranking.

I’m guessing that is why the PCM did not get it to crank.



You said when jumped it will crank but presumably not start. Exactly how were you jumping it? Did you pull the relay & jump across the socket terminals 30 to 87? Or some other way. If yes, how?

Question, auto or manual trans??

I am looking for a common point that connects all things listed so any more info might help.

 

[NYJEEPGUY]

Thanks for you reply. It's a manual and the clutch interlock is bypassed.

I got it to crank by jumping across the starter with a screwdriver. It's cranks, but doesn't start.

I haven't tried to jumper terminals 30 to 87 yet.

The PCM is a new Wrangler Fix and it was sent back once to verify it's working and to remove the skim.

 

[TheBoogieman]

If all else fails, try a trusted mechanic in NY. I found a local mechanic that diagnoses problems free. If he can't fix it, I don't pay him. Seems reasonable since I can "guess" at problems on forums too.

 

[Rubi4MyMrs]

Assuming the red wire to terminal 30 (1 in the diagram) has 12v (from fuse 6 in the PDC) & jumping to the yellow/grey wire (2 in the diagram) going to the solenoid will crank the engine (but not start) & you said the pink/orange wire (5 in the diagram) does get 12v power when the key is in the start position the last check is if the dark green/orange wire (3 in the diagram) is grounded. Maybe needing the key on, I’m not sure, but that is from the PCM which should ground that wire to allow the relay to close & crank the engine when it senses the clutch is pushed in.

Once you get it to crank or find out why not, you can address it having the No Start/No Gauges/No Fuel Pump/No OBDII Scanner connection.

When you turn the key on, besides the gauges not moving up, do the various lights come on as they normally do or is the cluster more or less completely dead?

Also good to check wires at the PCM connector C-1 (black) for power & ground.

Pin 9 for ground, pin 11 for key on power & pin 29 for constant (B+) power.

Where were you “messing with” the wiring when you got it to start? Under the dash, under the hood along the firewall or in the harness near the PDC?

That might help isolate where the problem is.

 

[NYJEEPGUY]

I'll try the jumper suggestions later today. When I got it to start, I was messing with wiring and connectors around the steering column.

 

[Rubi4MyMrs]

OK, good info.

And the cluster, lights come on when key turned on, or mostly just dead?

It is possible problem involving the ignition switch wiring.

Make sure the connector terminals all look good, well seated & no sign of excessive heat or melting.

Check for 12v power at the 3 B+ terminals in the diagram below.

 

[NYJEEPGUY]

Everything at the ignition switch is good, I even replaced the switch with another one I had just to be sure. Weirdly, pin # 5 Key-in sense only shows 10ish volts. Whether the key is in or not. Good ground too.

Also, I did the 30 to 87 jump in the PDC and the starter cranks...no start.

 

[NYJEEPGUY]

I just checked these pins. "Pin 9 for ground, pin 11 for key on power & pin 29 for constant (B+) power."

Good ground at pin 9, pin 12 12v, pin 29 7.5v.

 

[jkp]

Everything at the ignition switch is good, I even replaced the switch with another one I had just to be sure. Weirdly, pin # 5 Key-in sense only shows 10ish volts. Whether the key is in or not. Good ground too.

Also, I did the 30 to 87 jump in the PDC and the starter cranks...no start.

I believe the key in sense is only for the key in ignition chime. Does that work?

 

[NYJEEPGUY]

Yes, key in chime works.

 

[jkp]

Does you odometer come on when you open the door?

 

[NYJEEPGUY]

Yes, odometer comes one. Dash lights work like they should. With the key in the on position the fuel gauge and volt gauge don't move at all.

 

[jkp]

How did you bypass the clutch interlock?

 

[NYJEEPGUY]

I bypassed the clutch interlock years ago by connecting the ends together. If there was an issue with it....it just wouldn't crank....but the gauges would have worked and it wouldn't prevent the scanner from connecting.

 

[jkp]

Ok, I couldn't remember if it would shut down the pcm.

 

[Rubi4MyMrs]

OK now we may be getting somewhere.

The 7.5v is a problem. That is the B+ (constant voltage) supply to the PCM.

That red wire comes from fuse 9 in the PDC. It splices at the fuse & one leg goes over to the starter relay which is terminal 30 there. Since it apparently cranked the engine well enough that is OK but the other leg goes out from under the PDC in the harness that passes near the battery & up to the PCM.

That wire is probably damaged but not broken since there is some voltage at the PCM. Sometimes there will be corrosion at the splice right at the fuse but most likely there is battery acid damage in the harness near the battery.

If so it should be easy to find & not difficult to repair. If you want to test this before checking the harness &/or splice you could run a temporary jumper from the battery + post to pin 29 just to see if everything is working but pretty sure that is what you will find is the problem.

This does not explain why it was ‘fixed” for a while after playing with wires inside the cab. So waiting to see results after getting a full 12v to the PCM. I do know electronics do not like low voltage so hoping this is the actual fix.

 

[NYJEEPGUY]

OK now we may be getting somewhere.

The 7.5v is a problem. That is the B+ (constant voltage) supply to the PCM.

That red wire comes from fuse 9 in the PDC. It splices at the fuse & one leg goes over to the starter relay which is terminal 30 there. Since it apparently cranked the engine well enough that is OK but the other leg goes out from under the PDC in the harness that passes near the battery & up to the PCM.

That wire is probably damaged but not broken since there is some voltage at the PCM. Sometimes there will be corrosion at the splice right at the fuse but most likely there is battery acid damage in the harness near the battery.

If so it should be easy to find & not difficult to repair. If you want to test this before checking the harness &/or splice you could run a temporary jumper from the battery + post to pin 29 just to see if everything is working but pretty sure that is what you will find is the problem.

This does not explain why it was ‘fixed” for a while after playing with wires inside the cab. So waiting to see the results after getting a full 12v to the PCM. I do know electronics do not like low voltage so hoping this is the actual fix.

That makes the most sense. I did have the PDC out of the mount when I got it to start before because I was checking the wiring. I get there's a corroded wire under there or behind the battery. I will investigate tomorrow. Thanks!