Tell me if this tracks

"If only EssExTee could be so grossly incandescent" (essextee)
07/20/2020 at 18:14 • Filed to: None

My $500 WJ Grand Cherokee has turned into more of an issue than was originally expected. I finally got a new crank sensor in, only to find that it didn’t fix the non-start issue that literally all the forums agreed was a bad crank sensor.

However, in the course of investigating I think I found a possible explanation. This Jeep might have an aftermarket security system. The signs are subtle but present. First is the mass of non-factory wiring and fuses in the steering column (first picture), including this janky looking sensor ring around the key.

There’s also what looks like a horn bolted up under the hood that’s definitely not present in engine bay photos I can find online.

An aftermarket security system would totally explain the fact that my ECU doesn’t seem to be getting power, but there’s two things working against this theory.

1) I can’t find a control box. If it’s present, it’s hidden wayyyyy in the bowels of the dash

2) The battery harness is untouched, and not a rats nest of taps and splices like you expect from an aftermarket install

This also doesn’t explain the one (1) time I miraculously got this thing to start and run on its own, back before I had it trailered to my house. It’ll also try to start on starting fluid, but sounds like the timing is all jacked up and dies quickly. If the ECU had no power, shouldn’t it have no spark at all?

It’s possible the factory immobilizer system is bad but that doesn’t explain all that weird wiring I found.

So, Oppo, what do you think?

DISCUSSION (21)

MM54 > If only EssExTee could be so grossly incandescent
07/20/2020 at 18:19

#1 is figure out what that tumor of wiring is doing under the dash, and/or put it back to stock.

If only EssExTee could be so grossly incandescent > MM54
07/20/2020 at 18:27

I've reached out to the dude I got this from to see if he can get in touch with the last owner. If there is a second key out there with a security system remote on it, that fixes all my problems immediately.

The Snowman > If only EssExTee could be so grossly incandescent
07/20/2020 at 18:44

Figure out what is not happening for it to run. Air fuel spark compression even if it's the alarm one of these is not there.

If only EssExTee could be so grossly incandescent > The Snowman
07/20/2020 at 18:53

What do you think I’m trying to figure out here? No ECU means no fuel or spark. This isn’t a carbureted classic car. Electronics complicate things.

I have already determined why the car isn’t starting. It’s the ECU not powering up. I have to figure out why that's not happening.

Tripper > If only EssExTee could be so grossly incandescent
07/20/2020 at 19:02

That key sensor is for a remote starter. Something is broken with that aftermarket system, ya gotta get the brain out of there. Somewhere, probably on the column the starter wire will be cut with both ends going to different leads on the harness for the aftermarket security unit. You’ll need to cut and re attach if that’s the case.

Tripper > If only EssExTee could be so grossly incandescent
07/20/2020 at 19:06

The thick gauge wires at the bottom left of the column in pic 1 are where you should look for the brain, all of those wires that have been twisted together are for the aftermarket security / alarm / remote start

If only EssExTee could be so grossly incandescent > Tripper
07/20/2020 at 19:07

The starter still engages as-is, it just cranks and cranks and cranks. I think I have no fuel, because the fuel pump won’t turn on until the ECU powers up.

VincentMalamute-Kim > If only EssExTee could be so grossly incandescent
07/20/2020 at 19:09

I agree with Tripper. That’s pretty clearly an aftermarket alarm system. Add the no start symptom and I would think it’s the immobilizer feature of the aftermarket alarm that’s your problem.

I don’t know how those aftermarket alarms perform the immobilizer trick though. I wouldn’t have thought they’d cut power to the ECU to do it.

I’d guess the aftermarket system’s brain box to be well hidden under the driver’s side dash / center console somewhere.

I have no idea how you got it to start that one time. But the simplest explanation is the aftermarket system.

The Snowman > If only EssExTee could be so grossly incandescent
07/20/2020 at 19:13

Well not sure why you're asking for advice if you're going to respond like that. Good luck.

Tripper > If only EssExTee could be so grossly incandescent
07/20/2020 at 19:17

Hm ok yeah there’s nothing that goes from an aftermarket unit to the ecu to the best of my knowledge I used to install them. Sometimes you have to tap into those weird Modules in GMs and Fords but never engine Mgmt.

One more thing you might check is the tach wire, that is how most of those aftermarket units tell if the engine is on. If the Ecm is t turning on though, that prob won’t help.

If it were me I’d yank thank security system and trace back all the wires. I have seen some god awful installs.

red_ > If only EssExTee could be so grossly incandescent
07/20/2020 at 19:19

The ring is to provide an antenna for the programmed but usually uncut Sentry Key that should be hidden further up the steering column . The box is maybe around 3 inches long and 1.5-2inches wide.

Echoing other folks, I’d start at the wiring harness by the ignition switch and removing everything not factory attached to it.

When you key on, does the Sentry Key light turn off? Its up in the top right of the cluster. If its happy with the key, it should turn on, then off, else it’ll blink.

If it doesn’t like the key, it’ll run for 2 seconds then die, but it’ll run like normal

Victorinoo > If only EssExTee could be so grossly incandescent
07/20/2020 at 19:31

I’m with the snowman on this one. How do you know for sure that your ECU isn’t getting power? Did you get to the ECU and back probe the power pin? (which assumes you’ve pulled up a wiring diagram)

If this is the case the use said wiring diagram to find wh at circuits are on the ECU power feed. Check the wires for integrity and go from there. But I too am very curious as to what steps you’ve taken to condemn the ecu. Bc it looks like you took a shot in the dark and changed a crank sensor for no reason.

If only EssExTee could be so grossly incandescent > Victorinoo
07/20/2020 at 19:36

I have a specific combination of dash lights that forums say means the ECU isn’t powering up, and a scantool can’t connect to it.

A specific and common issue with with these cars is that bad crank sensors cause a PCM fault that (dot dot dot) causes the ECU not to power up.

I’m just really sick of people assuming I don’t do my research or know the basics of how cars work. “well maybe you should make sure you're getting spark, fuel, and air ” thanks sherlock that was really helpful

If only EssExTee could be so grossly incandescent > Tripper
07/20/2020 at 19:53

Kinja'd!!!

Well I just found this tucked up behind the main fusebox, along with another mass of wiring. There’s no branding on it but it’s gotta be the control box.

It’s gonna be a nightmare trying to figure out what wires are supposed to be there and what were added.

Victorinoo > If only EssExTee could be so grossly incandescent
07/20/2020 at 19:54

If you’re certain ecu isn’t getting power then why don’t you run power to the ECU and see if it fires up? Just be sure to use a fuse inline in case you accidentally short the wire . This will answer your question.

If I were you I’d pull a wiring diagram Up. With the wiring diagram work your way backwards to the ignition cylinder, find the wire color that has switched power that feeds the ECU and then follow it to the culprit.

Tripper > If only EssExTee could be so grossly incandescent
07/20/2020 at 20:00

Probably nothing has been “ added” those things come with multiple harnesses for everything. However it does look like it has been splice/tapped/tapped every which way which is annoying. That looks like a “Code Alarm” brand, I am less familiar with them than I am with units from Directed Electronics (Viper, Python, etc...)

Happy to help if you’re like WTF is this wire etc...

Still it’s weird that your ECU isn’t getting power. Seems like that is problem number 1.

The only things you need to be weary of before removing that alarm unit is the starter wire and power door locks. Sometimes installers cut the factory door locks instead of tapping in and unplugging the factory keyless entry module. If you unplug that brain and the door locks don’t work that is the issue. Not sure where the factory keyless in a jeep is but its likely in the drivers side kickpanel or way up underneath the drivers side dash (you can hear the relay click when you lock or unlock).

If only EssExTee could be so grossly incandescent > Tripper
07/20/2020 at 20:09

I unplugged the box and the factory remote still works

Victorinoo > If only EssExTee could be so grossly incandescent
07/20/2020 at 20:23

Not sure why I decided to be this helpful, especially as you have not listened to others’ advice here but here you go: https://www.ifixit.com/Document/AYXaimFhCYKGDW5d/Jeep-WJ-Service-Manual-.pdf

check page 686 it has a power distribution diagram for the PCM.

Thisismydisplayname > If only EssExTee could be so grossly incandescent
07/20/2020 at 22:04

You’ll have to take each wire out and try to find the two ends of they cut them, then reattach. Could be they cut a ground to the ECM, or it broke over time. That could explain why it doesn’t get power. Do you have a pin out for the ECM to check if it’s getting power? I just swapped out my old remote start and installed a new one and it sucked to clean up the wiring. But those posi lock connectors make it easier. Then you can test connect wires and switch them if need be.

Kinja'd!!!

If only EssExTee could be so grossly incandescent > Thisismydisplayname
07/20/2020 at 22:05

I found a pin-out diagram for the ECU but access is almost as difficult as removing this alarm panel is going to be.

Thisismydisplayname > If only EssExTee could be so grossly incandescent
07/20/2020 at 22:13

Gotcha. Well once you are able to pull out the box and untangle the wires, it shouldn’t be too crazy. Just need to be patient. And if you cut a wire and don’t have the other end, try leaving a bit of the added wire on the cut so you can match up wires. I case you have a bunch that are similar colors. Good luck.