Ethan Winans

I have a 1999 JEEP Cherokee Xj 4.0 L6
i was driving home on the highway doing 70 and my Jeep just shut off so I pulled over and the Jeep would not start back up no gauges at all but the electronic add one all work such as radio, lightbar, rocklights, etc. did some test which later on I bought an ecm which did nothing different. Obd2 reader won’t connect all the powers and grounds are fine tested the loads and resistance on both ends. Tested the resistance on both ends of the cps all good. Scanned the individual modules the transmission module read a code saying Chrysler collision detected engine control failure and this is all being tested with the new ecm and with the old. There is no spark and the fuel pump isn’t turning on will crank but won’t turn over. I thought maybe they sent me a bad ecm so I bought a junkyard one to see if I could get a reading on it and nothing happened.

RocketMouse

"Chrysler collision detected engine control failure"... refers to a data bus collision, not an actual one of course. I'd say something wrong with the ecm. Don't know if the one you got from the salvage yard may have had an issue too.. The no spark or anything else, could be related to the ecm issue.
I don't know if it's caused from a short or something for the power source in the harness going to the ecm. But it would explain why your aftermarket lights, etc. do work as they are probably wired straight to your battery with a switch and are not tapped into the vehicle's wiring harness.
Verifying all of your grounds probably wouldn't be a bad thing to check either... as we don't know at this point what caused your original ecm to fail.

others can chime in, but my vote is try one more ecm that you can verify actually functions correctly before you put it into YOUR vehicle. and see if that doesn't resolve your issue.

Bugout4x4

Do the 99's have an impact switch that might have tripped and need to be reset? I looked but couldn't find anything on a 99 about it.

RocketMouse

^^ anything's possible. I don't think so... but when I pulled the info on the code he said he got, that's what I saw in the research, and Jeeps are not the only vehicles with that issue.
It was listed as an actual data bus issue. What they call a collision is the same thing you get sending data in an IT realm. Data being sent goes down the wrong path for several reasons and literally hits the traffic coming the other direction on over the same segment of the network.
So means there's something wrong with the actual circuitry. Which is why I suggested possibly trying a known good ecm to either resolve the issue or rule it out.

jordan96xj

The Chrysler Collision Detection bus is a simple network that uses a medium of 2 wires with voltages being manipulated to send messages between various components. The code you are getting is likely just saying that it can not establish communication on the bus (or network).

A common cause for this is that another component is presenting voltage on the wires that are used for the bus and knocking out the communications. This can happen when something loses its primary ground connection and makes a jump over to the bus wires in an attempt to ground back to battery negative.

Has there been any dash work lately? Taking the dash apart, putting it back in? Removing trim panels in the driver/passenger foot wells, anything of the sort?

Does the problem remain if you turn the headlights on/off or adjust the interior light dimming switch?

(by the way, the transmission control module is seeing the same thing your OBD2 scanner is seeing, which is a network where communication isn't happening).

Based on what I have seen and researched the 2 likely candidates are an OBD2 sensor (component or wiring to sensors like the CPS, TPS, Camshaft Pickup Sensor, or any of the sensors, typically 3 wires where one is a 5v feed coming from the PCM (computer)) that is failing or shorted. Or a bad ground somewhere, primarily in the dash area (but also could be on any OBD2 sensor).

RocketMouse

^^ nice.
I hadn't personally dealt with this issue before...but at least I wasn't off in checking back for the grounds.

Ethan Winans

I unplugged the cps to see if it was causing the obd to not work would that be a good way to test that?

Ethan Winans

i unplugged the cps to see if it was causing the obd to not read is that a good way to test the cps because when I unplugged it nothing changed

Ethan Winans

Also bypassed the asd relay to the ecm to see if maybe the relay was bad

jordan96xj

Yes, in some cases a failed CPS can take out the OBD2 comms. If disconnecting the CPS results in successful use of the OBD2 scanner, this can be a good indicator that the CPS sensor itself is involved (I personally have helped someone with symptoms like this). Replaced the sensor, and everything went back to normal.

However, if you pulled the CPS and an OBD2 connection could still -not- be made, then it is less helpful. It somewhat rules out the cps sensor itself, but doesn't rule out its wiring. So in effect, it doesn't help rule much out.

Here is what some folks do, they will disconnect all of their obd2 related sensors, and see if they can establish an obd2 connection with their scanner. If they -can- then this helps narrow down the problem to under the hood (between the sensors and the PCM, usually a bad sensor or bad wiring).

If an obd2 connection still doesn't work, then it can indicate that something in the interior is fuzzing up the network bus. These can be hard to track down.

You never did answer the question, has any dash work happened lately? dash removed/reinstalled?

Ethan Winans

just some radio rewiring I removed the back glass defogger switch and the cigarette port on the driver side but left the cigarette port on the passenger that’s it

Ethan Winans

The previous owner cut the 2 front speaker wires so I had to rewrite new ones besides that idk. Kinda raised an eye tho when we did take the dashboard gauges off it looked like someone had pulled the plastic dash apart before but anything past the plastic panel wasn’t noticeable

jordan96xj

Check the ground points that they identify at about the 30 minute mark of the following video. This Jeep starts with the same symptoms as yours. The CCD bus is being knocked out by strange voltage. They climb all over the thing looking for where the voltage is coming from, and ultimately it comes from the basic fasteners that hold the dash assembly to the chassis, which are also acting as the primary grounding mechanism between the dash (and every stuffed in behind it) and the chassis so that it has a route back to battery negative. When the primary ground was missing (literally a loose bolt), the voltage found an alternate route through the CCD (chrysler collision detection) bus and knocked it out (no scanner connection, engine problems).

30 minute mark:

Ethan Winans

Thanks a bunch for the info ima put some of this to the test hopefully tomorrow my Jeeps sittin at the shop so I’ll check these things and let ya know if i find anything

Ethan Winans

i watched a little more of the video and I noticed that thy are able to get reading through their obd and have a check engine light on well I am not getting either of those could it still be a possibility?