Jeep Grand Cherokee - Crank No Start/No Comms

[@andresbarreiro9049]

You must be busy because It’s been a little while. It is pretty simple when you know exactly what you’re talking about. You bring it down to a level everyone would be able to understand. Btw the intro is awesome brings me back to those days when they showed educational videos in school.

[@ScienceOfDiagnostics]

Andres, I have a terrible habit of being overworked.....and then adding 3x as much on top. I've definitely missed out on way more than I've wanted to. Glad to see you here though. As far as an understandable level, I just try to explain it the same way it makes sense to me. The intro definitely reminds me of those old educational videos, except they were way more fun to watch.

[@lonniebrowell2640]

Never heard of a fuse tap. Genius idea man. Learn something everyday. Thanks for the tip. You Rock.

[@garyd.7294]

Dude, thank you for the excellent diagnosis. I've been chasing electrical gremlins in my '01 Grand Cherokee for weeks. It all started with a no crank ,no start. Cleaned all grounds, new pcm ( which was fine for 3 days then left me stranded). I put the old pcm back, topped off the battery cells w/ a charge and no issues except for an occasional amp gauge waver from 13.5 to 14. 5 with all accessories on.

[@mrblonde2013]

Clicked like before even seeing video, know it's going to be interesting. Thanks Chris.

[@ScienceOfDiagnostics]

Very much appreciated. Hope all is well my friend.

[@JerryPrado]

Excellent job teaching us microcontroller basics. I can see how lesser mechanics would start by replacing the ECU. If you pull all the sensors and you still don't have the 5v vcc needed, then check the 5v pin at the ECU connector. If you still don't have 5v, then open the ECU, look for a 3 pin part labeled 7805. This is the voltage regulator that takes 12v and outputs the 5v. If the 7805 regulator measures 12v and ground OK but no 5v, then desolder the 7805 and replace it. That should do it. Also, once all sensors and ECU are unplugged, you should have no reading across the gnd and 5v rails when measuring resistance. If you have any reading then you have a short in the harness. Good luck

[@johnbryson7501]

I want to say thank you because for 6 months I have been trying to understand what the problem was with my jeep and nobody I mean NOBODY explained it like you did and now I really understand what is wrong with my jeep! Thank you again and I subscribed to your channel because I know I will need you again someday!

[@gearheadautomotivel.l.c.5476]

Dude! Glad to see you back here making videos. Thought about you the other day while diagnosing a head gasket failure on a CAT 307D. Was able to use a pulse sensor with relative compression to prove the failure, but wished I had a piezo tach pickup to use for sync. Hope all is going well in your world!

[@ScienceOfDiagnostics]

Easing back into it, I'm too picky trying to make things perfect before posting. I got talked into just rolling with videos a bit more. I hope all is well my friend, I'm looking forward to catching up with you.

[@themadstatist6492]

@scienceofdiagnostics Hey. Excellent video. I'm sure you get lots of people asking for help but I've run into a similar situation with my 2007 Jeep Grand Cherokee. I've taken it to two mechanics and they haven't been helpful. Blamed the immobilizer at first, and then the other garage said the computer needed to be reprogrammed. And the dealerships are being helpful (both in scheduling and cost). If/when you have time, could I ask you some questions based on what my Jeep is doing and maybe point me in the right direction? I need it running and I don't have a ton of money to throw away with a dealer (if I can help it). Anyway, awesome video.

[@SteveAlvarez-o5f]

I bought a 2002 grand cherokee 4.7 4x4 and had the exact problem....it was the camshaft sensor...thanks your video was alot of help

[@Heywoodjablowme420]

Did it throw any codes? How did you decide to change that? I'm not getting any lights on dash

[@High_Tech_Mountain]

Great seeing you brother! Great case study as well! Missed you and your videos! Hope all is well! God bless!

[@ScienceOfDiagnostics]

Hey Angel, long time no see. I got dragged out from underneath my rock and just trying to get some useful stuff out there again. Hope to see you soon brother.

[@weldingjunkie]

Nice to see a video from you brother hope all is well. I have a 99 Jeep Wrangler no rpm , crank no start gotta love the early models putting a steel bolt in an aluminum transmission bell housing for crank sensor lol awesome those engineers. Good to see you brother

[@ScienceOfDiagnostics]

Things are going well. The dissimilar metals doesn't even bother me as much as the fact that you just about need 6' of extensions with 3 swivels and a little magic to get that thing in and out. One of those "I can see it, so it sure ain't gonna be easy to get it out" type deals. Talk to you soon.

[@PatrickMullins-uc9fy]

Thank you for the excellent video, solved my problem quickly, thanks again and again. Exactly what my problem was.

[@JohnSmith-wb6kq]

Excellent vid bro, I noticed on initial crank over no start there was no RPM function on the gauge, called crank sensor then haha

[@DannerPlace]

Very helpful, thanks for posting this.

[@VoltageDropDiagnostics]

Chris! Glad to see you back! Great video!

[@ScienceOfDiagnostics]

Well, you did tell me to stop overthinking and just do it. I appreciate the wisdom as always PJ.

[@lambo300zx98]

I have the exact same issue but I still have both my 5v at PCM. Can the data line keep the PCM from sending ground to asd and fuel pump relay?

[@brentstewart59]

Very helpful. Thanks for sharing

[@joehillard4700]

This was a great video made it simple to understand I just did an engine swap on a 1999 jeep cherokee sport I have fuel cranks no spark or injector pulse dash says no bus any ideas

[@MississippiWopGenius396]

After replacing the fuel pump in my 2006 Jeep grand cherokee laredo 3.7 WK- Im now having a problem with a vapor lock and my new pump is making a ringing/humming noise off and on-is there a way to fix it with a inline check valve or inline filter of some sort. I have to release pressure on the fuel rail to re-crank it after it runs for more than 20 minutes/ which is a possible fire risk which makes it not safe to drive. Any suggestions? Reply

[@oliviamatlock9120]

Hey I’m having fuel pump problems I just got a new pump and my pump is not turning on I have unplugged it and cleaned the plug and tested the relay and it’s still not wanting to prime can u help ?

[@braydenwilks2144]

Did you ever figure it out mines doing this out of no where

[@oliviamatlock9120]

@@braydenwilks2144 yes I did it was a 15 fuse that had blue after i changed it I still had the same problem with just a crank no start so then I found out my cps was bad and she started right up after that

[@officialWWM]

You sir, are a genius!

[@franciscodiez5825]

Great video 👍. Digging the new intro! Good to see you brother hope all is well.

[@ScienceOfDiagnostics]

Things are going well, just busier than I know how to handle. I'm disappointed I missed catching up with you and others at Super Saturday. I hope you enjoyed it and I look forward to catching up soon.

[@jeremykagak3328]

I subed just because you have a cool intro man thanks for the info

[@wannaPreG]

Sometimes you would rethink after a pcm has been change and the system persist, there you will speed up to extra digging

[@jesse24933]

Thank you so much for this video!

[@janetrose6128]

hello I have a 2002 jeep grand cherrokee 4.⁷ can you please show me where to find it

[@letsdothis223]

I basically have the same problem, Crank, no start, no gauge's, no comm, but I do have a 5V reference and my skim light is on. I unplugged all of the sensors and still don't have any communication. What should I do next thank you

[@JF32304]

I recently pressure washed my 4.7 right near the crank sensor and cam sensor, nothing on the top of the vehicle at all. Now I have no comms at all, SKIM/key light is on. I unplug the crank sensor and still have no comms, could I have water further down the wire loom shorting something out? I picked up a new crank sensor and in the process of installing that.

[@scottmclennan6114]

I’ve got a v8 WJ and it won’t even crank at times. I think it’s the SKIM and seems there’s no way to fix it here in Australia.

[@SheepdogPreparedness]

My 03 Grand Cherokee 4.0 is having the crank/no start issue with the Security Key light on. None of the gauges work either. I replaced the crankshaft position sensor, and it did not fix my issue. Suggestions on where to go next?

[@stephenyork8857]

Pcm

[@bravokilo1972]

Great job. I have had my jeep down for 3 years!!😣 took it to 3 shops to no avail. I’m a great mechanic but not as great chasing ghosts and gremlins using high tech thingamajigs.. I’ve replaced two crankshaft sensors (myself of course) on my 1999 WJ inline-6 4X4. Bought it brand knew in 99’. First time I replaced it was probably 2007 with an aftermarket CPS. Then again in like in 2020, aftermarket.. And both times that they died, they died with me actually driving then coasting to a stop! Well I replaced that 2nd bad one with an aftermarket again.. Then only a week later that one went out!! Now no OBD2 comms & no 5v ref.. Sooo I replaced that week old one with another aftermarket!!! NOTHING! So I started replacing EVERY sensor, NOTHING! Ignition switch relay, NOTHING! Cleaning ALL grounds, NOTHING! Tried creating my own jumper 5V reference using a USB cable from watching another KZbinr, Nothing! I’ve replaced the ECM using two different refurbished preprogrammed units using my vin, NOTHING!!! So I sent it to 3 shops and they couldn’t figure it out, NOTHING!!!! None of those shops were electrical shops because the electrical shops in my area were so far behind that I didn’t want my Jeep just sitting there for months risking liability damage to it.. So I towed it back home after it left the last shop. That was a year and a half ago. I just want my Jeep back running, damn! Makes me kinda hate Jeeps now. The dealer said it was too old so I had to use secondary shops because our two Jeep dealers wouldn’t look at it! Another reason to HATE Jeep… The only thing I can Ponder is that my CPS isn’t getting good ground perhaps. After changing that many of them I kinda stripped out the threads somewhat. So I added a little tape around the both to keep it tight. I mean it worked, I’ve done it before and it worked. It’s still tight. Also the CPS bolt receiver area is metal or copper and that tightens against the bell housing. I mean yeah, I wish it made more contact but I never had a problem the other times. No comms, cranks over but no start.. Where would you concentrate? Buying a 3rd new CPS this time Mopar?? Trying to run a self tapping bolt in my bell housing for the CPS? It’s already tight as hell just trying to get the original bolt back in, let alone trying to rig up another bolt or fastener! Hey I’ll pay you for some good advice, what do I have to lose at THIS POINT…😭 All I have is a semi basic OBD2 code reader, about a $150 type unit. And my simple multimeter. And yes I’ve tried unplugging all the things you did in this video and my comms or 5v ref. NEVER came back up. Those shops that looked at my truck NEVER found a bad wire, ground, NOTHING.. BUTTT, They took my word for it (because I bought two new ones) and they NEVER messed around with my CPS (as in removing it). And it only donned on my like a month ago that I had been using tape on the bolt to secure the stripped out CPS. The shops was saying they “think” it’s a bad ECM even though I proved them all with both of my refurbished ECM’s that had warranty on them both, from two different ECM providers.. I kinda don’t think it’s the ECM. But who TF knows….. ANY help would be a God Send!

[@DaileyRiders]

i have this same exact issue with my 2000 grand cherokee 4.0L, it sat for about a year before i got it due to someone hitting a deer with it. when i went to pick it up, it fired right up and i drove it on the trailer myself. when i got home i also drove it off the trailer and parked it. after changing the radiator one day i went to start it and it cranked and cranked then threw the crank sensor code, i’ve swapped the crank sensor on mine 3 times. now it’s just like yours, cranks and cranks, doesn’t fire but also doesn’t give any DTC codes. i’ve also had mine down for roughly 3 years smh. very infuriating.

[@DaileyRiders]

i also agree with you about the ECM bc i’ve also tried swapping mine out 3 times from parts jeeps i have and still nothing. if you find anything out with yours please lmk. i’ll do the same.

[@bravokilo1972]

@@DaileyRiders will do..

[@bravokilo1972]

@@DaileyRiders Wow, this makes me absolutely hate jeeps now.. Especially no assistance from the dealer after they get like 16 years old…

[@DaileyRiders]

@@bravokilo1972 they’re definitely a pain. have you tried a new coil pack? i recently read somewhere that something about the 2000 coil packs differ from 1999 or 1998. i had changed mine from one off of a 1998 cherokee, so i changed it back to the OEM one yesterday and got it to at least pop over when it cranked a few times, now i’m facing a new problem with my key skimmer so fuel and spark are shut down smh. i love electronics. also another thing you could check is your cam sensor/synchronizer.

[@oldschooloutlaw6522]

Does this also work with the 4.7 V8

[@garyd.7294]

Great video, My 2001 grand cherokee has a no start/no crank. Can't figure it out. New ecu/battery, lasted 1 week then left me stranded again. No power.

[@T1C45]

Timing maybe.. possibly crank sensor

[@dedmeat2]

I'm not an electronics guy, i didnt understand ref voltage or how to use it. Might just get my jeep started now lol

[@nickayivor8432]

ACCOMPLISHED Science of Diagnostics My teacher Thank you very much for sharing what you know WELCOME BACK 🙏 🤗 😀 ACCOMPLISHED Science of Diagnostics From Nick Ayivor from London England UK 🇬🇧

[@mikekeough1623]

Nice protocol

[@garybacon7342]

help i have no 5 v reference no comms 1996 zj 5.2 turns over good no spark or fuel press

[@kodiak7438]

Please looking for help. I have a 1993 jeep Cherokee xj . I turn the key to on and crank it but will not start . The only way I can get it to start is to turn the key to on and leave it there in that position until I hear a tic tick tick at the fuse box next to the battery then the fuel pump primes now I can start it this wait time is longer when it is colder out please any help would be greatly appreciated.

[@ElleryTurnerr]

Where are you located at

[@rubenvarela4077]

Does the fuel pump turns on?

[@robertveillon5923]

What happens when you do exactly what you said. I unplugged every sensor and couldn't get the 5v on reference. Please help

[@lesliehoops6749]

Thanks for the info

[@instantcar_pr]

Hi, i’ve same probel to my 1999 wj laredo 3.1 TD, and i don’t see this sensor to remplace

[@joeSmashman]

Thank you sir‼️🙏🏻🙏🏻🙏🏻

[@davecody5997]

What an awesome video bro thank you!!!

[@robertveillon5923]

Hey brother, I need your help

[@robrichardson4418]

very good

[@aundrealiddell7536]

I'm having this problem right now with my 2014 Jeep Grand Cherokee limited right now

[@joelambert9500]

My 2015 started and stalled now it's just cranking I had a historical code for shifter performance something

[@JSmith-k2e]

The fuse is bad? Dont have time to wait on that show scanner

[@hddm3]

Awsome