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flash2225 07-21-2013 07:02 PM

Non Start Jeep Grand 93
Hey everyone,

Im at a loss here. I have a 93 Jeep Grand Cherokee 5.2 L

While driving my Jeep the other day i get a Check engine light that popped on, immediately i noticed a voltage drop on my gauge, and the car began to sputter, bucking and wanting to die in the middle of an intersection. I was about 1 mile from home, and wound up limping it to my driveway (thankfully).

I got the OBD code for a bad TPS sensor. No problem easy fix. I go down to autozone grabbed the new TPS (duralast), and install it without issue. I turn the key in the ignition, the car fired over and died about 1.5 seconds later. I attempted to start it again but the motor just cranks and cranks but wont fire.

I figured its possible i have a bad battery/connections. Get new connections for the terminals and have the battery tested. Those are all good. I attempted to start the car again, same thing. Crank but doesnt fire.

Out of curiosity i take off the new TPS sensor and put back the old one. Last time i tried to start it with the old sensor it started, but just ran like crap. Same thing, car cranks wont turn over.

Checked spark plugs and wires - good
Had replaced cap/rotor etc 1.5 years ago
Checked air filter - good
Checked alternator - good
Hooked the car up and tried to jump it - check
Disconnected battery overnight thinking the computer may need to reset.
Fuel filter - its good
Checked to see if it was getting fuel to the fuel lines - check

At this point i am out of ideas. Has anyone come across something similar, or have an idea of what to do next. I did a search on multiple forums and couldnt find a problem that was exactly like mine. I did see that some people say that the after market TPS sensors are crap. Any ideas or clues would be much appreciated.

(i hope i posted this in the right section, my apologies if not)


JasonStebbins 07-21-2013 07:15 PM

My money is on a bad battery, bad alternator or failing PCM.

Check all your grounds too.

zjosh93 07-21-2013 07:28 PM

Start by checking for fuel and spark. I give the throttle body a good shot of brake cleaner or carb cleaner to see if it's a fuel issue. Then I like to pull a wire and put a spare plug in it. Lay it on a metal part to ground it and have someone crank the engine while you watch for a healthy bright blue spark. Once you know what you lack it's easier to find the problem.

When I got my ZJ it would eat a coil every year. The symptoms you have sound just like a bad coil. They would usually have spark but it would be yellow and weak.

dellis 07-21-2013 08:10 PM

I am assuming your battery and its connections are good, as you report.

If this were my Jeep, there are three parts that I would be testing to see if they are good: the coil, the crankshaft position sensor (CKPS), and the PCM - any of these might cause a no-start condition. And, because you received a code concerning your TPS, I would also be testing my 8V reference circuit for a short ... the TPS would not cause a no-start condition, but because it shares the 8V circuit with the CKPS, it is a concern.

If you want to guess at parts that are causing your problems without diagnostics, here is the list of things it might be (based on other's experiences).
  • Because your Jeep failed with that stuttering and THEN had a no-start, the CKPS is highly suspect. Probably about a 50% chance this is your problem.
  • A failed coil might cause weak spark that would help you limp home, but that seems odd. Still, given the age of your vehicle it might not be a bad general maintenance item, and (who knows?) it may solve your issue. Chance of success here is about 10%, but it will run smoother with the new coil.
  • The PCM could also cause the quick stutter and fail, but it is less likely than the CKPS ... probably about a 30% chance that this is your problem.
  • Everything else, including wire and connector problems, ground problems, etc make up the other 10%.

But, if you want to diagnose your problem using a series of tests, then here you go (these tests may have a small error or two, so report results if you are taking this approach to ensure your conclusions are correct):

Critical voltage tests
(1) While cranking your engine, do you have 12V present on the electrical connector of any fuel injector? Disconnect the electrical connector, and put a meter between the dark green/orange and a ground point (the engine block).
(2) While cranking your engine, test for spark through any of your spark plug wires.
  • Test 1 passes, Test 2 fails. You likely have a bad coil. Test the coil and replace if bad.
  • Test 1 fails, Test 2 fails. In this case, critical voltage is not being supplied to start your engine. Either the PCM is not activating critical circuits to start the car, or the ASD relay is defective. Go to test (3).
  • Test 1 passes, Test 2 passes. In this case, you need to go back and check fuel pressure because you most likely have a fuel problem.

ASD Relay Test
(3) Switch your ASD relay with a known good relay, say the horn relay. Attempt to start again.
  • Jeep starts. Your ASD relay was bad (or terminals corroded) and you have finished diagnosis.
  • Jeep does not start. The PCM is not activating critical circuits to start. Go to test (4)

CKPS Tests
(4) With the electrical connector disconnected and key in the "on" position, verify voltage to the CKPS from the PCM. It should be 8.0 volts for 1995 and earlier vehicles. Test between the white/black (voltage) and the black/light blue (ground) wires. If it is not 8.0 volts, then there may be a short on the 8volt line, or the PCM is having problems.
  • 8.0 volts not present. You either have a short on your 8.0 Volt line, or your PCM is not generating 8.0 Volts. Go to test (7)
  • 8.0 volts present. Your voltage supply to the CKPS is good, and you do not have a short. Go to test (5).

(5) Next check for damage to the CKPS ... place an ohmmeter across terminals B and C of the CKPS connector. The meter reading should be very high or open (infinite resistance).
  • Test fails. If you notice low measurable resistance, then the sensor is bad. Replace the CKPS.
  • Test passes. If the resistance was very high, typically above 10,000 ohms, then the CKPS may still be bad so we will need to do another test. Go to test (6)

(6) Reconnect the sensor and put a scope or meter on the signal line. Remove the plugs and attach a breaker bar and socket to the crankshaft pulley center bolt. Turn the key to the "on" position and slowly rotate the engine a full rotation while watching the meter. On a 5.2, it should dip from 8.0 volts down to ground every 45 degrees as it hits the notch on the flywheel.
  • Test passes. If tests (4), (5), and (6) have all passed, then your CKPS is good. At this point, additional testing would need to be done with the PCM, its connectors and wires to be certain ... but, probably, you have a bad PCM.
  • Test fails. If it is giving you other readings, then you have a bad CKPS. Replace it.

8 Volt Supply Testing
(7) If you are at this test, then you are not seeing 8 Volts being supplied to your CKPS. Disconnect the electrical connectors to your MAP, TPS, and Camshaft Position Sensor (CMPS, connector to your distributor). Repeat the procedure in test (4) above.
  • Test fails. If 8.0 volts is not being supplied to the CKPS after disconnecting these other components, then your PCM, its connectors or critical wiring is bad. Most likely, your PCM is damaged.
  • Test passes. If 8.0 volts is now present to the CKPS, begin connecting the MAP, TPS and CMPS one at a time ... if, after connecting one of these components you notice that the 8.0 volts disappears, then that sensor is causing a short and needs to be replaced.

flash2225 07-21-2013 09:33 PM

Thank you for the responses, i appreciate it. Ill hopefully get a chance to work on it tomorrow. Ill update what i found. Thanks again.

ErikTheRad 07-21-2013 09:55 PM

Coils fail. Even new ones, as I just learned the hard and expensive way a couple weeks ago. (Had to get towed off I-80 with entire family and camp trailer in tow.) The jeep acted almost exactly as you describe, it was failed coil fhat was less than 2 years old. Buy a coil for $30 and plug it in. If that isn't the issue, its ok..... you would likely need a coil soon anyway.

zjosh93 07-21-2013 10:07 PM

The first three years I had my ZJ I went through a coil per year. Stock, parts store, parts store, Accel. I made a bracket to move the coil away from the block and up behind the ac compressor. Bought a MSD coil and it's been in there for four years.

Concolour 08-10-2013 06:06 PM

Subscribed so I don't have to use search every time the app resets. That list of tests is being useful lol

flash2225 08-19-2013 09:39 PM

Sorry i havent been back to update my thread. Some family issues that i wound up having to take a week out of town, and work getting in the way of spending any time on the jeep other than 20 min blocks.

I finally got some time to work on it (and a helper to crank the engine while running tests)

Went down and got the battery checked again. Again it checked out fine.
Swapped the ASD relay and still didnt start.
Proper voltage at fuel injectors.
If i remember correctly had 45 PSI on the fuel rail.
Went and bought a new coil wire, just because well as someone said earlier, general maintenance.
Tested for spark, had spark.

I didnt get to the CKPS test, i was certain that it was going to be the issue. So i headed out to the junk yard and was going to pull one, just to test. Wound up not finding one that was in good shape, or that was accessible, but i did find a new throttle body. Figured eh for 20 bucks ill buy a new throttle body (with IAC, MAP and TPS with it) clean it up and save the CKPS for another day. Cleaned up the new throttle body, installed it, and finally after a few cranks, the Jeep started. Ran like absolute crap, exhaust EVERYWHERE, rough idle, and then would finally die. But it would start right up again.

New codes were the MAP, TPS sensor. So i took my MAP off of my old throttle body and installed that. It ran a little better, then took my new TPS sensor that i had purchases and installed that. That made it run a little better again. So then i figured, it must be the IAC now! So i took that off my old IAC, cleaned it, and installed it. It ran worse and gave me new codes again .........

Code 46 - Battery Voltage to high
Code 21 Oyxgen sensor feedback circuit
Code 23 Air Charge or Throttle Body temperature voltage HIGH/LOW-charge air temperature sensor input is above or below the acceptable voltage limits
Code 14 Fault in MAP circuit

So i have a few questions on these codes. The battery voltage is to high, is that because the car has been sitting so long, and the voltage has had nowhere to go?
On the Oxygen sensor, am i correct in my knowledge that the 93 5.2 only has 1 o2 sensor, and this could have been fouled by running it home, and then starting it back up?
Is the code 23 for the throttle body have to do with the IAC? Did i break the IAC pintle?
Still throwing a MAP code? Anyway i could have fouled that now, or could this be a false code given how bad the jeep was running after start up?

Sorry about the format, posting from my phone with greasy hands

Rich93ZJ 08-19-2013 10:49 PM

Did you replace all of this with your battery connected? If so, you need to pull the battery + off for about 30 min to let the pcm relearn. If at this point it runs then you are a lucky man. as for the map sensor error, make sure you connected the little vac hose to the barb. I am still thinking you have an issue with the cps though:thumbsup:

flash2225 08-19-2013 11:04 PM

Hehe yeah i did make sure to have the battery disconnected while i did the "repairs". I may however, did not have it off for 30 minutes to be honest. Ill go pull it and let it sit over night. I did swap out another MAP sensor, and that seemed to help a bit, it also cleared the code. I am actually down to 2 codes now, the 46 (battery voltage) and the 21 (o2 sensor). I am hearing some sort of air leak on the engine now from somewhere (maybe didnt seat the IAC right, or bolt it in tight enough as that's where the sound is coming from).

I also noticed some exhaust now coming up through the engine compartment, i know i have a crack in the exhaust pipe (someone did some "repairs" to it) and have not got around to fixing it yet. So i am wondering if its just drifting up through there.

As far as an issue with CPS Rich, i was lead to believe (reading other threads) (and through some friends with "knowledge") that if it was the crankshaft position sensor, i wouldn't be getting spark or fuel? Is that accurate? I think that may be my next job just to get it done, and rule that out for any future issues.

I do really appreciate all the feedback and replys to this thread. I also want to apologize for taking so long to update my thread. Many people here spend there time helping people, and i'm sure that there are posters that just don't bother to show back up and post their updates, that could in the future, help someone else. So, again thank you all that have taken the time to reply.

Rich93ZJ 08-20-2013 01:34 AM


Originally Posted by flash2225 (Post 15814136)
As far as an issue with CPS Rich, i was lead to believe (reading other threads) (and through some friends with "knowledge") that if it was the crankshaft position sensor, i wouldn't be getting spark or fuel? Is that accurate? I think that may be my next job just to get it done, and rule that out for any future issues.

When mine was going bad it would randomly stall which felt like I turned the ignition off. Sometimes it would fire right back up, sometime it would have to sit for an hour then try to fire but it would run like it was on half the cylinders and eventually clear itself up. I never once got a code or any indication that it was the cps. After installing the new (Mopar) cps, the jeep has not skipped a beat. I'm not saying this is the fix for your jeep but a lot of people on here experience very strange symptoms from this stupid sensor. One thing to consider, The crank sensor in conjunction with the cam sensor are the primary timing for the fuel injection in your vehicle. If one of those are out of sync, you will experience what you are describing. If you consider replacing the cps, get a hold of He is the resident parts vendor here and will always get you a competitive rate. Don't go the cheap route on this sensor. Mopar only. You will pay a little more but its worth it in the long run. Good luck with the repair. Hope I helped a little. I would love to know the outcome so keep us updated. :cheers2:

After re reading all of the posts, try to disconnect the o2 sensor and see if it runs any better.

flash2225 08-20-2013 09:28 AM

Thanks Rich!

I think i will wind up just replacing the CPS as a general maintenance thing over the weekend. And thanks for the heads up about I plan on only going Mopar in anything i do as i go through this thing.
Ill disconnect the O2 sensor when i get home, and see what that does!

flash2225 08-22-2013 06:37 PM

Well, i think its finally problem solved. I hope this is a lesson to others, as i know i sure learned something. I have done very very little work on cars in my past, so things that may be common knowledge, are not to me. If the car was a computer (well it sort of is now that i had my first major foray into fixing one) i could build it from scratch and diagnose any problem.

So after swapping a MAP sensor, o2 sensor, ignition coil, spark plugs, throttle body and IAC cleaning, it was still running like crap, and throwing codes left and right. So it got me thinking about the TPS sensor that i replaced (first code, first part i replaced). I had originally scoured the internet on how to replace the TPS sensor correctly, i asked the people at Auto zone while i was there, i asked my brother who has worked on cars for a long time, my girlfriends brother who is a jeep enthusiast, and a few others about the TPS and if i had installed it correctly. It just kept bugging me that, that was the first code thrown, and it had gotten worse sense i replaced the sensor (hear hoof beats, think horses not zebras).

I searched again, and came across a mustang forum thread about a TPS sensor. In that thread they mentioned that you had to press your foot onto the gas pedal after hooking up the new sensor (with the key on, but car not started), to tell the PCM where full throttle is.......

I went out, and unhooked and rehooked up the TPS, pressed the gass pedal twice and turned the key..............

Car turns on, car idles, car is purring like a kitten. YAY! but ugh i feel stupid now. But lesson learned, and i now have the confidence to do just about anything on the Jeep.

I do appreciate everyone's help, and to anyone that reads this take a lesson, check and recheck your work =)

flash2225 08-26-2013 09:43 PM

And to update again.

I burned through another TPS sensor. Back to the drawing board on this one. Wound up getting an o2 sensor code, and TPS code and battery voltage code. Yay!

The time now is 05:17 AM.

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