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Amedee, Jeep Technician
Category: Jeep
Satisfied Customers: 26040
Experience:  ASE certified Technician advanced level specialist. Wisconsin certified emissions state inspector
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1995 jeep grand Cherokee: awhile the check engine light..light comes

Customer Question

my 1995 jeep grand Cherokee will not start fuel pump doesn't get energize when I take the ASD relay the pump works but when i put on it doesn't also pull the codes and only have code 12 present (pcm disconnected from battery) also when i crank it for awhile the check engine light stays flashing like strobe light and some times the security light comes on to do the opening pas anger door thing but still dos not work.
Submitted: 5 years ago.
Category: Jeep
Expert:  Amedee replied 5 years ago.

My name is XXXXX XXXXX I will be assisting you with your vehicle. I have been working on these vehicles for over 10 years so I am very familiar with this system. I plan on helping you get your vehicle back up and running as fast, most efficient and economical way that I possible can. Please listen very carefully and do not make this any harder for me or you than it needs to be. I need your 100% attention and confidence in me as I will point you in the right direction. Please keep in mind, my answers are all based off of information that you provide me with.

Did you say that the security light is on or flashing with the key on?

Does the TPS have 5 volts with the key on?

Does the engine have spark when cranking it over?
Customer: replied 5 years ago.
the security light comes on for awhile only when i crank the engine several times and stays flashing until i shot the key off, also the check engine light comes on at same time and stays flashing very rapidly also all the relays in the engine compartment start clicking and something behind the intake manifold also click for about a minute or so, I do have spark, if i bridge the fuel pump relay it will start and run very rugfh if i take the asd relay the fuel pump does ge energize if i put it back it will no, I will go out and check voltage an the tps.
Expert:  Amedee replied 5 years ago.
Sounds good!

Let me know!
Customer: replied 5 years ago.
tps key on
purple wire 5.0 positive
orange wire 0.7 positive
black wire 0.0 negative. I,m using Power-Pro- and the black was 0.0 but it was pulsing
Expert:  Amedee replied 5 years ago.

And the engine does have nice bright blue strong spark to each cylinder when cranking the engine over correct?
Customer: replied 5 years ago.
yes. is a matter tath i.m not getting the fuel pump to stay on is getting kill for some reason
I'm going to a meeting for one hour so I will go back on line in about one hour
Expert:  Amedee replied 5 years ago.
Ok.. no problem.

You are going to want to check to see if the computer is grounding the pink wire going into the fuel pump relay when cranking the engine over. If so, then check to see if the fuel pump relay has two powers going into the relay with the key on and cranking to activate it.

From what your telling me, I suspect the fuel pump relay is getting grounded by the pcm when cranking. But if not, then we check the security system and inputs to the PCM.
Customer: replied 5 years ago.
I tested the wire going to the fuel pump relay, this my findings
key on
pink 12.3
red 12.3
blue 12.0
orange 0.1 negative

key of
pink 0.0 negative
red 12.6
blue 0.0 negative
orange 0.0 negative

pink 1.0 (the +or - ligth on my power-probe did not ligthup)
red 14.6
blue 14.5
orange 14.5
yes it did run for about 2 minutes and then shut off,it does that some times rigth now it may satrt and sut off again, remember i said tath the check engine ligth some times come on like strobe ligth, whell i notice, when tath happend tath clicking noice comes from wat it seams to be a valve for the EGR system, thisone is on the driver side is cilindrical with two wire coneccion on the top and three vacuum ports , bottom one is pluged and middle one gos to the fron of the car and the top one goes to another valve and from tath valve it tees up goin to the intake manifould and to the EGR valve
Expert:  Amedee replied 5 years ago.

When the engine is not starting, we want to see if the pink wire is getting grounded by the PCM when cranking the engine over.

Let me know!
Customer: replied 5 years ago.
in the no start condition the pink wire is 0.0 negative with the key off but when the key is on it goes to 12.0 positive and stays positive while cranking
Expert:  Amedee replied 5 years ago.
Ok.. then you have a security issue going on here.

Try disabling it by unlocking the front doors manually with the key and even the lift gate in the rear.

Ensure that the CCD bus wires between the modules have 2.5 volts with the key on.

If so and the security system still will not allow the vehicle to start, you might just have a bad alarm module.
Customer: replied 5 years ago.
try the doors with the key but it does the same thing, start run for a minute then shut off again, how do i test the CCD bus wires? I pull the security module from behind the glove compartment, witch wires shul i test and wat values I'm looking for??
Expert:  Amedee replied 5 years ago.
Does this vehicle have an obd2 connector? The BUS wires should go right to the obd2 connector right at the connector under the dash.
Customer: replied 5 years ago.
it does have a OBD1 system the conector is in the engine compartment just behind the ecm wiring harness
Expert:  Amedee replied 5 years ago.
There also should be another connector under the dash on the drivers side to the right of the steering column. It will have 6 pins. The CCD bus wires go into pins 3 and 4.
Customer: replied 5 years ago.
could not find this to the rigth, i did find one to the left coming from the harness it splits into a 6 wire conector two brown wires coming into and two black at the conector the wires ar colored,yellow,white,brown and black
after they conect they go into the harness again and into a plugon the stering column aparently some kind of cable asembly at the other end tthe black one coming in from the switch on the brake pedal
Expert:  Amedee replied 5 years ago.
Then go right to pin 26 and 46 right at the PCM to check the voltage on the CCD bus wires
Customer: replied 5 years ago.
I,m checking the harness rigth? by unpluging the computer, or with the computer plug in?
and if you know the color will be awsome
Expert:  Amedee replied 5 years ago.
The colors will be white/gray and violet/brown. Leave the connector plugged in and back probe these wires to check the voltage. Be sure the key is on.
Customer: replied 5 years ago.
do you have a picture of this conector?? i pull the back of the conector just want make shure igot the rigth one
Expert:  Amedee replied 5 years ago.
I wish I could send one.. but it is against copy write laws to copy and paste any pictures from any manual..
Customer: replied 5 years ago.
with key on the white/gray is at 7.3
the violet/black is 6.0 to 11.0 fluctuating at the same time the valve mention before is clinking then it settles at 11.0 and the clinking stops
with key off booth are 0.0
Expert:  Amedee replied 5 years ago.
Did you check this by back probing these wires using a voltmeter? Did you put the black lead of your meter on battery ground?
Customer: replied 5 years ago.
I use my power-probe
Expert:  Amedee replied 5 years ago.
You might want to check this using a regular voltmeter. If the readings are the same, then you have a bad module on board the vehicle or a wiring issue with the CCD bus wires.
Customer: replied 5 years ago.
using a voltmeter i get 6.7 out the white one and
incoclusive out the violet but if i probe it with the positive cable form the voltmeter to positive on the battery. and black probe to the violet i get 6.8 volts
Expert:  Amedee replied 5 years ago.
According to my references, it should be 2.5 volts with the key on and engine running. It sounds like you could have a bad module on board your vehicle.
Customer: replied 5 years ago.
are talking security module taht is under the glove compartment ?
doest need to be replace?
Expert:  Amedee replied 5 years ago.
ANY module on BUS circuit can affect this voltage. ON this vehicle is would be the security module, ABS module or even the PCM. You might want to disconnect the secuirty module and ABS module and recheck the voltage on these wires with the key on.

I hope this helps! Please don't forget hit the green accept button so that I may get credit for the time that I have spent with you. This is necessary for me to be paid for my work and get credit for assisting you. Your question will not close, and you will still have the opportunity to follow-up if needed. Leaving a bonus and positive feedback is not required, but doing so is certainly appreciated!

I do hope you are as honest with me about your vehicle as I have been with you. If you have any further questions or if you need more assistance, just hit the reply button and we can continue our conversation. Please remember, even if you accept my answer now, you can still repost or respond back to this thread at any time you wish at no further cost and I will be more than happy to continue to work with you until you are happy.

In addition, please allow time between answers as I may be off line spending time with my family or assisting other customers. You can always request me by using the link through my profile page. Just Click on "AMEDEE" next to my picture and I will be sure to respond back in a timely manner.

Thanks in advance!

Best Regards


Customer: replied 5 years ago.
sorry yesterday i had to go school.
according to your last reply, i get tat this is it? now I'm on the same situation when we started, because my vehicle is no different, I was hopping to get this problem pinpoint and get it fix, also you didn't explain any of my findings only direct me to do this testings, i cinceirly hope we can get this problem figure out, so far I don't think my question has an answer. let me know if you can help or if I need different expert.
Expert:  Amedee replied 5 years ago.

Thanks for the reply!

This web site is for informational purposes only. I cannot test these things over the internet. IN addition, you need to either purchase a lab scope or get your hands on one to continue testing. You are trying to hold me to a diagnoses and I cannot even see at your vehicle. I will be happy to answer any more of your questions, but you have to understand we are limited here..