defconOne

Dear members....
just got my cherokee xj 1996 4.0 auto....
my cherokee runs fine....did a marathon for 9 hrs with zero problem...
Now the problem part...he he...
After it rest for 1 night...I hv hard time starting it...
When I turn the ignition switch on....the engine check light is not lighted...
when I crank,the engine will not start...
I will off the ignition switch...switch it on again...crank again(will not start), off again...
One the third time I on the ignition switch....the engine check light will blink very fast for a short time....and will stay lighted...
Only this time when I start...the engine will fire up....

Am I having problem with my ecu? I m new to cherokee and keen to learn..
Been driving a volvo all this while....
I appreciate all inputs....thank you

96tudor

I had a no-start/no-check-engine-light situation just last week. It turned out to be a bad ground to or from the powertrain control module, PCM, (previously referred to as ECU) in the Auto Shut Down, ASD, relay circuit. I also had a relay that was rapidly activating and then deactivating. It cost me $100 to have it diagnosed and $200 to have the ground tracked down and repaired.

It sounds like you have an intermittent connection/communication problem with the PCM. If you don't have a regular service facility that you use, ask friends and coworkers for references. Then call around and ask for diagnostic charges for OBDII systems. My shop charges no more than $97.50 for the computer system diagnostic work. This intermittent problem may leave you stranded sometime, so I'd have it looked at soon.

Usually a blinking check engine light means that catalytic converter damage is imminent. However, I believe that that is not the case in your situation since the engine isn't even running when you get the blinking.

defconOne

96tudor...thank you for the info....will get it checked today....
I hope this ride will be nice to me just like my other tank...he he
Appreciate ur info...still scouting for reliable workshop...
Thank you

96tudor

You're welcome.

davida

I have a 96 & a 97 and both of them have check engine lights that do not come on when there is a trouble code, have you checked for trouble codes?

defconOne

Hi Davida...
no error code...
there is just no check engine lights...
when i turn the key to run...the gen and check engine lights will be lighted just for split seconds and goes off....
still searching for workshop which has the odb reader...
if there is none....guess i will hv to tow this cherokee 200+km to the workshop which has...or just get a pcm in ebay...boo hoo hoo

davida

Most of the auto parts stores will read for free if you don't have a reader.
When you find the problem make sure you post the solution here.

96tudor

Please keep us informed about your progress on this issue, what you try and eventual resolution. My problem wasn't in the PCM but in the wiring harness.

96tudor

I just thought about one thing that you may want to try: cleaning and resecuring the grounds attached to the right side of the engine block by the bolt that secures the engine oil dipstick tube. You may also want to remove the heater control valve to gain better access if you decide to give these grounds a shot.

defconOne

I will do it 2moro....burnt out today...super tired...there goes my weekends...boo hoo hoo...
Will degrease the engine and check the grounding wires...
Thanks for the info....

Gonna sleep now.

defconOne

Checked and found no ground wire....attached one....bad news...still engine check light will go off spilt second after turning on....:-(

Will need a wiring diagram to spot where are the ground wires originally:-)

Noticed that my fuel pump will keep on working even after abs light goes off...normal?

From my observation before this problem...the fuel pump will stop pumping once the check engine lights goes off...correct me if I m wrong.

Now I cannot even get any code....haiz:-(

defconOne

Guys...where is the location of the ecm?It is the metallic box...right?
Do u think it is a gd investment to get the odb reader?
Well...I do not want to go to a mechanic and start telling me stories..
Well...it is gonna take time for me to learn this beauty
Thx guys.

96tudor

The PCM (aka, ECU) is located on the forward end of the front left fender next to the air cleaner. I don't know if an "obd reader" would be much help if you don't have any trouble codes. I think that a list of ground locations may be a better bet. I have to admit that I'm at a loss on this one.

defconOne

Hiya Tudor96,
Thank you...no worries...appreciate ur inputs....
It is a learning process for me....
Will update my findings soon....well...depending if I can find it...

ET JEEP

Have you checked the basics. Are you getting a spark? Does the fuel pump turn on? Are fuses and relays good?

When you turn the key to on, you should have power at the ASD relay and the fuel pump relay. This power goes to the control pin on each relay, usually pin 86. You should also have contant power at pin 30 of each relay.

The PCM provides the ground for these relays. When you crank the engine, the PCM starts reading info from the sensors, cam sensor, crank sensor, etc ready to start. The ASD powers the coil, injectors, altenator and a few sensors. Check your O2 sensor wiring. It tends to get shorted on the exhaust. If this happens you ASD circuit is shorted. You can crank the engine and listen to your injectors with a mechanics stethoscope. You should hear then click if the ASD circuit is good and they are getting power.

You need to check to see what you do have then search for what you do not have. Sometimes cleaning the PCM connector pins and socket helps. Also, ty-wrapping the connector seems to help. This is what some have done with engine starting and running problems. A good PCM ground is also important.