Hellnback

Based on this link, I tried to trouble shoot my XJ
http://troubleshootmyvehicle.com/jee...sensor-tests-1
Test for the presence of power= The reading should be 4.5-5 volts. My reading is .2 volts. his diagnosis is below.


1) an open in the wire between the TP sensor's harness connector and the PCM's harness connector or 2) the PCM may be fried (although a bad PCM is very rare). How do you do this procedure?


Test for Ground=Reading should be 11-12 volts but my reading is 6.85V, his diagnosis is below.


This indicates a problem with either your Jeep's PCM (internal fault/problem) or an open in the wire between the TPS harness connector and the PCM's harness connector. How to do this procedure?


His other test were find so I ruled out bad TPS. Battery ground is .4to .9, my reading is .82,I am find. Position angle at max is 3.5-4.5, my reading is 3.84, I am find.
Hoping for your input Guys.
Thanks,

cliffy

Put your meter on the wire at the end of each of the plugs, it you have anything over say 0.2 in ohms you might have a problem there or try taking a different voltage reading from a different ground point and see if it increases.

CCKen

I don't know what you're after but here's some testing procedures:

The back probe referenced in the procedures can be a safety pin. Make sure it's bottomed out in the connector, next to the wire. Do not pierce the wire.







Procedures:

Hellnback

Thanks CCken. I am trying to test the TPS and based on the test I posted it appears that TPS is ruled out as defective. the advice is check for open wire.


I'll try your procedure this weekend. Again thank you Guys for the input.

Hellnback

Ok Guys, I tested my TPS based on CCKen's recommendation. Please see please see post #3.
Using digital Multimeter
Test no1. on sensor ground network: Off Idle= 0.0 V, Run Idle= .01 to 02 V
Test No2. TPS Signal: Run Idle= .82V, Run WOT= 3.85V
Test No3. 5V supply: Off Idle= .09V, Run Idle= 5.11V


Based on CCKen's post. My off Idle should have read "0"Volts but I did have a reading of .09V. What's next Bros? I appreciate your input.


Hellnback

CCKen

I can't find my notes that I recorded when I made the checklist.


I'll go check tomorrow and see what I see.


To drunk to do it now. tee hee

CCKen

What's next? Nothing, button it up.


I just checked mine and it was .09 volts (12 volt scale).


Also checked CPS and it was .09 volts as well.


When I first developed the check list I didn't bother to check the voltage with the key OFF so I didn't notice.


There must be some keep alive voltage from the PCM in to the 5 volt supply voltage. I pulled the IOD fuse and it didn't change.


Here's the revised version:

Hellnback

Again, thanks CCKen. So based on my OP. I have:

1) an open in the wire between the TP sensor's harness connector and the PCM's harness connector or 2) the PCM may be fried (although a bad PCM is very rare). How do you do this procedure?


Test for Ground=Reading should be 11-12 volts but my reading is 6.85V, his diagnosis is below.

This indicates a problem with either your Jeep's PCM (internal fault/problem) or an open in the wire between the TPS harness connector and the PCM's harness connector. How to do this procedure?
Bro Cliffy can you elaborate a lil bit. what plug are you talking about?
Bro CCKen, How do you do these procedure?

CCKen

.


Edit: What is your root problem anyway?

Hellnback

@CCKen, My root problem was that, I was driving in the freeway and suddenly I felt XJ is not responding to my acceleration until it shut off. so I pulled to the shoulder, tried to start, got good crank but it won't run. after 15 minutes, I started and it ran, so back on the road, runs well for 20min. a mile after exiting the freeway, on a traffic light, it hesitated to move, was able to cross the street then park. after few minutes, I started and it run for about 2 miles then stopped, started and drive again until I reached home. mechanic says, check TPS, that's where I am now. XJ is starting and looks ok, It can go maybe up to 25-30 minutes idling. but tried driving around the block, it stalls. then start again.
Thanks CCKen for your input. Hopefully, other members will learn from this. as I read here in the forum that its common for XJ. some say it may be a ground too. but I ll take one step at a time.

CCKen

Check the fuel pressure at the fuel rail. You can rent a test gauge set up from auto parts stores. Pressure should be 49.2 psi +/- 5 psi at idle. Check again when the engine quits. You'll only get a two second pump when the key is turned to RUN, but the pump should run while cranking the engine. If you don't get fuel pressure while cranking the CPS may be defective.


CPS' do have a bad habit of failing when they get hot.


You can do some preliminary checks of the CPS but it will be hard to do with a thermal failure.

Hellnback

Thanks Guys, will do it later.
Guys, I am back and I was able to check my fuel pump pressure readings. first, switch on/switch off for 3 times, reading was 44Psig, after I started, it went to 48Psig, after I shut off the engine it went to 44Psig after 10 minutes. So I think pump is ok. Watcha think CCken?
I am now looking at Oxygen sensor as next one to be diagnosed. I will replace the S plug cables and of course the plugs too.


So, TPS and fuel pumps are eliminated. maybe PCS. By the way, I noticed too that while testing the pump, after 15 min.the engine appears to be gin "struggle" or gasping for air to continue operating then it shut off, started immediately and is the same, struggling so I revved it up, the engine was able to recover.
Any input guys is appreciated.

Hellnback

I finished replacing the plugs, by the way, the plugs were messed up. sorry guys, I mentioned in my previous post that I have to replace the plug cables too, I was wrong since it has a coil pack, my bad. The result was a smoother engine run, drove around town passed by a drive thru fast food then it stalled. I moved out of the lane then started, drive around it went well for 45 minutes. until its enough for now. will test it again this weekend. I forgot to test the coil.

CCKen

Coil Rail test.


Note that the resistance values are at room temperature. What they are at engine operating temp I have no idea.

CCKen

If the coil rail tests good, I would seriously consider the Crankshaft Position Sensor is suffering thermal failure.


Use only an OEM CPS. Aftermarket CPS' have a habit of failing right out of the box.