Ok I have a 99 jeep Cherokee sport 4.0 I havent been able to get it to start in almost a month. Have been trying almost every thing
1. Changed ignition coil
2. Changed plugs and wires
3. Changed battery and starter
4. Changed fuel pump
5. Checked injectors
6. Changed distrib cap and rotor
7. Replaced timing components
8. Changed CPS
None of this worked, i pulled the following codes from it but I am at a loss please help.
1. P0751 overdrive pressed low
2. P0700 transaxel control sys fault
3. P1687 no MIC Bus
4. P1698 ECM fault no CCD message TCM
5. P1694 no CCD message received from ECM
6. P0122 PTS low circuit

 

It's time for some basic testing.

1. First off is testing for spark. Take out a spark plug, keep it attached to the plug wire. Place the plug electrode near a good engine ground. Have a buddy crank the engine over while you watch. You are looking for a strong, BLUE, snapping spark.

2. If you have spark (and only if) then check fuel pressure. Must be done with a gauge. For a 99, the spec is 49 psi, plus or minus 5 psi.

3. If spark and fuel check out okay, then you need to know if you are getting a "pulse" from the computer to fire the injectors. Can test for that with a "noid light" installed inline to the injector.

With the codes you are showing, it is possible that you have a computer (PCM) issue or wiring related to it. But replacing a computer is a "diagnosis of exclusion" and I only replace it when everything else has been ruled out.

Time for some basic testing as I outlined above to help guide the way. Good luck and keep us posted on what you find!

 

It can be frustrating but it may be time to go back to basics. You need fuel, air and spark. There are ways to check for those. Do it. Also, P0122 is the throttle position sensor code. Check the wiring and plug to that. For that matter check ALL your wiring and connectors. And grounds. Any ground you find, unbolt it, clean it, and bolt it back up (even if it looks clean already). Good luck!

 

I checked the spark its strong. I checked the pressure its 48psi and I checked the pulse and its fine so now what

 

by the sounds of it i would be checking grounds then head towards the pcm pull it out check the board for burnt spots

 

It ran fine before and mysteriously stopped, something happened that caused it to stop or its never run?

 

I agree with this strategy. I would not just look at grounds though, I would "freshen" them. Disassemble, clean until shiny, reassemble.

There is one sensor that I would test here as well. It is the "camshaft position sensor" located in the distributor. If this has gone south, you can have good spark and fuel and all, but have a no start.

 

If this is accurate, then the IAC (Idle Air Controller) in the throttle body is the next item to check. It can be tested by attempting to start while feathering the gas pedal slightly to let a little bit of air through the throttle body. If the vehicle tries to start when doing this, it is an indication that the IAC is not allowing air through the throttle body, when the foot is off the pedal during start up.

After that simple test. The next test would be a compression test.