I have a 96 cherokee country with the 4.0 6 cylinder and auto tranny. My ecm number is p56041199. I have a p56041251 from a junk yard. I need to know if this is ok to use in my jeep and if anyone knows what part numbers for ecm will work on my 96 jeep.

 

Being a 96, your going to need a pcm out of a 96, and ideally the numbers need to match, because if you were late model 96, you had some 97+ sensors. Early 96, had 92-96 sensord

 

Thanks for the info. I've been chasing down this problem of when I get to around 3000 rpm the engine surges and looses power. It's like it has no fire for a second and the rpm drops a couple hundred rpm and then it goes back up a couple hundred rpm and does this over and over. Does it in park and driving down the road. Trouble codes for 02 and map sensor. When I changed them and erased codes they came back. The map sensor immediately and the 02 after driving a few miles. I have checked voltage and signal output on map sensor, it's good.
new fuel filter
fuel pressure 50
new map sensor
new tps
new o2 sensors
new cat and muffler
new iac
new air temp sensor
new temp sensor
battery voltage good
no vacumn leaks

 

Part number 56041199 only. '96, 4.0, auto trans, federal emissions.

 

What are the code numbers ?

 

The codes are 14 and 21. Any ideas on what to check next would be greatly appreciated.

 

14 MAP Sensor. MAP sensor voltage too high or low. Check circuit and sensor.

21 Oxygen sensor or circuit. O2 sensor or wiring faulty.

These guy's know way better than me, but I had a thought. Those two may well share the 5V reference feed from the PCM. Maybe meter it at the MAP and go around jiggling wires, even the ones at the rear 02, and see if the reading changes. Just a thought..(theres a hot, 12v wire in the 02 harness, if that were to contact any others, that might jack things up without blowing a fuse)

 

Thanks. Your suggestion of the wires lead me to the problem. The front 02 sensor wires were shorting to each other causing all my problems. Jeep runs great now. So much for the computer and the trouble codes. For me they are just a waste of time. Seems like trouble codes have turned mechanics into parts changers. But I guess we have to start somewhere. Thanks again for a great suggestion.

 

You can send your "thank you" letter to the EPA.

 

Well I'll be dipped! Guess even a stopped clock is right twice a day!

Well done!