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99 jeep grand Cherokee 4.0. I have a crank no start no communication. I pulled and light tested fuses swapped relays. I replaced PCM with 2 different pcms both identical and flashed to vin. Im not getting 5v to my sensors. No fuel to fuel rail. Pump doesn't turn on. Im absolutely lost. It will try to turn over with starting fluid. I added pic of my dash to show all lights that are on. Any feedback on this nightmare would be greatly appreciated. Thank you in advance.
Dukeh wrote: Im not getting 5v to my sensors. No fuel to fuel rail. Pump doesn't turn on.
Have you check POWERS and GROUNDS at the PCM connectors?
"Knowledge is a weapon. Arm yourself, well, before going to do battle."
"Understanding a question is half an answer." I have learned more by being wrong, than I have by being right.
Check for battery voltage at all the points circled in RED. Start with the fuses.
Make sure there is LESS than 100mv ( 0.1 volt) on the Ground wires circled in BLACK.
"Knowledge is a weapon. Arm yourself, well, before going to do battle."
"Understanding a question is half an answer." I have learned more by being wrong, than I have by being right.
Much appreciated. I will check this out when i get home from work. I wasn't sure how to back probe but think i have figured it. Thank you for the help.
Chad wrote: Check for battery voltage at all the points circled in RED. Start with the fuses.
Make sure there is LESS than 100mv ( 0.1 volt) on the Ground wires circled in BLACK.
Just to be sure it this the cluster i will be back probing?
No. The PCM.
"Knowledge is a weapon. Arm yourself, well, before going to do battle."
"Understanding a question is half an answer." I have learned more by being wrong, than I have by being right.
Just to be sure it this the cluster i will be back probing?
No. The PCM.
Ok. So i leave it plugged into the PCM pull the plastic cover off to expose wires and back probe them that way. I apologize im not the best with the electrical aspect of vehicles.
Ok.... my battery is dying i got a 9.76 reading off of it i need to recharge. On A2 back probe my reading was 9.68 on back probe of A22 my reading was .009. On back probe of A31 reading was .006. There was no fuse 22 15A in my relay box and fuse 11 20A was a reading of 9.68 it was my rear defroster. I added pics of fuse box and relay box for reference. Thanks again guys the help is greatly appreciated.
You really want to make sure you have a good battery that's charged before doing any electrical testing. I hate to tell you to charge it and do it again, but you do. Low battery voltage causes all sorts of weird things to happen and you need a good baseline for your tests. 9v is very low. Even 12.0v is discharged.
Dukeh wrote: There was no fuse 22 15A in my relay box and fuse 11 20A was a reading of 9.68 it was my rear defroster.
Hmm.
It looks like we have some discrepancies. Do the wire colors for A2 and A22 match the diagram? (EDIT: Do all wire colors match the diagram?)
Can you post the Vin #?
"Knowledge is a weapon. Arm yourself, well, before going to do battle."
"Understanding a question is half an answer." I have learned more by being wrong, than I have by being right.
Tutti57 wrote: You really want to make sure you have a good battery that's charged before doing any electrical testing. I hate to tell you to charge it and do it again, but you do. Low battery voltage causes all sorts of weird things to happen and you need a good baseline for your tests. 9v is very low. Even 12.0v is discharged.
Nissan Technician
Thank you. I will recharge it tomorrow. Battery was just bought in July so shouldn't have a problem taking a charge.
The connector you have pictured is connector #3, or "C". We want connector #1, or "A".
The color sequence should match this:
As for the fuses, it looks like there are two different fuse boxes. Look around for another one.
"Knowledge is a weapon. Arm yourself, well, before going to do battle."
"Understanding a question is half an answer." I have learned more by being wrong, than I have by being right.
Monde wrote: Have you checked the relay circuits? Pin 30 should have battery voltage VT/WT, Pin 85 battery voltage R/DB 86 Fuel pump control relay BR (Test light to ground and tip on pin 86, check for control with key on engine off or cranking. Test light should light.
Also, you may start unplugging sensors( no thermistors) to see if you can get the 5v reference back. Does your security light go out when you crank the vehicle?
I did test light my relays and the bulb did light up. Ill double check tonight when i get home. Yes security light stays on when cranking. Ill try pulling sensors again as well i tried that but may have did it wrong.
Chad wrote: The connector you have pictured is connector #3, or "C". We want connector #1, or "A".
The color sequence should match this:
As for the fuses, it looks like there are two different fuse boxes. Look around for another one.
Ok sorry about that i will check the right one out tonight and relay the information. There is a smaller fuse box underneath the dash ill see if thats the one as well.
So i back probed the correct cluster i believe. A2 12.53 a22 12.69 a31 .007 a32 .007. I recharged my battery it 12.7. I checked pin 85 fuel pump relay it was 12.54. Light test pin 86 no light.
Dukeh wrote: So i back probed the correct cluster i believe. A2 12.53 a22 12.69 a31 .007 a32 .007. I recharged my battery it 12.7. I checked pin 85 fuel pump relay it was 12.54. Light test pin 86 no light.
