Ok XJ pros, I need your help here. I have done my due diligence and researched as much as I can and tried everything I know to fix this problem but it has not been resolved.
Background: 2000 Jeep Cherokee Classic, 4.0l, Automatic, 165,000 miles (Does not have the chip keys, immobilizer system. My keys are black and they are original)
A few days ago I tried to be the good neighbor and help my neighbor across the street fix his tandem axel trailer that had a pigtail pull loose after he went around a turn due to not enough slack. His 7 pin trailer plug on his 4runner wasn’t working so I told him I had one on my Cherokee we could try. ( I installed this years ago. Hooked up everything but the aux brake line) He was in the back with the pigtail plugged up and I went up and turned the lights on. When I got to the back I saw he was holding one of the trailer wires and jumping from blade to blade on the open pig tail. Wouldn’t you know it a spark and my drivers side tail light went out. I didn’t know he was doing this, I would have been using my meter! We blew a fuse right? Yes, so the 10 amp fuse on the passenger side kick panel #7 I believe was blown. Replaced it. Lights worked. Fixed the trailer. Go to move the Jeep. Cranks but no start!!!
Start investigating. No gauges. 20 seconds after the key is turned to run, “NO BUS” and the engine light is on. Everything else works, lights, blinkers, radio, blower etc. Start checking more fuses. Inside kick panel and PDC. No other fuses blown. Wiggle the shifter, put it in neutral.(will not crank in D or in gear so I feel NSS is working) Still nothing. OBD2 Scanner will not connect. Acts like no fuel. Fuel pump is not coming on. No fuel pressure at Schrader valve. Got online read tons of articles. (here and other places) unplugged the CPS like suggested as well as other sensors, and still no gauges and NO Bus is still there. Left battery disconnected for half an hour. Pulled instrument cluster out and examined. Cleaned contacts etc. Re-seated and insured positive connection. Cleaned, steel brushed and reseated all ground contacts while waiting No go. Tested the CPS. It showed low resistance so that tells me it is bad. Ran to Advance Auto and picked up a Crank Position Sensor (sorry, dealership is no where near me and it was late) $97 later got it installed. NOPE! Disconnected main wire harness at drivers side kick plate. Electric contact cleaner, dielectric grease… Still the same problem, so I started at the ECM, disconnected, cleaned contacts, dielectric grease. Recheck. Still down. Pulled ECM schematic and checked incoming and outgoing values. 12V present from bat, 12v present from ignition, 5V output present to sensors. (actually is 6V)
Here is where I start to see an issue. Tested voltage at the sensors themselves. Mass Air Flow sensor only showing 3V, one of the 02 sensors only shows 4V. Unplugged Cam Shaft Position Sensor. Still not working.
So I have something bleeding the voltage. I disconnected every sensor I could find or knew of. Still same problem. Went to the PDC and looked at the relays. Fuel pump relay is not coming on. Swapped that out with another one. Didn’t make a difference. Checked voltage at the relay socket. 12V is there from the power side but no 12V signal to energize the coil. Did the same test on the ASD relay. It happens to be the same relay as the horn relay inside the passenger side kick panel fuse area by the way. It has 12v power as well but no 12V signal to energize the coil. So that explains why the fuel pump is not running. But why no signal from the ignition. The ECM has signal from the ignition. Inline ignition switch fuse is good.
I cannot find a wiring schematic telling me where the wires go when they leave the ignition switch. I think if I can find the sensor that is bleeding the power on the 5V side I can get the no bus to go away but what about the ignition switch power to the ASD relay???
I am at a real loss and feel like I have exhausted most options. I haven’t changed the ECM because I don’t think that is the problem. It is functioning with exception of the lack of communication and “NO BUS”
Can anyone help me with proper wire diagrams or with something I may be missing?
I really appreciate any thoughts or ideas. I know this “NO BUS” issue has been gone through many time and 90% it is the Crank Position Sensor. But my new one meters out correctly and with it unplugged it doesn’t change anything. I feel I have hit every sensor I know but the problem could be in a line going to the sensor itself.
I think the foul up by my neighbor contributed but then again it could just be coincidental.
Any thoughts or suggestions or help would be greatly appreciated. Thanks
Background: 2000 Jeep Cherokee Classic, 4.0l, Automatic, 165,000 miles (Does not have the chip keys, immobilizer system. My keys are black and they are original)
A few days ago I tried to be the good neighbor and help my neighbor across the street fix his tandem axel trailer that had a pigtail pull loose after he went around a turn due to not enough slack. His 7 pin trailer plug on his 4runner wasn’t working so I told him I had one on my Cherokee we could try. ( I installed this years ago. Hooked up everything but the aux brake line) He was in the back with the pigtail plugged up and I went up and turned the lights on. When I got to the back I saw he was holding one of the trailer wires and jumping from blade to blade on the open pig tail. Wouldn’t you know it a spark and my drivers side tail light went out. I didn’t know he was doing this, I would have been using my meter! We blew a fuse right? Yes, so the 10 amp fuse on the passenger side kick panel #7 I believe was blown. Replaced it. Lights worked. Fixed the trailer. Go to move the Jeep. Cranks but no start!!!
Start investigating. No gauges. 20 seconds after the key is turned to run, “NO BUS” and the engine light is on. Everything else works, lights, blinkers, radio, blower etc. Start checking more fuses. Inside kick panel and PDC. No other fuses blown. Wiggle the shifter, put it in neutral.(will not crank in D or in gear so I feel NSS is working) Still nothing. OBD2 Scanner will not connect. Acts like no fuel. Fuel pump is not coming on. No fuel pressure at Schrader valve. Got online read tons of articles. (here and other places) unplugged the CPS like suggested as well as other sensors, and still no gauges and NO Bus is still there. Left battery disconnected for half an hour. Pulled instrument cluster out and examined. Cleaned contacts etc. Re-seated and insured positive connection. Cleaned, steel brushed and reseated all ground contacts while waiting No go. Tested the CPS. It showed low resistance so that tells me it is bad. Ran to Advance Auto and picked up a Crank Position Sensor (sorry, dealership is no where near me and it was late) $97 later got it installed. NOPE! Disconnected main wire harness at drivers side kick plate. Electric contact cleaner, dielectric grease… Still the same problem, so I started at the ECM, disconnected, cleaned contacts, dielectric grease. Recheck. Still down. Pulled ECM schematic and checked incoming and outgoing values. 12V present from bat, 12v present from ignition, 5V output present to sensors. (actually is 6V)
Here is where I start to see an issue. Tested voltage at the sensors themselves. Mass Air Flow sensor only showing 3V, one of the 02 sensors only shows 4V. Unplugged Cam Shaft Position Sensor. Still not working.
So I have something bleeding the voltage. I disconnected every sensor I could find or knew of. Still same problem. Went to the PDC and looked at the relays. Fuel pump relay is not coming on. Swapped that out with another one. Didn’t make a difference. Checked voltage at the relay socket. 12V is there from the power side but no 12V signal to energize the coil. Did the same test on the ASD relay. It happens to be the same relay as the horn relay inside the passenger side kick panel fuse area by the way. It has 12v power as well but no 12V signal to energize the coil. So that explains why the fuel pump is not running. But why no signal from the ignition. The ECM has signal from the ignition. Inline ignition switch fuse is good.
I cannot find a wiring schematic telling me where the wires go when they leave the ignition switch. I think if I can find the sensor that is bleeding the power on the 5V side I can get the no bus to go away but what about the ignition switch power to the ASD relay???
I am at a real loss and feel like I have exhausted most options. I haven’t changed the ECM because I don’t think that is the problem. It is functioning with exception of the lack of communication and “NO BUS”
Can anyone help me with proper wire diagrams or with something I may be missing?
I really appreciate any thoughts or ideas. I know this “NO BUS” issue has been gone through many time and 90% it is the Crank Position Sensor. But my new one meters out correctly and with it unplugged it doesn’t change anything. I feel I have hit every sensor I know but the problem could be in a line going to the sensor itself.
I think the foul up by my neighbor contributed but then again it could just be coincidental.
Any thoughts or suggestions or help would be greatly appreciated. Thanks