was working fine with no problems. went to the store, came out and crank no start. had fuel but no spark so i changed the crank sensor, cap and rotor and coil. still no start so i had it towed home. then checking the power to the ecu i found i had none but checked the fuses that feed it and they both have power. not sure where to go from here
97 xj crank no start no power to ecu but fuse 11 at block is good and fuse 21 in pdc is good
- Thread starter XJFILX2
- Start date
- Location
- Minneapolis, MN
Does the fuel pump run and prime for 3-5 seconds when you attempt to start?
Test the CPS. Cheap crappy Chinesium engine sensors are often out of specification or even failed right out of the box.
When the ignition key is first turned ON, 12 volts travels from the ignition switch to the ASD relay. The PCM provides ground to the ASD relay to energize it. The ASD relay sends the 12 volts to the primary side of the coil. If after a few seconds no signal is detected from the faulty CPS, the PCM opens the ASD relay and 12 volts power to the coil and fuel pump is removed.
Inspect and test the wire harnesses under the hood. Look for chafed or melted wire insulation and other harness damage, especially near hot exaust and sharp sheet metal the valve cover. Inpsect wire plugs for corrosion and bent or pushed back wire plug pins.
Test the CPS. Cheap crappy Chinesium engine sensors are often out of specification or even failed right out of the box.
When the ignition key is first turned ON, 12 volts travels from the ignition switch to the ASD relay. The PCM provides ground to the ASD relay to energize it. The ASD relay sends the 12 volts to the primary side of the coil. If after a few seconds no signal is detected from the faulty CPS, the PCM opens the ASD relay and 12 volts power to the coil and fuel pump is removed.
Inspect and test the wire harnesses under the hood. Look for chafed or melted wire insulation and other harness damage, especially near hot exaust and sharp sheet metal the valve cover. Inpsect wire plugs for corrosion and bent or pushed back wire plug pins.
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the fuel pump does not get a signal from the from the ECU so its not priming but when i jump the relay it does work.
The CPS i just put in a new one thinking that was the problem and its an OME not a cheep one.
The ASD is not energizing, it has 5v on it not 12v. dont know why
my biggest probolem is i have no power to the ECU and I checked all wires and for melted and cant find any
Apparently I'm causing myself more problems as I move along. I found a ground wire off at the coil, somehow i missed that when i put the new one on and the main plug on the wire harness behind the distributor was loose, I fixed both of thoes and now have power to the pins 2 and 22 of the A connector of the ECU. but still have no communication to the ECU from the scan tool and still have crank no start. Any more Ideas on this? is my ECU dead?
- Location
- Minneapolis, MN
No communication with ECU is commonly a short circuit. Either an OBD-II 5 volts CCD Bus circuit is shorted, or 12 positive volts is shorted to the CCD.
Bus. Improperly secured wire harnesses rubbing on the block or valve cover, and failed factory wire splices, or Bubba repairs are good suspects. Don't forget to look at the O2 sensor wire harness and wire plug for damage.
Test the individual OBD sensors looking for their 5 volt supply and for continuity to ground and continuity to the ECU. If you find 12 on the CCD Bus you are getting closer. Common 12 positive short circuits are failed wires in the drivers door and tailgate, and the horn circuit shorting to the TPS ground thru a fault in the air bag. Unplug the horn relay to see if there is any change.
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Bus. Improperly secured wire harnesses rubbing on the block or valve cover, and failed factory wire splices, or Bubba repairs are good suspects. Don't forget to look at the O2 sensor wire harness and wire plug for damage.
Test the individual OBD sensors looking for their 5 volt supply and for continuity to ground and continuity to the ECU. If you find 12 on the CCD Bus you are getting closer. Common 12 positive short circuits are failed wires in the drivers door and tailgate, and the horn circuit shorting to the TPS ground thru a fault in the air bag. Unplug the horn relay to see if there is any change.
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