CoachT

2004 grand Cherokee Laredo 4.7l. 120,000 miles. Runs rough when at operating temperature. ASD relay clicks constantly causing voltage to bounce up and down to fuses 16 injectors and fuse 26, heating fan solenoid and O2 sensors. Constant and ignition voltage to ASD relay are constant and Good. Unplug the fan solenoid, no change. Pull the fuse feeding fan and o2 sensors, no change. BUT, when I jumper voltage from an unaffected fuse and apply it to the top of fuse 26 for fan and o2 sensors, the problem disappears. Tried to hand over hand and continuity test every feed and ground from the fan solenoid back through the fuse box. Cleaned all the grounds underneath for the o2 and inspected wires. No apparent damage. Any ideas?

Cherryokee

Usually, the most active/noisy relay is the PURGE system. If ASD is triggered then I'm surprised your Jeep keeps running, rough or otherwise.

Is CEL illuminated? Sometimes intermittently occurring codes can get stored without lighting the CEL. Have you scanned it yet? Are there any stored codes? Write them down and tell the forum - you'll get more help.

Afterwards, whether or not you found and recorded codes - the following is a benign action that could reap great rewards:
Obtain electrical contact cleaner spray. Carefully - Disconnect battery negative only and then unplug ECM connectors, inspect, clean/spray and air-dry all unplugged connectors, inspect and gently/firmly reconnect ECM, followed by restoring battery negative.

CoachT

There are no stored codes. The only different codes it ever showed was purge valve, codes and oxygen sensor heater codes as I was unplugging them while the jeep was running. Once I plugged them all back in those codes went away.
There were no codes when I started the Jeep today, but when the vehicle got to operating temperature, the problem started happening.
It posted three codes:
1. P0136 O2 sensor, bank one, sensor 2. (which I replaced about a month ago.)
2. P1499 hydraulic fan solenoid ckt.
3. A. P1495 LDP solenoid ckt (replaced a month ago and did rudimentary vacuum test on every vacuum line I could find and especially at the elbows).
B. Left front seat belt switch short circuited to battery or open. (Pulled breaker for front seat and no change)

I would assume the first two codes could be caused by the voltage to their shared fuse, bouncing up and down? It wobbles by 3-4 volts, but again, the voltage coming in to the ASD is solid 13.4 when running.

thank you for any help!!!

Cherryokee

Unplugging sensors while the car is running may bring bad mojo for the ECU. Depending on the "health" of the unit and connections (including hard chassis-grounds) the practice can blow the ECU input for the sensor under test. Best practice is to excite the questionable sensor output with a ~1K ohm resistor, connected either to ground (pull-down) or to 5 volts (pull-up).

When replacing sensors did you go with aftermarket or Mopar parts? Some think it's a myth but I'm living proof that using OEM for sensors really does matter. Regardless, it seems that "fluctuating voltages" might be pointing at the need for ground-point connection improvements, so get your factory manual, a wire brush and some dielectric grease then get busy. And definitely revisit the last items you reworked (this, assuming the worst troubles followed the last services).