1999 astro trouble code P0117

I have a 1999 Chevy Astro with 120,235 miles. My service engine soon light is on. Funny thing is it comes on and off. I took it to Autozone and they tell me its code P0117 = Engine Coolant Sensor Voltage Too Low. I've changed the coolant sensor by the ERG valve and the temperature sensor by the manifold. Then the code was erased but came back on when I turned the engine on. Scan tool stills show same code P0117. I was told it could be a grounding problem. But I have no idea on how to check that. I have no idea now on what to do next to correct this problem. The service engine light recently stayed on and and I might add the van has always idled rough also.

Thanks Qloco.

Ok, I just finished changing cap, rotor, wires, and plugs still no luck . What can I check now?

These conditions must be present for a predetermined amount of time. These conditions must be present for a predetermined amount of time. These conditions must be present for a predetermined amount of time. These conditions must be present for a predetermined amount of time. Predetermined time ranges from 0.5 second with ECT greater than 86°F (30°C) to 2 minutes with ECT -22°F (-30°C). All conditions must be present for at least 3 minutes. DTC P0117 DTC P0117: ECT SENSOR CIRCUIT-HIGH TEMPERATURE (1.9L SATURN) Circuit Description Engine Coolant Temperature (ECT) sensor is a thermistor located in lower coolant passage in cylinder head. ECT sensor resistance is high when coolant temperature is low and resistance drops when coolant temperature increases. PCM provides a 5-volt reference and a ground to ECT sensor. PCM monitors voltage drop on the signal line to determine coolant temperature. ECT sensor is used for fuel/ignition control, hot/cold coolant light, temperature gauge and cooling fan. DTC P0117 will set if ECT reads greater than 284°F (140°C) when engine has been running for more than 10 seconds. DTC will set if these conditions are met after 5 seconds. ECT signal is continuously monitored when ignition is on. Diagnostic Procedures 1. Turn ignition on. Connect scan tool and monitor ECT sensor temperature reading. If scan tool reading is greater than 284°F (140°C), go to next step. If ECT reading is not greater than 284°F (140°C), problem is intermittent. See DIAGNOSTIC AIDS . 2. Disconnect ECT sensor harness connector. If ECT reading is less than -32°F (-35°C), check tightness of harness connector terminals or replace ECT sensor. If ECT reading is not less than -32°F (-35°C), go to next step. 3. Turn ignition off. Disconnect PCM harness connector J2. Remove ECT signal circuit terminal from PCM harness connector. Reconnect PCM. Turn ignition on. If ECT reading is less than -32°F (-35°C), go to next step. If ECT reading is not less than -32°F (-35°C), go to step 5 . 4. Repair ECT sensor signal circuit for a short to ground or short to ECT sensor ground circuit. 5. Replace PCM. Program replacement PCM using required equipment. Diagnostic Aids Use scan tool to review malfunction history diagnostic information. This data can be used to duplicate intermittent problems. Check tightness of harness connector terminals. Start engine and observe ECT reading on scan tool. ECT reading should increase smoothly to about 190°F (88° C) as thermostat opens, and then stabilizes. PCM will turn on cooling fan if an ECT DTC is set. NOTE: For circuit reference, sUsing scan tool, compare ECT and IAT temperature after engine has cooled overnight at ambient temperature. ECT and IAT temperatures should be within 4 degrees of each other with ignition on, engine off

heres some copy paste for you. check for rubbed thru ,burnt wires.