PO121 : TP Sensor Performance = The PCM supplies 5V to the TP sensor(throttle position). The TP sensor is a variable resistor that drops the voltage to about 4 volts at WOT(wide open throttle) to less than 1 volt at closed throttle. Some TP sensors are adjustable. others have a learn procedure to determine closed throttle. PO171 Fuel Trim System Lean = In closed loop the PCM adjusts fuel delivery based on H2OS 1 readings and is indicated by long & short fuel trim values. If lean the PCM will add fuel (fuel trim above 0%) & if rich the PCM will reduce fuel(fuel trim below 0%) PO128 ECT Below Thermostat Regulating Temperature = possible failed thermostat, low or empty on coolant, Engine Coolant Temp Sensor, Poor connection/Harness/Wires, faulty PCM Connection. I think you hit the nail on the head , the ECT Sensor ( which is different than the temp sensor for the dash gauge)
562 views
Usually answered in minutes!
×