P1128-CLOSED LOOP FUELING NOT ACHIEVED - BANK 1
P1129-CLOSED LOOP FUELING NOT ACHIEVED - BANK 2
In closed loop fueling, the computer takes readings from the oxygen sensors which read +/- of 14.64 AFR (Stoich) and makes corrections for it. If your car is idling @ 13.5 AFR, the 02s can see this, and will know to pull out enough fuel to get back to stoich.In open loop, the fueling is purely based off the MAF transfer function and the open loop fuel table. This table has to be calibrated any time you make MAF changes, and changes that affect the airflow of the MAF.When a car is started, the computer is in open loop until certain criteria is met - ECT sensor reading, O2 sensors heating up,MAP/MAF sensor readings.
Because it both banks are staying in open loop condition, either the ect sensor is not giving a correct reading or thermostat is sticking open and not allowing coolant to reach operating temperatures, fuel pressure is incorrect due to weak pump or clogged filter, O2 heaters not functioning properly, PCM faulty, or even base engine fault such as incorrect engine timing.
To walk you thru all the testing needed to determine which is at fault, you will need a scan tool with live data capability and testing functions, a voltmeter, a fuel pressure tester with gage, infra-red temperature gun, and cylinder compression tester.
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