2000 Century OPEN2 Fuel Mode

[jwichman]

Intermittantly, my 2000 Century switches to OPEN2 Fuel mode. Typically it is at highway speed and under load while climbing hills, almost all power engine power is lost. Occasionally, a trouble code, is set P0101 but not always. If I stop and shut the engione off for 10-15sec the fuel system resets and the car starts and runs fine for the remainder of my trip.
Code P0101 is MAF or VAF A Circuit range/performance. I have checked the MAF sensor and wiring harness.

Any suggestions?

Thanks,

[BNaylor]

How did you check the output of the MAF sensor? Basically you can check the 5 volt PCM reference voltage at the input wire of the electrical connector but as far as checking sensor range/performance at the output you need an oscilloscope because the PCM looks for a frequency range based on what it senses at the MAF wire element. You may have a bad MAF sensor based on the DTC or an obstruction in the intake system.

[jwichman]

Originally Posted by bnaylor

How did you check the output of the MAF sensor? Basically you can check the 5 volt PCM reference voltage at the input wire of the electrical connector but as far as checking sensor range/performance at the output you need an oscilloscope because the PCM looks for a frequency range based on what it senses at the MAF wire element. You may have a bad MAF sensor based on the DTC or an obstruction in the intake system.

I have had the MAF sensor out for a visual check and checked the intake for obstruction.
I have a scan tool that will monitor the MAF sensor as I am driving. The value displayed for the MAF seem reasonable. It usually runs less than 1.0 at idle up to 2.5 while crusing and upper 3 and lower 4 when accelerating or climbing hills. The more throttle I give it the more MAF.
If I understand it correctly, the PCM reads the actual MAF value and also calculates a predicted MAF value based on TPS, MAP, IAT, rpm and etc. If the predicted value does not match the actual value or within a given % a code is set. If so, it could be the predicted value that is incorrect because of a fault in one of the other sensors used in the calculation???

[BNaylor]

I guess it is possible but if the other sensors were acting up it should throw a related DTC. In my experiences MAF sensor DTCs like P0101, P0102 and P0103 are typically the MAF sensor. The problem with the voltage readout on an odb-ii scan tool is it does not look at the frequency of the signal. Voltage seen can appear to be correct. The MAF puts out a frequency range of 1500 Hhz to 10500 Hz and that is what the PCM module looks at. To generate the P0101 DTC there is an error between the actual airflow and calculated airflow.