Oldsmobile/Buick Repair: high idle 2001 buick lesabre, engine oil pressure, exhaust gas recirculation

Question
2001 buick lesabre 3.8 ltr. v-6. started intermittent high idle between 1200-2000 rpm while driving then goes back to normal. pulled codes got 1635 twice after erasing once after cleaning IAC. replaced TPS still idles high. code translates 5 volt reference 1 circuit.
what should i check next?

Answer
Hi
The 5v ref signal is probabally causing the fault as one of the sensors that uses it is the MAP sensor.
Here is the list of sensors
The fuel tank pressure (FTP) sensor
The throttle position (TP) sensor
The mass absolute pressure (MAP) sensor
The exhaust gas recirculation (EGR) valve pintle position sensor
The engine oil pressure sensor
The 5v ref ckt. at or between any of these items MAY be at fault.
It would just be a matter of checking the circuit at each sensor for 5v.
I hope this helps.
Good Luck
Pawl