P0122 Throttle Position Sensor Low InputOriginally Posted by BillBoost37
P0452 Evaporative Emission Control Pressure Sensor Low Input
P1635 5 Volt Reference 1 Circuit
From what I have read, and have been able to tell from a circuit diagram in my Haynes manual, there is most likely something dragging down the excitation voltage (the 5V Reference 1 circuit that supplies the TPS and the fuel tank pressure sensor, and most likely the fuel tank level sensor). Other postings around the internet show that the fuel tank loss of indication usually shows up along with these codes. One apparent common fault is breakdown of the 5V reference signal wiring insulation that can short it or otherwise drag it down. Going to try to track this down when the weather cooperates. In the mean time, car seems to run OK, once I clear the codes out after starting the car, they don't come back again until the next restart. There is indeed a certain amount of bogging on acceleration where the car probably should downshift but doesn't, it does accel OK if I manually force a manual downshift with the shift lever. I hope that the problem is a fault in the supply circuit within the engine management system module, if it is, I will likely build a small external supply ( temporarily, for troubleshooting purposed it could be as simple as 3 D cell batteries in series) if I cant find any faults external to the module in the wiring or the sensors themselves. One common thread that I see in the discussion of problems like this is that most people, professional repair shops included, immediately respond to a code from a specific component like a TPS by replacing it. In my experience as an electrical engineer and before that, as a bench rat in a TV and radio repair shop as a teenager, is that is far more common to have problems with simple things like bad wring or bad ground connections. BTW, the intermittent low windshield washer fluid light was indeed valid, it took nearly a whole gallon to fill it. I filled it a while back, and am surprised it was down so low, maybe there is a slow tank leak I am not seeing.
