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Hello:
Joined this forum because I saw other folks discussing TPS issues on the Quadrajet. The rig I’m working on is an 89 Chevy Caprice with the 305 engine. The code reader is reading 21: TPS voltage to high and 45: rich exhaust (makes sense)
I have been consistently reading about 3.39 volts (on the middle connection that should read the voltage variation) no matter what position the throttle is in. I replaced the TPS and also the ICM (as it is called on the 305 olds engine) and the reading is the same, with a very small variation when the throttle is operated.
I then unplugged from the TPS and checked the voltage coming from the plug, the 5 volts is coming to the top wire, and BEHOLD the middle wire (that should cary the varying voltage) is reading 3.39 volts when disconnected. Shouldn’t this read 0 or close when the TPS is disconnected? I suspect this is over-riding anything the TPS is trying to send.
When I first checked this is when I replaced the ICM. Still the same. I don’t have any visible shorts and suspect some type of Voltage Leak which is why I replaced the ICM, AC Delco parts. Any ideas?
Thanx much..
 
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