trouble with trouble codes 1989 trakker
 

Issue with o2 sensor and map sensor, when disconnected no fault codes are flashed, the sensors are working as they effect the engine running condition. o2 sensor output OK.
If I disconnect tps or water temp or air temp sensors the codes will appear. Just wonder if there is a fault within the ecm not detecting a disconnect.

My MAP DTC won't set due to low voltage unless the throttle is held open past 5°.

https://cimg1.ibsrv.net/gimg/chevrol...fabb4078b2.jpg