Joe Savoy

terminal C has 5 dc volts
terminal A is the ground and is good
terminal B has 4.7 volts dc but does not change when vacuum is applied i took out the MAP and put it in my 98 GMC and it responds to a voltage drop when vacuum is applied
DTC is 33

Kevin97ss

Can the ground carry a load? Will it light a test light brightly? To check this you must disconnect the pcm connector and run the pcm side to battery ground. Run a test light between the sensor side and battery positive. If the light is bright your wire is good. An ohm meter does not always tell the whole story.

Make sure the pins at the map connector are making good contact and are clean.

Do you have a scan tool that can read the map voltages the pcm is seeing?

Joe Savoy

i have a snap on 2500 g that shows the same voltage as the multi meter a test light shines very bright so i know the ground is good i am still baffled thanks for the help and possibly you have more info hope to hear from you soon pin contacts are good

Kevin97ss

Having a scanner makes the next part easy. You will be checking the pcm. At the map sensor connector short pin A to B. Two things will happen, a DTC for map voltage low and you will see the voltage drop to near zero. If that does not happen short pin B to battery negative and report back. If it does happen move on and do the same thing to pin C. This should do one of two things, it may set a code or it will give you no response with the scan tool. If it does either than the map sensor is bad.

Joe Savoy

bad lead in the black PCM plug repaired and working fine thanks for the advise you are the best thanks again

Kevin97ss

Congrats!

Don't know about THE best, but thank you, and you are welcome.