code diagnosis

[Wicked_Sludge]

scratch that. i had confused that 34 from the 84 from before.

34 is the EGR position sensor (EVP). its reporting the EGR is further open than should be. chances are here you either have a bad EGR valve or bad EVP sensor. id test it by back-probing the sensor with the ignition on and using a vacuum pump connected directly to the EGR valve to slowly open it. the signal should start low (under 1 volt) and steadily increase with vacuum to around 4 volts.

its possible you got the computer from the wrong year or what-have-you. the knock sensor is a black round thing held to the side of the block with a bolt. it'll have a few wires coming from it. if you dont have one, youve got the wrong PCM.

 

[86jalopy]

will the knock sensor code cause any running problems?


which 2 wires do i probe on the evp?

 

[Wicked_Sludge]

a knock sensor wont cause any drivability problems. its just there to retard timing if it detects detonation.

ground your common probe on your DVOM to the negitive battery terminal and probe all 3 wires on the EVP with the positive probe. one will be ground (0 volts), one will be supply (5 volts) and one will be signal return (under 1 volt with the EGR closed). the signal return is the one you want.

 

[86jalopy]

will do,thanks.

 

[86jalopy]

well i started today by testing the o2 sensor and it's not switchiing and i am not getting 12 volts to the heater.which wire is pos and which is ground?

 

[Wicked_Sludge]

there should be either one or two black wires, those are ground. of the two white wires, one should be 12v+ with the key on and the other should be signal return (between 0 and 1.1 volt). you can ground your DVOM to the negitive battery terminal to test either white wire.

 

[86jalopy]

i got it,the wire coming from the ignition switch was broken.the o2 is switching just fine now.now for the evr sensor.

 

[86jalopy]

no cades for the evr now,so i guess all is well.

thanks for the help.

 

[Wicked_Sludge]

well good deal. maybe fixing that wire from the ignition switch did the truck.

let me know if any more codes pop up and if you get it to pass emissions!