how do i tell if my pressure sensor is working or not?

second, where is the o2 sensor on the wiring harness for a 88 t2? i can seem to be able to find it. its is cut by the previous owner behind where the connectors are. cant seem to find a loose black wire anywhere to hook it up. does it suppose to go all the way to the other side of the engine bay?

third, under the tmic, where the tps and the sensor in the elbow, both connect into the harness, there's a black wire thats loose/cut, it doesnt seem to be connected to the eblow sensor or the tps. there's also a black wire with a connector right next to it and also cutted. the connector is clipped onto the tmic bottom bracket, does the two loose wires go together?

eric.

 

The o2 is in the exhaust passanger side the wire for that sensor is in the harness behind the filer neck on the top right side of the engine.The two black wires do not go together,One is for the o2 and the other I believe is for a sensor on the bac

 

setting the tps is used with the multimeter, its told to make sure to unplug the tps from the harness and set the key to on, what would happen if u didnt unplugg the tps form the harness and stuck the multimeter into tbe back of the plug? would it mess up anything?

eric.

 

Put a voltmeter on the brown/red wire. With the ignition ON and the engine not running the voltage should be ~2.5V. Start the engine and let it idle, and the voltage should drop to ~1.2V. Revving the engine should make the reading change. If you get no reading or funny numbers you should replace the sensor. If you get a 2.5V reading that doesn't change with the engine running, the pressure sensor vac line is leaking or disconnected.

It comes out of the loom at the same place at the wire for the BAC valve. It's the yellowish plug in this pic.

That should go to the knock sensor, which is on the engine centre plate at the base of the oil filler pipe.

 

that yellowish plug in the picture, i dont have it on that side of the engine, i have it on the other side where the tps and air thermosensor is. is that the o2 sensor wire? its also yellowish connector thats is clipped onto the bottom of the tmic bracket.

eric.

 

thats the one that is cut wat is that suppose to be connected to? do i need it?, i cant seem to find the o2 sensor wire in the harness on the passenger side.

 

its not cut where the you can see teh black wire, but th eother side, the side thats pointing towards the passenger side, its been cut there.

eric.

 

Eric I'll snap some pix for you when I get home from work.

 

No, that's the knock sensor wire which has the same type of connector.

That photo was just to show you where to look for your cut wire.

 

wat does the konck sensor do? do i need it? where do it is connect to? i followed it and it goes somewhere near the oil filler, but where does the other end to go?

eric

 

The knock sensor is used by the ECU to detect knocking/detonation/pre-ignition. If the ECU detects knocking it retards the timing to stop it. Being old technology, the FC's knock detection system isn't very effective over ~4000rpm, as the engine becomes to noisy. It's mainly there to avoid knocking caused by low-rpm lugging.

You don't need it for the engine to run, but it's a little extra insurance for free. All you have to do is connect it up. The knock sensor's wire comes out of the loom at the same place as the TPS and intake temp sensor wires.

 

that answers my third question on my first post. thanks for helping. now i need to look for the o2 sensor wire.

eric.