On my 1998 Max SE stick, I am testing every evap valve, sensor and connection.

I have diagnosed one problem for sure:

Test of the evap pressure sensor with a working multimeter:
-- With key on terminal #3 shows 5 volts as required
-- With key off terminal #1 shows NO GROUND (no continuity)

I need to check the wire and connections involving the black wire that links to Terminal #1 of the evap pressure sensor.

I can't figure out where that black wire terminates -- the last connection it makes -- on its long path to ground.

Hope you can tell me what that last connection is, and where I can find it, so I can start checking each segment for a break, loose connection or the like.

Hope you can help.

 

I know the approximate location. It is by the center pillar on the drivers side. There a 2 wires that are screwed to the car body. They are probably screwed into the floor by the wire harness channel, but they may be inside the pillar.

 

Yes there are ground bundles bolted behind the b piller plastic pieces easy to get to.

 

A ground wire problem can often be dealt with by connecting a ground wire at the device, and the other end at a convenient location on the body or engine block.

 

Still have not solved this problem.

A few days ago I thought about cutting the wire and making a new ground contact near the sensor, but in the wiring diagram I looked at the sensor's ground wire goes through several connections and ultimately that ground circuit ends up at the ECM. I figured there must be a reason why the system doesn't want the sensor to have "pure" ground that bypasses the ECM. Maybe I'm wrong about that.

 

So inside the B pillar I exposed a strong clean grounding location with several black wires clamped by a bolt. I stuck one probe of the multi-meter at that ground and then probed the ground wire that comes into the sensor. There was continuity.

If the sensor ground wire was intended to run to the ECM exclusively, then there would be no continuity from plugging into the shared ground at the B piller... I believe.

So unless someone smarter than I am tells me not to do it, I'm going to run a ground wire from the sensor to the ground location in the B pillar, and hope the sensor works and nothing gets fried.

 

You would have not problems or adverse affects from running a wire like you described. The sensor grounds to the chassis. The fact that the actual point of ground is in the cabin is immaterial. Anywhere on the chassis is the same thing, whether it be the battery negative terminal or any part of the car body.

However, you have made what I feel are 2 contradicting statements. In your original post, you said you did not have continuity from pin 1 to ground. Then in the post above you had continuity from the ground screw in the cabin to the wire in the connector. This cannot be unless the car body is completely broken into 2 pieces. Personally I think your test in the original post wasn't making a good connection with one of the meter leads.