speed/ref sensor plug = 5 wires ???

[JacRyann]

I picked up a used 951-in-a-box about a year ago and put it all back together. I've been troubleshooting a random no-start condition. When this occurs, I wiggle the connectors for the speed/ref sensor and it starts right up every time. Figured there's a corroded or loose-wire. I've replaced both harness connectors with new ones and they have proper continuity to the DME.

While doing that, I noticed that one of the plugs on the sensor-side had been replaced, so I pulled off the rubber-boot and found this:



I can match up the shielding-braid, signal and ground-wires to the wiring-diagram and they go to the DME properly. Basic resistance checks on sensors is OK according to procedure on Clark's Garage. Oscilliscope waveforms are over minimum height with no noise, so I think it's this sensor plug that's been replaced. Some questions:

1. What are the two additional smaller wires on the side?
2. Should they be connected to something?
3. Should I clip and wrap the ends? They have wire showing and I suspect they may be shorting against the braid, which may be why I'm getting random no-starts until I wiggle that connector.

Thanks.

[kfray]

It appears this shielded 4 conductor cable replaced the original 2 conductor shielded cable which connects to the sensor. The 2 extra wires are not required and should be taped off. Make sure that the wires going to pins 1 & 2 a solid connections. Also make sure that there are no breaks or nicks in the insulation on the wires in pin 1 & 2 that the shield strands might be touching.
I do not know why there would be a 4 conductor shielded cable to the sensor, seems as this is some type of hack, it may be best to replace the sensor.

[JacRyann]

The cable is the original factory wire that goes to the sensor. The other end goes into the plastic part on the sensor just like the other one. Although this cable is about 2" shorter due to plug-replacement.

I checked continuity of those two wires and they don't connect to each other or any of the other wires. Perhaps they're connected to the metal-sleeve of the sensor? Didn't check that as I didn't want to pull out the sensor to test.

Anyway, I've clipped off the exposed ends of those two little wires and taped them up. Also poured silicone into rubber-boot before sliding it back on similar to the harness-side connectors. Hopefully that'll remove the stress-riser where the wires go into the plug. So far, it appears to be working, started up on the 1st crank. But the random no-starts were truly random, sometimes shows up once per day, sometimes once a week.

Thanks for the help!

[guru944]

Those 2 extra wires are not OEM however if they are not connected to anything, i would recommend also grounding them to the shield. That will prevent them from floating (noise) or building up DC charges like a capacitor and corrupting the timing signals from the sensor(s).
Later...