islaTurbine

Probably a dumb question but how exactly would one test the voltage of a suspect engine sensor? I’d prefer not to strip any wires to test them. I don’t really see where I can hook my voltmeter up to the DME or its harness. I’m trying to test the voltage of pins III/24 and III/25.

dcdrechsel

very fine sewing needle to pierce wire and alligator clip on test probe to needle .

islaTurbine

I suppose in a similar vein I could make a back probe using a needle or thin copper wire and try to insert it into the wiring connector on the sensor.

theprf

That's what I do, using a stick pin. Copper is not strong enough to push in.

De Jeeper

I will also add....do not probe friont the front of the plug. It will spread the pin and cause intermintant signal. It took months to solve an o2 issue in my swap because the pin was too open due to too large of a probe.

JohnCA58

This is what I use, have many times done troubleshooting where a tech using probes of wrong tools and causing intermittent issues, go thru back side with spoon tools. Caterpiller makes good one also.

islaTurbine

Someone please double check me on this. I think I should be probing AC DC volts in the brown/pink and red/violet wires on the TPS, right? I’ve been doing it with the engine both on and off and I keep getting a reading of 0.0 volts.

theprf

You want DC volts for *everything* on a car except to test wheel speed sensors.

islaTurbine

Yeah I don’t know why I typed AC.

I think I figured out that it’s nearly impossible to back probe the TPS because the backside of the connector has gaskets to make it watertight. I could force the issue to try and get a probe in there but I don’t think it’s wise.

Porschetech3

Yea, pin 2, the center pin,( re/vi) should have 5v on it, pin 1 ( br/pk) is the sensor ground 0v , pin 3 (ye/bk) is the signal wire to DME and should be ~.9v at idle and go up smoothly to ~4.5v at full throttle.....

JohnCA58

That the reason for using spoon tools in back probing waterproof connectors, the spoon wraps around the wiring insulator and goes between the wiring and the gasket to make contact with the metal connector to check with DVOM with no damage to the gasket..

theprf

I have always used a stick pin to slip inside the gasket next to the wire. It's strong enough to not bend when sliding it in.