Smitty454

Hi all,

Im trying to test the continuity on the main electrical connector on my 4l80e. I recently swapped internal and external wiring harnesses and now im getting a P0758 and im trying to narrow it down before I drop the pan. Im thinking my soldering job could be bad since the transmission shifted fine before.

I tried testing the continuity by disconnecting the connector and then probing the pins but I could not get a continuity beep on my multimeter on any of the wires.

Is there a better way to do this?

Thanks for the help.

ss.slp.ls1

iTrader: (36)

I test each and every wire for continuity when I build a custom harness. With your multimeter set to continuity, connect both meter probe ends together, you should hear your meter beep. Next identify both ends of the wire you are trying to test and connect the probes to each end. For example, if you are trying to test the connection between the PCM and the transmission. You'll need to disconnect the PCM connector and identify exactly which pin you are testing. Then with a probe end connected to that PCM connection pin and the other probe end connected to the transmission pigtail pin, you'll hear a beep if the connection is good. Otherwise you know you have an open circuit.

MaroonMonsterLS1

What exactly are you trying to test for continuity? The only thing I can figure is the wiring between the plug on the harness and the ecu? Because to check continuity between the connector on the trans and the internal wiring, you're going to have to drop the pan.
Your post isn't making a lot of sense to me, maybe I'm missing something

Smitty454

Sorry, Im trying to test continuity between the plug and the ECU. I disconnected the plug in the transmission and probed the pins, but im not getting a continuity beep on any of them.

Smitty454

That makes sense. For some reason I thought I could ground one probe and then test the wire with the other for continuity and not actually have to test both ends like when testing for resistance.

So how do I test those wires? Will I have to use a jumper wire from the ECM connection down to the transmission to test both ends?

MaroonMonsterLS1

If you grounded one probe, and just touched the other wires...then you'd be checking them all to ground. Why would you think every single wire in the harness would be grounded?

Have to check at the ecu connector. If that turns up good, check the passthrough connector

ss.slp.ls1

iTrader: (36)

If your probe wires are not long enough to connect one probe to the PCM connector and the other probe to the transmission connector, then yes, run a jumper wire from one or the other to make it long enough.

Smitty454

Ok to simplify it, I need to pop one of the large connectors off the ECU, then test the specific wire that goes to the 2-3 shift solenoid which is the yellow wire with black stripe. One probe goes to that pin and the other probe goes to.....? I guess the issue is I dont know how to test the wire for continuity without actually disconnecting the wire to move it close to the ECU, so I can physically put one probe on each end, unless thats how its done?

Smitty454

Got it! Thank you!