Can some one help me to test the external wire harness for resistance. I am not doing g something right. I can test and get 12 volts at pink wire. Now I want to check for resistance. I tried checking with DMM set to ohms. Tried to test for the solenoids. T to E, A to E, B to E, S to E and U toe. I am not getting any readings. There has to be resistance on something. Tried with key on and off. 2004 trailblazer. Please help if you can. I am trying make sure the external harness is good before going into removing g pan to test solenoids.

 

A little late, but here goes. The external harness goes from the trans to the PCM, the internal harness is the one that has the solenoids connected to it. If you unplug the external harness from the trans and check the connector, you should have 12 volts at the pink wire (E) and you should not be getting much of a reading from any of the others as you are reading the PCM circuits.



To check the solenoids you have to connect your meter to the internal trans harness connector on the trans itself. Easiest way to do this is to make a test connector, simply cut the external harness off one at a junk yard and label each wire with a masking tape tag with the terminal letter. Strip the end of each wire and connect the meter to the proper wires to test a particular solenoid. Plug it into your trans and you should get the correct readings if the solenoid and internal harness are OK. You can also back probe the external harness while it is plugged into the transmission (key off) and measure the resistance that way. With the PCM attached the readings may be off a few ohms though. The solenoids attached to the E terminal should also show 12 volts on the other terminal with the key on.


If you're getting solenoid electrical codes but the solenoids test good at the trans connector, you need to check for the same readings at the PCM connector to verify the external harness wiring between them is intact.


Also, take a mirror and a flashlight and check the terminals inside the trans connector. The pins can be damaged or even pushed down into the connector, creating a bad or no connection.