GMC Envoy Electronic Throttle Body Testing

I’m still trying to figure out what is going on with the Envoy transmission.  I’ve replaced some of the electronics in the transmission, reset the computer, and various other fixes.  Nothing seems to have worked.  Since I’m not completely convinced that the transmission is mechanically bad, I’ve done some research on the 4L60E transmission that is in the Envoy.  I found this article on the internet that gives some ideas as to what the issues may be. 

One of the issues that could present the symptoms that I am experiencing seems to be the TPS (Throttle Position Sensor).  The issue that I am experiencing is a pretty hard jerk into Drive and reverse, plus slightly rougher than normal shifting between gears.  However, there is no slipping and the fluid is red. 

Since the 07 Envoy has an electronic throttle body that actually has 2 TPS sensors in it i thought we may be onto something. I then found this article that shows how to test the functionality of the TPS and throttle body. 

So you will need a multi-meter to perform these tests.  You will also need to do some minor disassembly of the intake to get to the throttle body.  All of these tests can be done with the throttle body still in the car.

Start with the disassembly.  Use a flat head screwdriver to loosen the two screws that are tightening the round clamps to the throttle body and plastic plenum.

Clamp on the Plenum
Clamp on Throttle Body

Then take a 10mm socket with extension to loosen the two bolts that hold the plastic plenum onto the motor.  Take note of the rubber hose towards the front that is connected to the valve cover.  This will need to be re-connected when you re-assemble.

Front 10mm Bolt for Plenum
Rear Plenum Bolt

Move the plastic plenum out of the way.

Disconnect the electrical connector from the throttle body.

Now you will use the resistance setting on the multi-meter tool

The first test that you will be doing is testing the resistance between terminals C and G.  All you are looking for is continuity for the circuit.  You will get no reading if this circuit is broken, so all your looking for is some kind of reading from the multi-meter.

The next test is to make sure that the TPS is reading the position of the butterfly as it opens.  You will want to test this resistance while slowly opening and closing the throttle by hand.  This is a little tricky by yourself but it can be done.  The connectors that you will want to use are A and G, the resistance should slowly increase as the butterfly opens and as it closes will decrease slowly.  If you see any points where it stops or jumps around, there is a problem.

You still need to test the second TPS sensor that is in the throttle body.  The first test is similar to the first test above but on different terminals.  You will be looking for some kind of reading between terminals B and H.

And the second test for TPS 2 would be the butterfly test.  Just like the first test where you open the butterfly by hand, you will open it again and look for changes in resistance as you open and close the throttle, only this time it will decrease as you open it and increase as you close it.  The terminals are B and D.

There is also one more test that you can do with your multi-meter to make sure that the throttle body is in proper working condition and that is for the actuator motor.  This was not really of much interest to me at this point because I thought my issue was going to be with the TPS’s but I already had everything apart so might as well…..

The only test that you can do to the actuator motor is to see if it has suffered and open circuit or break in the connection.  You will be testing resistance from terminals E and F, if you get any reading at all, it is a good indication that the actuator motor is in working order.

Well, all this testing did nothing to solve my transmission issues but I did it and found that my Electronic throttle body was in good working order.  I will continue (maybe) to look for another reason for the hard shift into drive.  Maybe I’ll actually find it someday.

No Responses

Leave a Reply