It does not necessarily mean the trans is ba it could just be a sensor but read testing should help find probblem thank you
Since some of these tests require the drive wheels be raised off the ground and the engine and transmission run in gear, proper care must be taken to perform the tests in a safe manner. Support the vehicle with jack stands. NEVER run the vehicle in gear when supported only with a jack. Chock the drive wheels and apply the parking brake.
In addition, some of the tests (test #11 and 12) require the transmission be opened and the valves be physically inspected. I do not recommend that you do this. If all the other tests pass, then it's time to bring it to a shop and have the internal parts checked for proper operation.
Test #1 (Quick Method)
Check For 12 Volts To Terminal A At The ALDL
Note: ALDL quick methods, when given, are a way to perform many of the tests at the Assembly Line Diagnostic Link (ALDL). This will allow you to do most of the electrical checks from the driver's seat and save much valuable diagnostic time.
Connect one end of a test light to terminal A at the ALDL.
Connect the other end to terminal F at the ALDL.
Turn on the ignition and the tester should light. Note: some transmissions, like the 125C must shift to 3rd before the tester will light.
If the tester lights, you have 12 volts to terminal A at the transmission. Go to Test # 6.
If the tester does not light, then check for 12 volts by the regular method.
Test #2
Checking For 12 Volts Across Fuse
Check for 12 volts at both sides of the fuse.
Locate the fuse box and the fuse marked "gauges" (most models).
Connect the alligator clip of your test light to ground. Turn the ignition on.
Place the tip of your test light on one side of the fuse and the tester should light.
Place the tip of your test light on the other side of the fuse and the tester should again light.
Test #3
Checking For 12 Volts Across Brake Switch
IMPORTANT: Either of these switches can be used for lock-up. To avoid mis-diagnosis, check them both. If the upper switch with the vacuum hose is used, check the two wires at that switch. On the four wire lower switch, check the two wires farthest from the plunger.
Check for 12 volts at both sides of the brake switch. Some GM vehicles have two electric switches at the brake pedal. One switch will have four wires and the other switch will have two wires and a vacuum hose.
Connect the alligator clip of your test light to ground.
Do not depress the brake pedal.
Turn the ignition "on".
Push the tip of your tester into one wire and the tester should light.
Now test the other wire and again the tester should light.
Depress the brake pedal and re-test. Only one wire should now be hot.
Test #4
Adjusting/Replacing the Brake Switch
Remove the brake switch from its bracket.
Reconnect the wires to the brake switch.
Re-test as stated in test # 2, but push and release the plunger with your finger or thumb.
If it now passes the test, the brake switch is good, but needs adjusting.
If it still doesn't pass, replace the brake switch.
Test #5
Checking Wires For Shorts and Opens
IMPORTANT: Make sure the ignition switch is "off" for the following tests.
Shorts:
Set your ohmmeter to ohms times one (Rx1).
Connect one lead of your ohmmeter to one end of the suspect wire.
Connect the other lead of your ohmmeter to a good ground.
If the meter reads ANYTHING other than infinity, you have a short to ground in that wire.
Opens:
If a suspect wire has no voltage through it, and its connection at both ends is good, and it's not shorted to ground, the wire has an open in it.
Replace the wire.
Test #6 (Regular Method)
Check for ground at terminal D at the transmission.
On Non-computer-controlled vehicles skip this test and go directly to cooler line pressure, or surge test.
Raise the vehicle on the lift so the driving wheels are off the ground.
Unplug the wires at the case and connect the alligator clip of your test light to terminal A.
Place the tip of your test light on terminal D.
Start the engine and bring to normal operating temperature.
Place the selector in Drive. (O.D. On four speed units).
Accelerate slowly to 60 mph and the tester should light.
If the tester does not light you have a computer system problem. Go to test # 7 (Regular Method).
Test #6 (Quick Method)
Check for ground at terminal D at the ALDL
Note: First you must have passed ALDL Quick method (Test # 1. Otherwise continue with regular method Test # 6).
The test light should still be connected between terminal A and F at the ALDL.
With the engine at normal operating temperature, go for a road test
As you start your road test the tester should be lit.
Note: If your foot is on the brake the light will be out.
Watch the test light to see if it goes out at some point during the road test
If the test light goes out, you have ground at terminal D at the transmission. Go to test # 7.
If the test light stays on you have a computer system problem. (See test # 13) Go test # 7.
Test #7 (Regular Method)
Ground the D wire at the transmission
Shave a little insulation from or pierce the D wire near the transmission connector. Reseal with silicon.
Connect one end of a jumper wire to the bare wire you just shaved or pierced.
Connect the other end of the jumper wire to ground.
Road test for lock-up (can be done on lift).
If you're not sure if lock-up occurred, then hold a steady speed of 60 mph (on the lift) and lightly touch and release the brake. You should feel lock-up disengage and re-engage.
Test #7 (Quick Method)
Ground the D wire at the ALDL
Note: You must first have passed ALDL Quick method (Test # 1).
Connect one end of a test light or jumper wire to terminal A at the ALDL.
Go for a road test. (This can also be done on the lift)
At approximately 35 mph, connect the other end of the test light or jumper wire to terminal F at the ALDL. The torque converter should Lock-up.
Whether the T/C locks up or not, follow the trouble-shooting tree to the next step, cooler line surge test.
Test #8
Checking Cooler Line Pressure or Surge
Check cooler line pressure or surge.
Disconnect a cooler line.
Attach one end of a rubber hose to the disconnected line coming from the radiator.
Insert the other end of the rubber hose into the fill tube of the transmission.
With the driving wheels off the ground, start the engine. Hold the rubber hose in your hand. Have as assistant place the selector in Drive and (slowly) accelerate to 60 mph. When the lock-up valve moves, the rubber hose should jump slightly.
Test #9
Checking the Solenoid
You will need an ANALOG ohmmeter and a 12-volt source for this test.
Connect the Black lead of your ohmmeter to the RED wire on the solenoid.
Connect the RED lead of your ohmmeter to the BLACK wire on the solenoid. If you have a one-wire solenoid then connect the RED lead of your ohmmeter to the solenoid body.
With the ohmmeter set at ohms times one (Rx1), the reading should be no less then 20 ohms, but not infinite.
Connect the RED lead of your ohmmeter to the RED wire on the solenoid and the Black lead to the Black wire or body (You're just switching your connections).
The ohmmeter should read less than the reading in the first test.
Connect the solenoid to a 12-volt source. BE SURE TO OBSERVE PROPER POLARITY, if using a car battery.
With lung pressure (or very low pressure) try to blow through the solenoid. It should be sealed.
Disconnect the 12-volt source and you should now be able to blow through the solenoid.
Test #10
Checking Electrical Switches on Transmission
Note: If you have passed the ALDL Quick methods, the electrical switches are NOT causing the any lock-up condition. Go to test # 11.
SWITCH TYPE: Single terminal normally open
PART#: 8642473
TEST: Connect one ohmmeter lead to the terminal of the switch and the other lead to the body of the switch. Ohmmeter should read infinite. Apply 60 psi of air to the switch and the ohmmeter should read 0.
SWITCH TYPE: Signal terminal normally closed
PART#: 8642569, 8634475
TEST: Connect one ohmmeter lead to the terminal of the switch and the other lead to the body of the switch. Ohmmeter should read 0. Apply 60 psi of air to the switch and the ohmmeter should read infinite.
Test #11
Checking Lockup Apply Valve (Requires disassembly)
Test #12
Checking Signal Oil Circuit (Requires disassembly)
Wednesday, October 15th, 2008 AT 4:33 PM
