A/T - A140E Diagnosing A No-Shift Problem
BULLETIN: # 038SUBJECT: No Upshift
DATE: February 1991
TRANSMISSION: A140E
DIAGNOSING A NO SHIFT PROBLEM
STEP 1 - 1985 & EARLIER > Go to step 2.
STEP 1 - 1986 & ON CHECK FOR TROUBLE CODES
1. Turn ignition switch to ON.
2. Set O/D switch to OFF.
3. Check that "O/D OFF" lamp on the dash comes on.
"O/D OFF" lamp comes on.
4. Set O/D switch to ON.
"O/D OFF" lamp goes off.
If the light is off, go to step 2.
If the light is flashing, check for trouble codes. Using a jumper lead, connect terminals ECT and E1 at the service connector.
Turn the ignition on (don't start the engine). Turn the OD cancel button off. The OD off light on the dash will flash trouble codes just like a GM computer. Use the chart below to find the problem.
A-140E TROUBLE CODES
If the transaxle still won't shift, Step 2.
STEP 2
Disconnect the throttle position switch (TPS) and see if it shifts. If it does, adjust or replace the TPS.
STEP 3
The neutral start switch may be causing the "no shift" problem.
Check the neutral start switch by disconnecting the wire harness to it and see if it shifts. If it does, adjust or replace the switch.
STEP 4 - 1986 & On > Go to step 5.
STEP 4 - 1985 & Earlier Only Testing The VSS
Turn the engine off.
Locate the SP2 terminal on the computer; this is the # 1 vehicle speed sensor (the main sensor) lead which goes down to the transaxle. With wire harness to the ECT computer disconnected and an ohm meter connected to the SP2 terminal and ground, turn the drive wheels of the car. The ohm meter should fluctuate between zero ohms and infinite resistance.
If the VSS fails the test, then do the same test with the two leads to the VSS at the transaxle.
If the test still fails, check the rotating magnet on the drive pinion for damage and/or replace the VSS.
If the test is OK, check for damaged wires leading to the VSS. One wire goes to body ground and the other goes to the SP2 lead of the ECT computer.
STEP 5 - Quick Checking The Transaxle
Disconnect the wiring harness at the transaxle. Using a wishbone lead (figure 1) attach the single lead to
the positive battery terminal.
Use the chart in figure 2 to shift through the different
ranges by connecting the appropriate wires with the wish-boned jumper lead.
If the transaxle shifts correctly, the no shift condition is external. Go to step 6 checking pin voltage.
If the transaxle doesn't shift, the problem is the valve body, the solenoids, or internal.
STEP 6