Issue Summary:
- The LJ4A-EL transaxle in a Mazda Millenia with a 2.3-liter (KJ) engine can experience severe friction damage and premature failure.
- Before or after overhaul, Volkswagen/Audi vehicles equipped with 01M, 01N and 01P transaxles may exhibit a harsh 1-2 upshift, firmer-than-normal engagements, and firm upshifts to 3rd and 4th.
An LJ4A-EL transaxle in a Mazda Millenia with a 2.3-liter (KJ) engine has come into your shop having suffered severe friction damage. After repairs it returns to the shop with the identical damage but no codes present. Repeat repairs are made, the transaxle is placed back into the car and the line pressure is checked. Line at idle is about 60 psi in Drive. At stall, line pressure never gets higher than 80 psi. A line-pressure solenoid is replaced, but the problem remains. A pinpoint check at the computer using factory-supplied specifications determines that the throttle-position sensor (TPS) is ranging correctly (see Figure 1).
It is also noticed that the computer is not commanding the pressure-control solenoid to raise line pressure. Continued checks are made, but all inputs are found to be ranging according to factory specifications. So the computer is replaced, and the problem of insufficient line rise remains.
The factory voltage specifications for the TPS are 0.1 to 1.2 volts DC at closed throttle and 3.5 to 4.0 volts DC at wide-open throttle. This is incorrect. Voltage at closed throttle must be above 0.3 volt. If it is not, the computer will not respond to the voltage sweep of the TPS and therefore will not command line rise at the pressure-control solenoid. This incorrect factory specification will not produce a diagnostic trouble code (DTC).
What has been known to occur is that the vehicle originally goes into a shop or dealer for a tune-up. During this time, the technician adjusts the TPS to factory specification, not knowing that adjusting the TPS down to 0.1 to 0.3 volts at closed throttle will cause a transmission problem. Sometime after the tune-up, the transmission develops a slip and burns, and the vehicle owner takes it to a transmission shop for repairs.
Adjust the TPS closed-throttle voltage to a minimum of 0.5 to 0.6 volt. Double-check with a pressure gauge (see Figure 2), verifying that line rise has returned to proper working order.
Factory line-pressure specifications are:
Before or after overhaul, vehicles equipped with 01M, 01N and 01P transaxles may exhibit a harsh 1-2 upshift along with firmer-than-normal engagements and firm upshifts to 3rd and 4th.
The cause may be:
- Erratic or high line pressure.
- An electrical malfunction in the EV5 solenoid electrical circuit.
- A hydraulic malfunction with the EV5 solenoid.
(NOTE: The EV5 solenoid is grounded on each engagement and each upshift and downshift, which helps control clutch apply pressure for smooth engagements (see figures 3 and 4).
Connect a pressure gauge to the line-pressure port (see Figure 5). Line pressure should indicate 60 psi in the Drive position at idle and should increase to 120-150 psi at stall.
Line pressure should cut back to 65-75 psi on each shift. If line pressure does not cut back on each shift, is at 120-150 psi at all times or is erratic on the gauge, replace the EV6 solenoid and check the boost regulator valve and main regulator valve to ensure that they are not stuck. Refer to Figure 6 for a description of how the EV6 solenoid operates.
2. Referring to Figure 7, locate terminal 7 at the harness connector. Back-probe that terminal to verify that the computer is grounding EV5 during the 1-2 upshift. If the computer is not grounding that terminal, go to Step A. If the computer is grounding that terminal, go to Step B.
STEP A. Connect a scan tool to the diagnostic connector and check to see whether the TCM has set trouble code 00266 (VAG) or P0773, both of which are EV5-solenoid circuit faults. Repair the EV5 solenoid circuit as needed. If the TCM has no trouble codes set and does not ground the EV5 solenoid during the 1-2 shift, the TCM may be faulty.
STEP B. Go to correction number 3.
Remove the EV5 solenoid from its bore. Ensure that the B1 apply valve, which is below the solenoid, is not sticking in its bore. Air-check the EV5 solenoid and ensure its proper operation (refer to Figure 8). If the EV5 solenoid does not close consistently, replace as needed.
May 2003 Issue
Volume 20, No. 5
- Mazda Millenia: Premature Transaxle Failure
- Volkswagen/Audi: Uncontrollable Harsh 1-2 Upshift