A/T - Diagnosis/Measuring Block Values: Overview
Subject: Transmission diagnosis/measuring block values
Model(s): Passat, with Automatic Transmission m.y. 1990-1991 up to VIN ME 024 471
Group: D3
Number: 91-01
Date: January 31, 1991
Transmission diagnosis
Repairs to the 096 4-speed automatic transmission must not be started until the following diagnosis procedure has been performed.
Remedy each problem found during the procedure and if repairs are made, road test the vehicle again before continuing to the next numbered diagnosis step.
1 Test drive vehicle
^ test drive to verify customer complaints (if possible let customer drive)
2 Check for leaks
^ check vehicle for visible leakage of ATF from transmission and cooler lines or hypoid oil from differential
3 Check ATF level
Use the procedure described in the Repair Manual, Group D3, to connect tester VAG 1551. The transmission diagnosis program 09, channel 03, shows the proper operating temperature for accurately checking the ATF level. The procedure outlined in Technical Bulletin, Group 32, No. 90-01, can also be used to check the ATF level.
Note
ATF in the 096 transmission is reddish in color when new but soon discolors to a dark brown/ black. A dark brown/black color is normal.
After connecting the VAG 1551, note the Part Number for the Digimat (transmission) ECU, as well as the Part Number for the Motronic ECU.
If repairs to the transmission are necessary, a complete printout of the VAG 1551 diagnosis will be required. Switch the printer on for all diagnosis functions performed and save the resulting printout. The printout can then be attached to the repair order if necessary.
4 Check for ATF contamination
If ATF is mixed with engine coolant or water it can have a milky appearance and be somewhat lighter in color. Causes for such fluid mixing can be due to leaks at the dipstick (water) or a faulty transmission ATF cooler (high ATF level combined with low coolant level).
5 Fault check using VAG 1551
Refer to the Repair Manual, Group D3, for complete instructions on recalling the Digimat ECU fault memory with VAG 1551.
^ if faults have been recorded, follow the directions in the fault chart to locate the cause of the fault and make the necessary repairs
6 Measuring value check with VAG 1551
^ if no faults are recorded or if the problem still exists after repairs, use the VAG 1551 tester to read measuring value block (08) and individual measuring values (09) (see pages 5 through 10 of this Technical Bulletin)
7 Stall speed test
Perform stall speed test as follows:
^ check that engine is at operating temperature
^ connect tachometer (see Repair Manual, section 25-70)
^ start engine and hold vehicle firmly with parking brake and foot brake
^ move selector lever to D position and briefly accelerate engine to full throttle
^ check that engine runs at approximately 2700 RPM
CAUTION
Do not continue the stall speed test longer than the time required to read the tachometer. The maximum stall speed test time is 5 seconds. If it is necessary to repeat the test, wait at least 20 seconds.
Note
Normal stall speed will drop 125 RPM per 3200 feet of altitude. Stall speed will also drop slightly at high ambient air temperatures.
^ if stall speed is below 2500 RPM transmission problem is possibly related to poor engine performance
^ if stall speed is above 2700 RPM, torque converter or internal transmission problems are likely and component must be repaired or replaced
8 Check engine performance
If the transmission complaint is:
a delayed shifting
or
b rough downshifting (mostly 4-3 shift)
Often the ignition retard system or knock sensor system is not functioning properly. Refer to the Repair Manual for instructions on checking the ignition timing with VAG 1367 and perform the additional steps below:
^ check that operating temperature of engine is between 60~ - 80~ C (140~ - 176~ F)
^ check engine timing and adjust to 6 +/- l~ BTDC
CAUTION
Two mechanics are required to perform the following checks.
^ drive vehicle and conduct 3 or 4 brief wide open throttle accelerations
^ check that timing is between - 1~ and + 19~ during acceleration at 2000 RPM
^ if timing is retarded more than - 6~ check knock sensor torque and connections and test again
^ if OK, road test vehicle to determine if transmission problem has been eliminated
9 Check Motronic ECU
If transmission problem still exists, check if latest level Motronic ECU is installed; replace if necessary and road test vehicle.
^ Motronic ECU: Part No. 893 907 404 0 (California) Part No. 8A0 907 404 (49 state)
10 Check fuel quality
11 Check Digimat ECU
Complants of poor shift quality can possibly be eliminated by installing a later Digimat ECU. Refer to the current ECU Part No. and check with your Parts Department for the latest version. Replace the Digimat ECU if necessary.