Issue Summary:
- After re-installation, the transmission in a Nissan Quest/Mercury Villager is stuck in third gear, line pressure is at a maximum level and the inhibitor-switch circuits do not range correctly. Solenoid codes also may be present.
- The Audi 01F/01K transaxle (ZF 4HP-18FLE/FLA) may have a vent cap mounted on top of the transmission filler tube instead of a dipstick.
- In GM electronically controlled transmissions, false output signals can cause complaints including no TCC apply, wrong-gear start, missing gears, falling out of gear, or line-pressure control problems.
- When removing the allen-style torque-converter bolts in 4L60-E and 4L80-E transmissions, a technician may find them difficult to remove and possibly round out the internal hex slots.
- 1999-2002 4WD trucks with a New Venture Gear 236/246 transfer case may experience a “Service 4WD” indicator light that remains on, possibly accompanied by Service Code B2725 (ATC Mode Switch Circuit Malfunction).
- An electronically shifted GM transmission may exhibit late 2-3 and 3-4 shifts under heavy-throttle conditions but seem to operate properly under normal throttle conditions. It also may have an elongated forced detent shift with no increase in vehicle speed that may require the driver to back off the throttle to complete the shift.
After re-installation, the transmission is stuck in third gear, line pressure is at a maximum level and the inhibitor-switch circuits do not range correctly. Solenoid codes also may be present.
The F21/F22 ground attachment shown in Figure 1 has not been tightened or has been left off. This is the main TCM ground at terminals 15 and 48 of the TCM. The F21/F22 ground is in the area of the 2/4-band-servo cover and also retains the filler-tube mounting bracket. When this ground is lost, the complaints mentioned will occur.
Make certain the F21/F22 ground is attached, tight and clean before the ignition is turned on!
The Audi 100 uses a transaxle that Audi calls a 01F/01K. It is ZF’s 4HP-18FLE/FLA. When you reach for the dipstick to check the transmission fluid, you discover that a vent cap is mounted on top of the tube instead (see Figure 2). With a little further investigation you find that the dipstick for this vehicle is considered a tool to be purchased using part # 01F 321 431 A with ID markings of “02” (see Figure 7) and part # 01 F 321 431 B with ID markings of 03. So when you call Audi to order the stick, the dealer says it is a $21 tool, it’s not in stock and will require several days for shipping if you order it. Now what?
Figure 3 provides dimensions for both the 02 and 03 sticks so that you can make your own.
In June 1994, Audi eliminated the tube entirely, and a check-and-fill plug is on the side of the pan as shown in Figure 4.
Some of the transmission-related complaints may be no TCC apply, wrong-gear start, missing gears, falling out of gear, or line-pressure control problems. No codes are stored, and the scan tool indicates that all signals are operating normally!
The cause could be the computer’s internal driver circuit, a faulty cold-solder joint on the computer’s circuit board, or a wire or connector problem. The reason why no related codes are stored and the scan tool indicates that the outputs are operating normally (see Figure 5) is that downstream of the computer’s diagnostic checkpoint, in the output circuit, the target voltage is incorrect, while at the diagnostic checkpoint in another area of the computer’s circuit board, the target voltage is correct.
Use a digital multimeter to check the actual signal (refer to Figure 6) on the circuit in question. In this example, a 4L60-E PWM solenoid’s voltage should ramp from low to high (system voltage) on the solenoid’s ground side, which means TCC is fully applied and the voltage seen at this time on the ground circuit should be system voltage because the solenoid is turned off. Duty cycle will be zero only when the enable solenoid is on. Transmissions that use this type of operation are 4L60-E and 4T60-E.
Early 4T60-Es displayed duty cycle from 100% to 0%, indicating percentage of on time.
Late 4T60-Es and 1995-and-later 4L60-Es display duty cycle from 0% to 100%, indicating the percentage of off time; however, solenoid operation is identical.
PWM TCC-solenoid operation would be different on a transmission with only a PWM TCC solenoid, such as a 4T65-E, 4T80-E or 4T40-E. The computer will produce up to 98% duty cycle for maximum TCC apply, which means the solenoid is fully on and less than 1 volt would be seen on the PWM-solenoid ground circuit.
If it is a duty-cycle type of solenoid, set your multimeter to Duty Cycle (%) or Voltage; if it is an on/off solenoid set your multimeter to DC Volts and use the meter’s MIN/MAX feature. If it is a variable-type solenoid, set your multimeter to Amps or Duty Cycle.
Note:
It is a good practice to compare the signal you see on a scan tool with the same signal you see on a multimeter.
When removing the allen-style torque-converter bolts, the technician may find them difficult to remove and possibly round out the internal hex slots.
A combination of bolt design and exposure to the elements.
GM has released a new-style bolt with internal/external hex head to replace the previous design (see Figure 7).
- Torque-converter bolts (6), external/ internal hex design . . . . . . . . .Part # 11519291
1999 to 2002 four-wheel-drive trucks with a New Venture Gear 236/246 transfer case (RPO NP8) may experience a “Service 4WD” indicator light that remains on. A Service Code B2725 (ATC Mode Switch Circuit Malfunction) may accompany this concern.
An intermittent fault in the transfer-case select switch may be causing this condition. The transfer-case control module should not be immediately suspected or replaced unless it has been determined to be faulty.
The transfer case select (push-button) switch contains four normally open switches (see Figure 8) and is in the center of the instrument panel, to the right of the steering-column shift lever. The driver uses this switch to select the desired transfer-case operation. The switch selection sends the appropriate signal to the transfer-case control module, which is to the left of the instrument cluster behind the headlamp switch on full-size trucks and behind the passenger-side kick panel on Blazer-type trucks. This module provides an 8-volt reference to the switch’s C1 connector at terminal A. If no buttons are pressed, the switch sends back to the module a 0.5- to 1.0-volt signal in its C1 connector at terminal F16.
The chart in Figure 9 shows this and the other values for the transfer-case select switch.
Should the module detect a voltage level outside this range for longer than 5 minutes, the module will set code B2725. Simultaneously, the module will ground the wire at terminal E2 in its C1 connector, illuminating the “Service 4WD” light in the instrument cluster.
Note:
The NV236/246 transfer cases do not have a button on the transfer-case select switch for Neutral; however, neutral can be obtained through the transfer-case select switch when the following conditions have been met:
- The engine must be running.
- The automatic transmission must be in neutral,
- Vehicle speed is below 3 mph.
- The transfer case is in the 2HI mode.
Once these conditions have been met, neutral can be obtained by pressing and holding the 2HI and 4LO buttons simultaneously for 10 seconds, at which time the red neutral indicator lamp will illuminate and the transfer case will shift to neutral.
Replace the transfer-case select switch or the transfer-case control module (TCCM) only if necessary.
- Transfer-case select switch………………15709327
- Transfer-case control module …………..15749703
The transmission exhibits late 2-3 and 3-4 shifts under heavy-throttle conditions but seems to operate properly under normal-throttle conditions. The transmission also has an elongated forced detent shift with no increase in vehicle speed that may require the driver to back off the throttle to complete the shift.
The cause may be a restricted fuel filter (see Figure 10) rather than an actual transmission problem.
Note:
This complaint also can be caused by other parts related to fuel supply, such as the fuel-pump strainer and fuel pump inside the fuel tank.
Have a fuel-flow and fuel-pressure test performed, and replace fuel filter if results are below specs.
November 2003 Issue
Volume 20, No. 11
- Nissan Quest: Mercury Villager
- Audi 100: 01F/01K (ZF-4HP-18FLE/FLA)
- GM Electronically Controlled Transmissions: False Output Signals
- GM 4L60-E & 4L80-E: New-Design Converter Bolts
- 1999-2002 4WD GM Trucks: Service 4WD Indicator Illuminated
- GM Electronically Shifted Vehicles: Late Shifts