II. Diagnosis
FIGURE 2 - VCC ELECTRICAL CIRCUIT (TYPICAL):
FIGURE 3 - CODE E39 ELECTRICAL CHECK:
FIGURE 4 - ROAD TEST:
A schematic of the VCC electrical circuit is shown in Figure 2, for circuit reference purpose. The first step in diagnosing a Code 39 is to perform the "CODE E39 ELECTRICAL CHECK" refer to Figure 3. This check will determine if there is an electrical problem or if a road test required, refer to "ROAD TEST", Figure 4.
FIGURE 3 - CODE E39 ELECTRICAL CHECK:
FIGURE 4 - ROAD TEST:
Notes on Figure 4 - ROAD TEST
1. If the VCC electrical circuit checks good in Figure 3, a road test must be performed to determine if the VCC is applying. The DVOM should remain connected to pin F of the ALDL connector during this test to determine if the ECM is commanding the VCC on. Normal voltage readings from the DVOM are as follows:
Battery volts: Anytime the key is ON and the ECM is NOT commanding VCC operation.
.1 - .4 volts: ECM commanding VCC ON by grounding circuit 422 (status light on).
0.00-0.10 volts: Open exists in VCC electrical circuit, such as when brake is applied (brake
switch opens).
NOTE: The ECM may disable VCC apply for up to 15 minutes after initial start-up.
^ Drive at 50-60 mph with the VCC commanded on (DVOM = .1-.4v) in 4th gear.
^ Tap brake to disable VCC (DVOM = 0.00-0.10v) and note rpm change. Engine speed should increase at least 100 rpm.
2. If no rpm change is noticed, the VCC is not applying. Perform the "Cooler Line Pressure Check", refer to Section III.
3. If the engine speed does increase 100 rpm or greater, the VCC is applying. However, since Code E39 is stored the ECM has detected excessive VCC slippage at some time; and the road test must include "worst case" driving conditions. To induce an excessive VCC slippage driving condition, drive the car under a heavy load, such as up hills. If there are no hills in the test drive area, apply the parking brake while driving. A heavy load condition (driving up hills or park brake applied) would be indicated by a minimum "Manifold Absolute Pressure" (MAP) value of 85 kPa (engine vacuum 4-5" Hg) on 1985-1987 vehicles.
NOTE: Due to the "pump-to-set" parking brake on Eldorado and Seville the service brake can be used in place of the park brake after jumpering circuits 39 and 420 together at the brake switch.
4. Excessive slippage is indicated if the engine speed LOADED is 100 rpm or greater than engine speed UNLOADED at the same vehicle speed. Since the ECM monitors only rpm vs. mph, it does not know if the excessive slippage is due to the VCC or other transaxle components. A Code E39 may be caused by slippage in the 2nd and/or 4th clutches since they are the only clutches that transmit torque in 4th gear. If the 2nd clutch is slipping, a slip or flare should occur during 1-2 upshifts.
FIGURE 4 - ROAD TEST:
5. Normal viscous clutch slippage is 0-75 rpm when VCC is engaged and engine is loaded. Compare the engine rpm and mph readings obtained in the road test to those in Figure 1.
If VCC slippage is NOT excessive, the engine rpm readings from the road test should be at least 100 rpm less than the failure speed listed in Figure 1. If the engine rpm is greater than the failure speed, or within 100 rpm of the failure speed, a speedometer calibration problem may exist.
6. To check for 4th gear slippage, note the engine speed increase when downshifted D4 to D3 at 50 or 60 mph with VCC engaged.
7. If the rpm increase is less than 650 rpm, there is slippage in the 4th clutch. Refer to the appropriate Cadillac Service Information Manual for repairs.
8. If engine speed increases 650-750 rpm when shifted from D4 to D3, 4th clutch is not slipping and there is excessive slippage in the VCC. Refer to Section V for diagnosis and repair.
NOTE ON INTERMITTENT
If all checks indicate normal operation, the problem should be considered intermittent.
To diagnose, the problem must be duplicated while road testing, (manipulating circuits 420 and 422 may be required) monitoring and noting the following readings:
^ voltage at pin F of ALDL connector
^ engine speed (rpm)
DeVille and Fleetwood
- Monitor engine rpm with an external tachometer (Code E39 cannot set in diagnostic mode).
Eldorado and Seville
- Engine rpm can be monitored on the CCDIC ("engine data").
After Code E39 sets and the service soon light comes on:
If pin F voltage = .1 - .4 volts
Check for an rpm change when tapping the brake.
^ If there is no rpm change, refer to Section IV.
^ If the rpm increases, refer to Section V.
If pin F voltage = Battery voltage
There is an intermittent open in circuit 422 between the ALDL and the ECM. Repair open at the ECM connector, edgeboard or circuit 422 wiring. If circuit 422 checks good, perform the "ECM Replacement Check".
If pin F voltage = 0.00-0.10 volts
Repair open that is in either:
^ circuit 420 or, ^ internal transaxle wiring to VCC solenoid and/or VCC overtemp switch or, ^ circuit 422 between the transaxle and the ALDL connector
NOTE: If pin F voltage = 0.00-0.10 volts only after extended driving, the overtemp switch may be opening due to excessive transaxle fluid temperatures. If this is occurring, the switch will close after the transaxle fluid cools. Refer to the Cadillac Service Information Manual for potential causes of transaxle overheating.