Hydraulic Pressure Tests
CAUTION:
Parking and service brakes must be applied throughout hydraulic pressure test. Total time for testing with vehicle in any driving gear should not exceed 2 minutes. Transmission damage may occur.
- Before performing hydraulic pressure test, check fluid level and condition. Check manual control linkages for correct adjustment, and ensure engine is properly tuned.
- Connect scan tool to Data Link Connector (DLC). Apply parking brake and start engine. Check for stored trouble codes. If trouble codes are present, diagnose as necessary. See 4L80-E ELECTRONIC CONTROLS - 1995 article in the TRANSMISSION SERVICING SECTION or 4L80-E ELECTRONIC CONTROLS - 1996 article. Turn engine off. Connect oil pressure gauge to line pressure test port. See Fig 1.
- Start engine and warm to normal operating temperature. With vehicle in Reverse, line pressure should be 67-324 psi (462-2234 kPa). With vehicle in Park, Neutral or Drive, line pressure should be 35-171 psi (241-1179 kPa).
- Shift transmission into Park. Access Pressure Control Solenoid (PCS) test on scan tool. Increase DESIRED PCS in 0.1 amp increments and read corresponding line pressure on oil pressure gauge. Allow pressure to stabilize for 5 seconds after each current change. Compare readings to LINE PRESSURE SPECIFICATIONS . If pressure readings are not as specified, and no trouble codes are present, internal malfunction exists. See TROUBLE SHOOTING .
NOTE:
Scan tool is only able to control pressure control solenoid in Park and Neutral with vehicle stopped. This protects clutches from extremely high or low pressures in Reverse and Drive.
LINE PRESSURE SPECIFICATIONS
| PCS Current (Amp) | Line Pressure: psi (kPa) |
|---|---|
| 0.02 | 157-177 (1082-1220) |
| 0.10 | 151-176 (1040-1213) |
| 0.20 | 140-172 (965-1186) |
| 0.30 | 137-162 (944-1117) |
| 0.40 | 121-147 (834-1013) |
| 0.50 | 102-131 (703-903) |
| 0.60 | 88-113 (606-780) |
| 0.70 | 63-93 (434-640) |
| 0.80 | 43-73 (296-503) |
| 0.90 | 37-61 (255-420) |
| 0.98 | 35-55 (241-380) |