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P0988







P0988-4C PRESSURE SWITCH RATIONALITY





For a complete wiring diagram Consult Diagrams/Electrical

Theory of Operation

The Transmission system uses five pressure switches to monitor the fluid pressure in the L/R, 2C, 4C, UD, and OD clutch circuits. The pressure switches are continuously monitored for the correct states in each gear as shown.

- When Monitored:
Continuously with the ignition on, engine running, with the transmission in gear.

- Set Condition:
The DTC is set if the 4C Pressure Switch reads open or closed at the wrong time in a given gear.





Always perform the 45RFE/545RFE Pre-Diagnostic Troubleshooting procedure before proceeding. Testing and Inspection





Diagnostic Test

1. DETERMINE IF RELATED TCM POWER INPUT DTCS ARE PRESENT
With the scan tool, read DTCs.
Are there any TCM Power Input DTCs present also?

Yes

- Diagnose and repair the DTC(s).

No

- Go to2

2. CHECK THE EVENT DATA
With the scan tool, check the Event Data.
Does the Event Data show data for DTC P0988?

Yes

- Go to3

No

- Diagnose and repair the DTC in the Event Data.

3. MULTIPLE DTCS PRESENT
With the scan tool, read DTCs.
Are there two or more related Pressure Switch DTCs present in addition to P0988?

Yes

- Go to4

No

- Go to7

4. RELATED DTC PRESENT
With the scan tool, check the Event Data for P0988.

NOTE: Make sure to record all Event Data stored in the scan tool for future reference in this test procedure.

Do all the pressure switches read CLOSED in the Event Data for P0988?

Yes

- Perform diagnostics for the DTC P0882. P0882

No

- Go to 5

5. EVENT DATA READ OPEN
In the Event Data recorded earlier, do all the pressure switches read OPEN?

Yes

- Go to 6

No

- Go to 7

6. LOW LINE PRESSURE
In the Event Data recorded earlier, is the Line Pressure less than 40 psi, and significantly below the Desired Line Pressure?

Yes

- Repair as necessary to correct low line pressure. Check fluid level and adjust as necessary. If fluid level is OK, check the Primary Oil Filter seal for a split, crack, or improperly installed. If the filter and seal are OK, check the Main Regulator Valve in the Oil Pump.
- Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. Transmission Verification Test

No

- Replace the Transmission Solenoid/TRS Assembly.
- Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. Transmission Verification Test

7. DTC P0871 ALSO PRESENT
With the scan tool, read DTCs.
Is the DTC P0871 also present?

Yes

- Diagnose and repair the DTC(s).

No

- Go to 8

8. EVENT DATA READ PARK REVERSE OR NEUTRAL
In the Event Data recorded earlier, does the Event Data show the DTC set in Park, Neutral, or Reverse for P0988?

Yes

- Go to 13

No

- Go to 9

9. EVENT DATA READ CLOSED
In the Event Data recorded earlier, does the Event Data show the 4C Pressure Switch reading CLOSED?

Yes

- Go to 11

No

- Go to 10

10. PRIMARY OIL FILTER SEAL
In the Event Data recorded earlier, is the Line Pressure less than 40 psi, and significantly below the Desired Line Pressure?

Yes

- Repair as necessary to correct low line pressure. Check fluid level and adjust as necessary. If fluid level is OK, check the Primary Oil Filter seal for a split, crack, or improperly installed. If the filter and seal are OK, check the Main Regulator Valve in the Oil Pump.
- Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. Transmission Verification Test

No

- Go to 15

11. CHECK THE PCM AND WIRING USING THE TRANSMISSION SIMULATOR
Turn the ignition off to the lock position.
Remove the Starter Relay.

CAUTION: Removal of the Starter Relay will prevent the vehicle from being started in gear.

WARNING: The Starter Relay must be removed from the PDC. Failure to do so can result in personal injury or death.

NOTE: Failure to remove the Starter Relay can cause a Transmission - No Response condition.

Install the Transmission Simulator, Miller tool #8333.
Ignition on, engine not running.
With the Transmission Simulator, turn the Pressure Switch selector switch to the 4C position.
With the scan tool, monitor the 4C Pressure Switch while pressing the Pressure Switch test button on the Transmission Simulator.
Did the state of the 4C Pressure Switch change while pressing the Pressure Switch Test button?

Yes

- Go to 12

No

- Go to 13

12. TRANSMISSION SOLENOID/TRS ASSEMBLY
Using the schematics as a guide, inspect the wiring and connectors specific to this circuit.
Wiggle the wires while checking for shorted and open circuits.
Where there any problems found?

Yes

- Repair as necessary.
- Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. Transmission Verification Test

No

- Replace the Transmission Solenoid/TRS Assembly.
- Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. Transmission Verification Test

13. CHECK THE (T48) 4C PRESSURE SIGNAL CIRCUIT FOR AN OPEN




Turn the ignition off to the lock position.
Disconnect the Transmission Simulator, Miller tool #8333.
Disconnect the PCM C4 harness connector.
Connect Miller tool #8815 to the PCM C4 harness connector.

CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller tool #8815 to perform diagnosis.

Measure the resistance of the (T48) 4C Pressure Signal circuit between the Transmission Solenoid/TRS Assembly harness connector and the appropriate terminal of Miller tool #8815.
Is the resistance above 5.0 ohms?

Yes

- Repair the (T48) 4C Pressure Signal circuit for an open.
- Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. Transmission Verification Test

No

- Go to 14

14. CHECK THE (T48) 4C PRESSURE SIGNAL CIRCUIT FOR A SHORT TO GROUND




Measure the resistance between ground and the (T48) 4C Pressure Signal circuit.
Is the resistance below 5.0 ohms?

Yes

- Repair the (T48) 4C Pressure Signal circuit for a short to ground.
- Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. Transmission Verification Test

No

- Using the schematics as a guide, check the Powertrain Control Module (PCM) terminals for corrosion, damage, or terminal push out. Pay particular attention to all power and ground circuits. If no problems are found, replace and program the PCM. With the scan tool, perform Quick Learn.
- Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. Transmission Verification Test

15. NO. 5 CHECK BALL CUT OR DAMAGED
Turn the Ignition off to the lock position.
Remove the Valve Body Assembly.
Inspect the No. 5 check ball for any cuts or damage.
Inspect the 4C accumulator piston and seals and also the 4C tower seal on top of the valve body.
Where there any problems found?

Yes

- Repair as necessary. Check for excessive clutch debris in the transmission oil pan. If excessive clutch debris is present, repair 4C clutch as necessary.
- Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. Transmission Verification Test

No

- Go to 16

16. EXCESSIVE FLUID LEAKAGE WITH 4C CLUTCH CIRCUIT
Air check the 4C Clutch hydraulic circuit.

NOTE: This hydraulic clutch circuit contains a small bleed orifice. Small leakage is considered normal.

Was there excessive air leakage in the 4C Clutch hydraulic circuit?

Yes

- Repair as necessary.
- Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. Transmission Verification Test

No

- Replace the Transmission Solenoid/TRS Assembly.
- Perform 45RFE/545RFE TRANSMISSION VERIFICATION TEST. Transmission Verification Test

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