Transmission Control Module (TCM) - 8HP45

P0563-SYSTEM VOLTAGE HIGH

For a complete wiring diagram Refer to the Wiring Information.

Theory of Operation

The purpose of the diagnostic is to monitor the system voltage level at the Transmission Control Module (TCM). If the TCM supply voltage drops below a calibrated level that is lower than the system voltage, then the high side switch is not activated and DTC P0563 is set.

- When Monitored:
The ignition switch is turned to the run position and engine speed on the CAN BUS greater than a threshold or engine speed on the CAN is invalid

System voltage is greater than a calibrated threshold after TCM startup within a calibrated amount of time

- Set Condition:
The read value does not match the written value in any RAM location.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. 8HP45 Pre-Diagnostic Troubleshooting Procedure

1. CHECK FOR CHARGING SYSTEM DTCS
1. With the scan tool, read Engine DTCs.

NOTE: This includes any one trip faults.

Are any Engine Charging System DTCs present?

Yes

- Repair any Charging System DTCs before proceeding. After repairing the Charging System, perform the Transmission Verification test to verify the transmission and or controller was not damaged. 8HP45 Transmission Verification Test

No

- Go To 2

2. CHECK IF VOLTAGE IS GREATER THAN 16.9 VOLTS
1. Start the engine and raise the engine speed to 2,000 rpm.
2. With the scan tool, monitor the transmission system voltage for 60 seconds.

Does the Transmission system voltage read above 16.9 volts?

Yes

- Go To 4

No

- Go To 3

3. VERIFY IF THE VEHICLE WAS JUMP STARTED WITH 24-VOLT SYSTEM
1. Verify the vehicle was jump started by another vehicle using a 24-volt charging system.

Was the vehicle jump started by another vehicle using a 24-volt charging system?

Yes

- This is the cause of the DTC. Erase the DTC and return the vehicle to the customer.
- Perform the TRANSMISSION VERIFICATION TEST. Verification Tests.

No

- Go To 4

4. CHECK BATTERY VOLTAGE
1. Start the engine and raise the engine speed to 2,000 rpm.
2. With the scan tool, read the transmission system voltage.
3. With a voltmeter, measure the battery voltage at the battery.
4. Compare the readings.

Does the voltmeter reading match the scan tool reading?

Yes

- Repair the charging system for an over charging condition. After repairing the Charging System, perform the Transmission Verification test to verify the transmission and or controller was not damaged.
- Perform the TRANSMISSION VERIFICATION TEST. Verification Tests

No

- Using the schematics as a guide, check the Transmission Control Module Assembly (TCMA) connector 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 TCMA. Valve Body - Removal.
- Perform the TRANSMISSION VERIFICATION TEST. Verification Tests.