P0770

P0770-4C SOLENOID CIRCUIT





For a complete wiring diagram, refer to the Wiring Information.

Theory of Operation

The Transmission Control System uses six electronically controlled solenoids that allow hydraulic fluid to be applied to various friction elements (clutches), which enables the gear requested. The continuity of each solenoid circuit is periodically tested. Each inactive solenoid is turned on for a few milliseconds, then off. Each active solenoid is turned off for a few milliseconds, then on. This pulsing of voltage to the solenoid causes an inductive spike which can be sensed by the Transmission Control System. If an inductive spike is not sensed by the Transmission Control System during the continuity check, it is tested again. If the test fails three consecutive times, the appropriate Diagnostic Trouble Code (DTC) is set. If the solenoid test is run in response to a gear ratio or pressure switch error, one failure will result in setting the appropriate DTC.

- When Monitored:
Initially at power-up, then every 10 seconds thereafter. The solenoid circuits will also be tested immediately after a gear ratio or pressure switch error is detected.

- Set Condition:
After three consecutive solenoid continuity test failures, or one failure if test is run in response to a gear ratio or pressure switch error.
NOTE: This DTC is strictly an electrical fault and cannot be caused by any internal transmission failure other than an open in the Transmission Solenoid/TRS Assembly. If the Transmission Solenoid/TRS Assembly is in need of replacement - do not replace the Valve Body.





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

1. CHECK DTCS
1. With the scan tool, read DTCs.

Are there any TIPM TCM Power Control Circuit or TCM Power Input DTCs present?

Yes

- Testing and InspectionPerform the appropriate diagnostic procedure.

No

- Go To 2

2. CHECK IF DTC P0770 IS PRESENT
1. Ignition on, engine not running.
2. With the scan tool, erase all Transmission DTCs.
3. Turn the ignition off to the lock position.
4. 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 may result in possible serious or fatal injury.

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

5. Install Transmission Simulator 8333.
6. Ignition on, engine not running.
7. With the scan tool, actuate the 4C Solenoid.
8. Monitor the 4C Solenoid LED on the Transmission Simulator.

Did the 4C Solenoid LED on the Transmission Simulator blink on and off?

Yes

- Go To 3

No

- Go To 5

3. CHECK THE TRANSMISSION SOLENOID/TRS ASSEMBLY
1. With the Transmission simulator still connected, continue to actuate the 4C solenoid for two minutes.
2. After two minutes of actuation, with the scan tool, stop the actuation and check for transmission DTCs.

Did the DTC P0770 reset during the actuation test?

Yes

- Go To 5

No

- Go To 4

4. CHECK THE TRANSMISSION SOLENOID/TRS ASSEMBLY
1. With the Transmission simulator still connected, continue to actuate the 4C solenoid for another two minutes while wiggling the related wiring harness and connectors.
2. With the scan tool, stop the actuation and check for transmission DTCs.

Did the DTC P0770 reset during the actuation test?

Yes

- Repair wiring harness or connectors as necessary.
- Perform the 545RFE TRANSMISSION VERIFICATION TEST. . 545RFE Transmission Verification Test

No

- Replace the Transmission Solenoid/TRS Assembly.
Note: Do NOT replace the entire Valve Body.
- Perform the 545RFE TRANSMISSION VERIFICATION TEST. . 545RFE Transmission Verification Test

5. CHECK THE (T259) 4C CONTROL CIRCUIT FOR A SHORT TO ANOTHER CIRCUIT




1. Turn the ignition off to the lock position.
2. Disconnect the Transmission Simulator 8333.
3. Disconnect the PCM harness connectors.
4. Measure the resistance between the (T259) 4C Control circuit and all other circuits in the Transmission Solenoid/TRS Assembly harness connector.

Is the resistance below 5.0 Ohms between the (T259) 4C Control circuit and any other circuit(s) in the Transmission Solenoid/TRS Assembly harness connector?

Yes

- Repair the (T259) 4C Control circuit for a short to another circuit(s).
- Perform the 545RFE TRANSMISSION VERIFICATION TEST. . 545RFE Transmission Verification Test

No

- Go To 6

6. CHECK THE (T259) 4C CONTROL CIRCUIT FOR AN OPEN




1. Connect the PCM Pinout Box 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 the PCM Pinout Box 8815 to perform diagnosis.

2. Measure the resistance of the (T259) 4C Control circuit between the Transmission Solenoid/TRS Assembly harness connector and the appropriate terminal of the PCM Pinout Box 8815.

Is the resistance above 5.0 Ohms?

Yes

- Repair the (T259) 4C Control circuit for an open.
- Perform the 545RFE TRANSMISSION VERIFICATION TEST. . 545RFE Transmission Verification Test

No

- Go To 7

7. CHECK THE (T259) 4C CONTROL CIRCUIT FOR A SHORT TO GROUND




1. Measure the resistance between ground and the (T259) 4C Control circuit.

Is the resistance below 5.0 Ohms?

Yes

- Repair the (T259) 4C Control circuit for a short to ground.
- Perform the 545RFE TRANSMISSION VERIFICATION TEST. . 545RFE 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. Quick Learn Procedure
- Perform the 545RFE TRANSMISSION VERIFICATION TEST. . 545RFE Transmission Verification Test