DTC P0788 5.3L and 6.0L
Circuit Description
The 3-2 shift solenoid (SS) valve is a normally-closed, 3-port, ON/OFF device that controls the 3-2 downshift. The solenoid attaches to the control valve body within the transmission. The solenoid receives voltage through the ignition voltage circuit. The transmission control module (TCM) controls the solenoid by providing a ground path on the 3-2 shift solenoid valve control circuit. During a 3-2 downshift, the 2-4 band applies as the 3-4 clutch releases. The TCM varies the timing between the 3-4 clutch release and the 2-4 band apply depending on the vehicle speed and throttle position.
When the TCM detects a continuous short to voltage in the 3-2 shift solenoid valve control circuit, then DTC P0788 sets. DTC P0788 is a type A DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0788 3-2 Shift Solenoid (SS) Control Circuit High Voltage
Conditions for Running the DTC
| • | The system voltage is 8-18 volts. |
| • | The engine speed is 475 RPM for 5 seconds. |
| • | Vehicle speed. |
Conditions for Setting the DTC
DTC P0788 sets if the TCM commands the solenoid ON and the voltage feedback remains high, B+.
Action Taken When the DTC Sets
| • | The transmission control module (TCM) requests the engine control module (ECM) to illuminate the malfunction indicator lamp (MIL). |
| • | The TCM commands third gear. |
| • | The TCM commands maximum line pressure. |
| • | The TCM freezes transmission adaptive functions. |
| • | At the time of the first failure, the TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information as a Failure Record. |
| • | At the time of the second failure, the ECM records the operating conditions when the Conditions for Setting the DTC are met. The ECM stores this information as a Freeze Frame. |
| • | The TCM stores DTC P0788 in TCM history during the second consecutive trip in which the Conditions for Setting the DTC are met. |
Conditions for Clearing the DTC
| • | The ECM turns OFF the MIL after the third consecutive drive trip in which the TCM does not send a MIL illumination request. |
| • | A scan tool can clear the DTC. |
| • | The TCM clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without a non-emission related diagnostic fault occurring. |
| • | The TCM cancels the default actions when the ignition is OFF long enough in order to power down the TCM. |
Step | Action | Values | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |||||||
2 |
Important: Before clearing the DTC, use the scan tool in order to record the Freeze Frame and Failure Records. Using the Clear Info function erases the Freeze Frame and Failure Records from the transmission control module (TCM). Does the 3-2 Sol. CKT status parameter display OK? | -- | Go to Testing for Intermittent Conditions and Poor Connections | Go to Step 3 | ||||||
3 |
Refer to Automatic Transmission Inline 20-Way Connector End View . Does the test lamp illuminate? | -- | Go to Step 6 | Go to Step 4 | ||||||
4 |
Refer to Automatic Transmission Inline 20-Way Connector End View . Does the resistance measure less than the specified value? | 20 ohms | Go to Step 5 | Go to Step 7 | ||||||
5 |
Does the resistance measure less than the specified value? | 20 ohms | Go to Step 8 | Go to Step 7 | ||||||
6 | Test the control circuit of the 3-2 SS valve for a short to voltage between the TCM and the AT inline 20-way connector. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 9 | ||||||
7 | Replace the AT internal wiring harness. Did you complete the replacement? | -- | Go to Step 10 | -- | ||||||
8 | Replace the 3-2 SS valve. Refer to Control and Shift Solenoids Replacement . Did you complete the replacement? | -- | Go to Step 10 | -- | ||||||
9 | Replace the TCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 10 | -- | ||||||
10 | Perform the following procedure in order to verify the repair:
Has the test run and passed? | -- | Go to Step 11 | Go to Step 2 | ||||||
11 | With the scan tool, observe the stored information, capture info, and DTC Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK |
DTC P0788 4.2L
Circuit Description
The 3-2 shift solenoid (SS) valve is a normally-closed, 3-port, ON/OFF device that controls the 3-2 downshift. The solenoid attaches to the control valve body within the transmission. The solenoid receives voltage through the ignition voltage circuit. The powertrain control module (PCM) controls the solenoid by providing a ground path on the 3-2 shift solenoid valve control circuit. During a 3-2 downshift, the 2-4 band applies as the 3-4 clutch releases. The PCM varies the timing between the 3-4 clutch release and the 2-4 band apply depending on the vehicle speed and throttle position.
When the PCM detects a continuous short to voltage in the 3-2 shift solenoid valve control circuit, then DTC P0788 sets. DTC P0788 is a type A DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0788 3-2 Shift Solenoid (SS) Control Circuit High Voltage
Conditions for Running the DTC
| • | The system voltage is 8-18 volts. |
| • | The engine speed is 475 RPM for 5 seconds. |
| • | Vehicle speed. |
Conditions for Setting the DTC
DTC P0788 sets if the PCM commands the solenoid ON and the voltage feedback remains high, B+.
Action Taken When the DTC Sets
| • | The powertrain control module (PCM) requests the engine control module (ECM) to illuminate the malfunction indicator lamp (MIL). |
| • | The PCM commands third gear. |
| • | The PCM commands maximum line pressure. |
| • | The PCM freezes transmission adaptive functions. |
| • | At the time of the first failure, the PCM records the operating conditions when the Conditions for Setting the DTC are met. The PCM stores this information as a Failure Record. |
| • | At the time of the second failure, the ECM records the operating conditions when the Conditions for Setting the DTC are met. The ECM stores this information as a Freeze Frame. |
| • | The PCM stores DTC P0788 in PCM history during the second consecutive trip in which the Conditions for Setting the DTC are met. |
Conditions for Clearing the DTC
| • | The engine control module (ECM) turns OFF the MIL after the third consecutive drive trip in which the PCM does not send a MIL illumination request. |
| • | A scan tool can clear the DTC. |
| • | The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without a non-emission related diagnostic fault occurring. |
| • | The PCM cancels the default actions when the ignition is OFF long enough in order to power down the PCM. |
Step | Action | Values | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |||||||
2 |
Important: Before clearing the DTC, use the scan tool in order to record the Freeze Frame and Failure Records. Using the Clear Info function erases the Freeze Frame and Failure Records from the powertrain control module (PCM). Does the 3-2 Sol. CKT status parameter display OK? | -- | Go to Testing for Intermittent Conditions and Poor Connections | Go to Step 3 | ||||||
3 |
Refer to Automatic Transmission Inline 20-Way Connector End View . Does the test lamp illuminate? | -- | Go to Step 6 | Go to Step 4 | ||||||
4 |
Refer to Automatic Transmission Inline 20-Way Connector End View . Does the resistance measure less than the specified value? | 20 ohms | Go to Step 5 | Go to Step 7 | ||||||
5 |
Does the resistance measure less than the specified value? | 20 ohms | Go to Step 8 | Go to Step 7 | ||||||
6 | Test the control circuit of the 3-2 SS valve for a short to voltage between the PCM and the AT inline 20-way connector. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 9 | ||||||
7 | Replace the AT internal wiring harness. Did you complete the replacement? | -- | Go to Step 10 | -- | ||||||
8 | Replace the 3-2 SS valve. Refer to Control and Shift Solenoids Replacement . Did you complete the replacement? | -- | Go to Step 10 | -- | ||||||
9 | Replace the PCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 10 | -- | ||||||
10 | Perform the following procedure in order to verify the repair:
Has the test run and passed? | -- | Go to Step 11 | Go to Step 2 | ||||||
11 | With the scan tool, observe the stored information, capture info, and DTC Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK |
