Circuit Description
The 1-2 shift solenoid (SS) valve controls transmission fluid pressure acting on the 1-2 and 3-4 shift valves to position the valves for the appropriate gear. The 1-2 SS valve is a normally open exhaust valve located on the lower control valve body. Ignition 1 voltage is supplied to the solenoid. The transmission control module (TCM) commands the solenoid ON or OFF by providing a ground path. When the 1-2 SS valve is commanded ON, the TCM senses low voltage. When the 1-2 SS valve is commanded OFF, the TCM senses high voltage.
If the TCM detects a continuous short to voltage in the 1-2 SS valve circuit, then DTC P0974 sets. DTC P0974 is a type B DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0974 1-2 Shift Solenoid (SS) Control Circuit High Voltage
Conditions for Running the DTC
| • | The engine run time is greater than 5 seconds. |
| • | The TCM commands the 1-2 SS valve ON. |
Conditions for Setting the DTC
The TCM detects a short to voltage in the 1-2 SS valve circuit for 4.4 seconds.
Action Taken When the DTC Sets
| • | The TCM requests the engine control module (ECM) to illuminate the malfunction indicator lamp (MIL) during the second consecutive trip in which the Conditions for Setting the DTC are met. |
| • | The TCM commands maximum line pressure. |
| • | The TCM freezes transmission adaptive functions. |
| • | The ECM records the operating conditions when the Conditions for Setting the DTC are met. The ECM stores this information as Freeze Frame and Failure Records. |
| • | The TCM stores DTC P0974 in TCM history during the second consecutive trip in which the Conditions for Setting the DTC are met. |
Conditions for Clearing the MIL/DTC
| • | The ECM turns OFF the MIL after the third consecutive drive trip in which the TCM does not send a MIL illumination request. |
| • | The TCM clears the DIC message when the condition no longer exists. |
| • | A scan tool can clear the MIL/DTC. |
| • | The TCM clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring. |
| • | The TCM cancels the DTC default actions when the ignition switch is OFF long enough in order to power down the TCM. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step tests the TCM and the wiring to the transmission.
-
This step verifies that the circuit has the correct resistance.
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 TCM. Does the scan tool display indicate a short to voltage? | -- | Go to Step 3 | Go to Testing for Intermittent Conditions and Poor Connections |
Refer to Automatic Transmission Inline 20-Way Connector End View . Is the test lamp ON? | -- | Go to Step 4 | Go to Step 5 | |
4 | Test the control circuit of the 1-2 SS valve for a short to voltage between the TCM connector and the AT inline 20-way connector. Refer to Testing for a Short to Voltage and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 10 |
Refer to Automatic Transmission Inline 20-Way Connector End View . Does the resistance measure within the specified range? | 20-50 ohms | Go to Step 7 | Go to Step 6 | |
6 |
Does the resistance measure less than the specified value? | 250 K ohms | Go to Step 8 | Go to Step 9 |
7 | Measure the resistance between terminal A and all other terminals, except terminals B and E, of the J 44152 . Refer to Automatic Transmission Inline 20-Way Connector End View . Does the resistance measure between terminal A and any other terminal, except terminals B and E, less than the specified value? | 250 K ohms | Go to Step 8 | Go to Testing for Intermittent Conditions and Poor Connections |
8 |
Important: The automatic transmission wiring harness consists of two separate harnesses, the Automatic Transmission Wiring Harness Assembly and the Automatic Transmission Wiring Extension Harness Assembly. In order to avoid the unnecessary replacement of parts, determine which harness contains the fault and replace only that harness. Replace the automatic transmission wiring harness. Refer to Input Speed Sensor and Wiring Harness Removal in the 4T80-E section of the Transmission Unit Repair Manual. Did you complete the replacement? | -- | Go to Step 11 | -- |
9 | Replace the 1-2 SS valve. Refer to Control Valve Lower Body Disassemble in the 4T80-E section of the Transmission Unit Repair Manual. Did you complete the replacement? | -- | Go to Step 11 | -- |
10 | Replace the TCM. Refer to Control Module References . Did you complete the replacement? | -- | Go to Step 11 | -- |
11 | Perform the following procedure in order to verify the repair:
Has the test run and passed? | -- | Go to Step 12 | Go to Step 2 |
12 | 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 |
