Circuit Description
The 1-2 shift solenoid (SS) valve is located in the control valve body of the transmission. The transmission control module (TCM) selects the required gear by turning the appropriate shift solenoid on or off, enabling the transmission to shift. Refer to Shift Solenoid Valve State and Gear Ratio chart in Shift Solenoid Valve State and Gear Ratio.
The TCM provides voltage to the solenoid through the high side drive 2 (HSD2). The TCM uses a second driver to control the solenoid ground circuit. The controlled ground driver reports feedback voltage to the TCM. When the TCM commands the 1-2 shift solenoid valve on, the voltage of the control circuit should be approximately 0 volts. When the TCM commands the 1-2 shift solenoid valve off, the voltage of the control circuit should be approximately system voltage.
When the TCM detects a continuous open or short to ground in the 1-2 shift solenoid valve circuit, then DTC P0973 sets, which is a type 'B' DTC.
Conditions for Running the DTC
| • | Ignition voltage is between 8-18 volts. |
| • | Engine speed is between 450-6,800 RPM for at least 5 seconds. |
| • | The HSD2 is commanded on. |
Conditions for Setting the DTC
DTC P0973 sets when either of the following two conditions occur:
| • | The TCM detects an open in the 1-2 shift solenoid valve circuit when the HSD2 is commanded ON. |
| • | The TCM detects a short to ground in the 1-2 shift solenoid valve circuit when the HSD2 is commanded OFF. |
Action Taken When the DTC Sets
| • | Powertrain braking is disabled at the time that the TCM first detects the failure, before the DTC sets. |
| • | The TCM requests the powertrain interface module (PIM) to illuminate the check powertrain malfunction indicator lamp (MIL) in the instrument cluster during the second consecutive drive trip in which the 'Conditions for Setting the DTC' are met. |
| • | The TCM turns off power to all solenoids. When the solenoids are off: |
| - | The transmission will operate in fifth gear if the vehicle has successfully complete a 1-2 upshift in the current ignition cycle. If the vehicle has not completed a 1-2 shift in the current ignition cycle, the transmission will operate in fourth gear. If the transmission is operating in fifth gear, fourth gear may be obtained if the engine is stopped briefly and started again. |
| - | Line pressure is at maximum. |
| - | Torque converter clutch is disabled. |
| • | The TCM freezes the transmission adaptive learning function. |
| • | At the time of the first failure, the TCM records the operating conditions when the 'Conditions for Setting the DTC' have been 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' have been met. The ECM stores this information as a freeze frame. |
| • | The TCM stores DTC P0973 into TCM history. |
Conditions for Clearing the MIL/DTC
| • | Tech 2 can clear the DTC. |
| • | The TCM clears the DTC from its memory (history DTC) if the vehicle completes 40 warm-up cycles without a non-emission related DTC occurring. |
| • | The TCM cancels the default actions when the ignition is off long enough to power down the TCM. |
| • | The PIM turns off the check powertrain MIL after the sixth consecutive drive tip in which the TCM does not send a check powertrain MIL illumination request. |
Test Description
The following numbers refer to the step numbers on the diagnostic table.
-
Checks for short to ground or open circuit in solenoid supply circuit.
-
Checks for short to voltage on the solenoid supply circuit.
-
Checks for short to ground on the solenoid supply circuit.
-
Checks for open circuit in transmission internal wiring harness.
Step | Action | Values | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
Schematic Reference: Automatic Transmission Controls Schematics For information on testing wiring faults, refer to Wiring Systems. | ||||||||
1 | Has the Diagnostic System Check - Automatic Transmission been completed? | -- | Go to Step 2 | |||||
2 |
Does the solenoid operate? | -- | Go to Step 10 | Go to Step 3 | ||||
3 |
Does the test light illuminate? | -- | Go to Step 4 | Go to Step 8 | ||||
Is resistance reading within the specified value? | 15-20.3 Ω | Go to Step 5 | Go to Step 9 | |||||
Using a digital ohmmeter, measure resistance between terminal 17 of the transmission 20-way connector, X121-X1a and ground. Is resistance greater than the specified value? | More than 50 kΩ | Go to Step 6 | Go to Step 9 | |||||
Did you find an open circuit condition? | -- | Repair open in circuit 1222. Go to Step 13 | Go to Step 7 | |||||
Using a digital ohmmeter, check circuit 1222 between the transmission wiring harness TCM connector A112-T68, terminal X1-30 and the transmission wiring harness connector X121-X1, terminal X1-14 for a short to ground condition. Did you find an open circuit condition? | -- | Repair short to ground in circuit 1222. Go to Step 13 | Go to Step 10 | |||||
8 |
Did you find an open circuit condition? | -- | Repair open in circuit 1525. Go to Step 13 | Go to Step 10 | ||||
9 |
Did you find and correct a condition? | -- | Go to Step 11 | Go to Step 12 | ||||
10 | Replace the TCM. Refer to Transmission Control Module Replacement for replacement procedures. Is the replacement complete? | -- | Go to Step 13 | -- | ||||
11 | Remove and replace transmission internal wiring harness. Refer to Transmission Internal Electrical Harness Replacement for replacement procedures. Is the replacement complete? | -- | Go to Step 13 | -- | ||||
12 | Remove and replace the 1-2 shift solenoid valve. Refer to 1-2 Shift Solenoid Valve Replacement. Is the replacement complete? | -- | Go to Step 13 | -- | ||||
13 |
Has the test run and passed? | -- | System OK | Go to Step 2 | ||||
When all diagnosis and repairs are completed, clear all DTCs and verify correct operation. | ||||||||
