Circuit Description
The pressure control (PC) solenoid valve regulates actuator feed fluid passing through the solenoid into torque signal pressure. The TCM uses a pulse width modulated signal in order to control the torque signal pressure. The TCM compares various inputs in order to determine the appropriate pressure for a given load. The TCM varies the current to the PC solenoid from 0.1 amps, for maximum line pressure to 1.1 amps, for minimum line pressure. An internal current monitor within the TCM provides feedback in order to determine actual PC solenoid valve current draw.
If the TCM detects a continuous open or short to ground in the PC solenoid circuit, then DTC P0748 sets. DTC P0748 is a type C DTC.
Conditions for Running the DTC
The ignition voltage is 8-18 volts.
Conditions for Setting the DTC
The PC solenoid valve feedback circuit indicates a continuous open or short to ground for greater than 0.7 seconds.
Action Taken When the DTC Sets
| • | The TCM does not request the ECM to illuminate the malfunction indicator lamp (MIL). |
| • | SERVICE VEHICLE SOON displays on the driver information center (DIC). |
| • | The TCM turns off the pressure control solenoid. When the pressure control solenoid is off, line pressure is at maximum and updates to the transmission adaptive pressure (TAP) memory cells are discontinued. |
| • | The TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information as a Failure Record. |
| • | The TCM stores DTC P0748 in TCM history. |
Conditions for Clearing the DIC/DTC
| • | The TCM clears the DIC when the condition no longer exists. |
| • | 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 DTC default actions when the ignition 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 verifies the ability of the TCM to command the PC solenoid valve.
-
This step verifies that the automatic transmission wiring harness and the PC solenoid have correct resistance.
Step | Action | Value(s) | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Engine Controls? | -- | Go to Step 2 | Go to Diagnostic System Check - Engine Controls in Engine Controls - 2.6L and 3.2L | ||||
Important:
Does the PC Sol. Actual Current reading vary from the PC Sol. Ref. Current reading by more than the specified amount? | 0.05 amps | Go to Step 3 | Go to Intermittent Conditions in Engine Controls - 2.6L and 3.2L | |||||
Is the resistance within the specified range? | 3.5-5.5 ohms | Go to Step 7 | Go to Step 4 | |||||
4 | Is the resistance greater than the specified value? | 5.5 ohms | Go to Step 5 | Go to Step 6 | ||||
5 |
Refer to Testing for Continuity in Wiring Systems. Did you find a condition? | -- | Go to Step 18 | Go to Step 19 | ||||
6 | Test the high control circuit (CKT 1228) and the low control circuit (CKT 1229) of the PC solenoid for being shorted together between the AT inline 20-way connector and the PC solenoid. Refer to Circuit Testing in Wiring Systems. Did you find the condition? | -- | Go to Step 18 | Go to Step 19 | ||||
7 | Measure the resistance from terminal 13 of the jumper harness to ground. Is the resistance less than the specified value? | 10 ohms | Go to Step 8 | Go to Step 9 | ||||
8 |
Refer to Testing for Short to Ground in Wiring Systems. Did you find a condition? | -- | Go to Step 18 | Go to Step 19 | ||||
9 | Measure the resistance between terminal 13 and all other terminals, except terminal 8, of the J 45681 . Refer to Automatic Transmission Inline 20-Way Connector End View . Is the resistance between terminal 13 and any other terminal, except terminal 8, less than the specified value? | 100 ohms | Go to Step 18 | Go to Step 10 | ||||
10 |
Refer to Automatic Transmission Inline 20-Way Connector End View . Is the resistance less than the specified value? | 10 ohms | Go to Step 11 | Go to Step 12 | ||||
11 | Test the low control circuit (CKT 1229) of the PC solenoid for a short to ground between the TCM connector and the AT inline 20-way connector. Refer to Testing for Short to Ground in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 21 | -- | ||||
12 | Using the DMM and the J 35616 , measure the resistance between terminal 8 of the J 45681 and terminal 29 of the TCM connector. Refer to Automatic Transmission Inline 20-Way Connector End View . Is the resistance less than the specified value? | 10 ohms | Go to Step 14 | Go to Step 13 | ||||
13 | Test the low control circuit (CKT 1229) of the PC solenoid for an open between the TCM connector and the AT inline 20-way connector. Refer to Testing for Continuity in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 21 | -- | ||||
14 | Using the DMM and the J 35616 , measure the resistance from terminal 13 of the J 45681 to ground. Refer to Automatic Transmission Inline 20-Way Connector End View . Is the resistance less than the specified value? | 10 ohms | Go to Step 15 | Go to Step 16 | ||||
15 | Test the high control circuit (CKT 1228) of the PC solenoid for a short to ground between the TCM connector and the AT inline 20-way connector. Refer to Testing for Short to Ground in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 21 | -- | ||||
16 | Using the DMM and the J 35616 , measure the resistance between terminal 13 of the J 45681 and terminal 3 of the TCM connector. Refer to Automatic Transmission Inline 20-Way Connector End View . Is the resistance less than the specified value? | 10 ohms | Go to Step 20 | Go to Step 17 | ||||
17 | Test the high control circuit (CKT 1228) of the PC solenoid for an open between the TCM connector and the AT inline 20-way connector. Refer to Testing for Continuity in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 21 | -- | ||||
18 | Replace the automatic transmission wiring harness. Refer to Transmission Internal Electrical Harness Replacement . Is the action complete? | -- | Go to Step 21 | -- | ||||
19 | Replace the PC solenoid. Refer to Pressure Control Solenoid Valve Replacement . Is the action complete? | -- | Go to Step 21 | -- | ||||
20 | Replace the TCM. Refer to Transmission Control Module Replacement . Is the action complete? | -- | Go to Step 21 | -- | ||||
21 | Perform the following procedure in order to verify the repair:
Has the test run and passed? | -- | Go to Step 22 | Go to Step 2 | ||||
22 | 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? | -- | Go to Diagnostic Trouble Code (DTC) List in Engine Controls - 2.6L and 3.2L | System OK |
