P0753

CIRCUIT DESCRIPTION
The 1-2 Shift Solenoid Valve (1-2 SS Valve) controls the fluid flow acting on the 1-2 and 3-4 shift valves. The solenoid is a normally-open exhaust valve. With the 2-3 Shift Solenoid Valve (2-3 SS Valve), the 1-2 SS Valve allows four different shifting combinations.

The solenoid attaches to the control valve body within the transmission. The 1-2 SS Valve receives ignition voltage through circuit 1020. The VCM controls the solenoid by providing the ground path on circuit 1222.

When the VCM detects a continuous open or short to ground in the 1-2 SS Valve circuit or the 1-2 SS Valve, then DTC P0753 sets. DTC P0753 is a type A DTC.

CONDITIONS FOR SETTING THE DTC
^ The system voltage is 10-17 volts.
^ The engine is running.
^ All of the above conditions are met for 5 seconds and either of the following fail conditions occurs for 5 seconds:

- The VCM commands the solenoid ON and the voltage remains high (B+).
- The VCM commands the solenoid OFF and the voltage remains low (0 volts).

ACTION TAKEN WHEN THE DTC SETS
^ The VCM commands maximum line pressure.
^ The VCM freezes shift adapts from being updated.
^ If in hot mode, the TCC engages in 3rd or 4th gear if there is no braking. If in hot mode, the TCC engages in 3rd or 4th gear if there are no downshifts.
^ The VCM inhibits downshifts to 2nd gear over 48 km/h (30 mph).
^ The VCM illuminates the Malfunction Indicator Lamp (MIL).

CONDITIONS FOR CLEARING THE MIL/DTC
^ The VCM turns OFF the MIL after three consecutive ignition cycles without a failure reported.
^ A scan tool can clear the DTC from the VCM history. The VCM clears the DTC from the VCM history if the vehicle completes 40 warm-up cycles without a failure reported.
^ The VCM cancels the DTC default actions when the fault no longer exists and the ignition is OFF long enough in order to power down the VCM.

DIAGNOSTIC AIDS
^ Inspect the wiring for poor electrical connections at the VCM. Inspect the wiring for poor electrical connections at the transmission 20-way connector. Look for the following conditions:

- A bent terminal.
- A backed out terminal.
- A damaged terminal.
- Poor terminal tension.
- A chafed wire.
- A broken wire inside the insulation.

^ When diagnosing for an intermittent short or open condition, massage the wiring harness while watching the test equipment for a change.
^ An open ignition feed circuit can cause multiple DTCs to set.

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic chart.

4. This Step tests the function of the 1-2 SS Valve and the Automatic Transmission Wiring Harness Assembly.
5. This Step tests for power to the 1-2 SS Valve from the ignition through the fuse.
7. This Step tests circuit 1222 from the transmission 20-way connector to the VCM for an open.
8. This Step tests circuit 1222 from the transmission 20-way connector to the VCM for a short to ground.