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 valve. The solenoid is a normally-open exhaust valve. The combination of the 2-3 Shift Solenoid Valve (2-3 SS Valve) and the 1-2 SS Valve allows four different shifting combinations. The solenoid attaches to the control valve body within the transmission. Circuit 639 supplies ignition voltage directly to the 1-2 SS Valve. The PCM controls the solenoid by providing a ground path through circuit 1222.

When the PCM detects a continuous open or a 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 DTC.

CONDITIONS FOR SETTING THE DTC

^ The ignition is ON.
^ The system voltage is 10-16 volts.
^ The PCM commands the solenoid ON and voltage remains high (B+).
^ The PCM commands the solenoid OFF, and the voltage remains low (0 volts).
^ All conditions are met for 5 seconds.

ACTION TAKEN WHEN THE DTC SETS

^ The PCM commands maximum line pressure.
^ The PCM disables shift adapts.
^ The PCM inhibits downshifts to 2nd gear if the vehicle speed is greater than 48 km/h (30 mph).
^ The PCM illuminates the Malfunction Indicator Lamp (MIL).

CONDITIONS FOR CLEARING THE MIL/DTC

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

DIAGNOSTIC AIDS

^ Inspect the wiring for poor electrical connections at the PCM. 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.
^ Refer to Shift Solenoid Valve State and Gear Ratio table.

TEST DESCRIPTION

6. This step isolates the fault between the engine harness and the transmission harness.
8. This step verifies that circuit 1222 is neither open nor shorted to power.
12. This step verifies that the 1-2 shift solenoid has neither shorted across its windings nor increased its resistance.
19. Because of the harsh conditions inside the transmission, repairing the A/T Wiring Harness is not acceptable. You must replace the A/T Wiring Harness.