P0753

Circuit Description
The 1-2, 3-4 shift solenoid (1-2, 3-4 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 3-4 SS valve is a normally-open exhaust valve located on the control valve body. Circuit 1039/839 supplies ignition voltage to the 1-2, 3-4 SS valve. The output driver module, within the PCM, commands the solenoid ON or OFF by providing a ground path through circuit 1222. When the 1-2, 3-4 SS valve is commanded ON, the PCM senses low voltage. When the 1-2, 3-4 SS valve is commanded OFF, the PCM senses high voltage. If the PCM detects a continuous open or a short to ground in circuit 1222 or the 1-2, 3-4 SS valve, then DTC P0753 sets. DTC P0753 is a type B DTC.

Conditions for Running the DTC
^ The system voltage is 9-18 volts.
^ The engine speed is greater than 500 RPM for 5 seconds and not in fuel shut off.

Conditions for Setting the DTC
DTC P0753 sets when either of the following conditions occurs for 5 seconds:
^ The PCM commands the solenoid ON and voltage remains high (B+).
^ The PCM commands the solenoid OFF, and the voltage remains low (0 volts).

Action Taken When the DTC Sets
^ The PCM illuminates the malfunction indicator lamp (MIL) during the second consecutive trip in which the conditions for setting the DTC are met.
^ The PCM commands maximum line pressure.
^ The PCM freezes shift adapts.
^ The PCM inhibits 3-2 downshifts when the vehicle speed is greater than 48 km/h (30 mph).
^ The PCM stores DTC P0753 in PCM history.

Conditions for Clearing the MIL/DTC
^ The PCM turns OFF the MIL during the third consecutive trip in which the diagnostic test runs and passes.
^ A scan tool clears the DTC from the PCM history.
^ The PCM clears the DTC from the PCM history if the vehicle completes 40 consecutive warm-up cycles without an emission related diagnostic fault occurring.
^ The PCM cancels the DTC default actions when the fault no longer exists and the ignition switch is OFF long enough in order to power down the PCM.

Diagnostic Aids
^ Inspect the wiring at the PCM, the transmission 20-way connector, the 1-2, 3-4 SS valve connector and all Other circuit connecting points for the following conditions:
- A backed out terminal
- A damaged terminal
- Reduced terminal tension
- A chafed wire
- A broken wire inside the insulation
- Moisture intrusion
- Corrosion
^ When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change.
^ Ensure that the scan tool commanded gear has correct solenoid states and ratio.

Test Description
The numbers below refer to the step numbers on the diagnostic table.
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.
10. This step verifies that the 1-2, 3-4 shift solenoid (SS) valve has neither shorted across its windings nor increased its resistance.
17. Because of the harsh conditions inside the transmission, repairing the automatic transmission (A/T) wiring harness assembly is not acceptable. You must replace the A/T wiring harness assembly.