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. Circuits 239 and 839 supply ignition voltage to the 1-2 SS Valve. The PCM controls the solenoid by providing a ground path through circuit 1222.
If 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 A DTC.
Conditions for Setting the DTC
| • | The ignition is ON. |
| • | The system voltage is 9-16 volts. |
| • | The engine speed is greater than 500 RPM for 5 seconds, and not in fuel shut off. |
| • | 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 illuminates the Malfunction Indicator Lamp (MIL). |
| • | 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). |
Conditions for Clearing the MIL/DTC
| • | The PCM turns OFF the MIL after three consecutive trips 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 at the PCM, the transmission connector, 1-2 shift solenoid connector and all other circuit connecting points 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 |
| - | 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. Refer to Shift Solenoid Valve State and Gear Ratio . |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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This step isolates the fault between the engine harness and the transmission harness.
-
This step verifies that circuit 1222 is neither open nor shorted to power.
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This step verifies that the 1-2 shift solenoid has neither shorted across its windings nor increased its resistance.
-
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.
Step | Action | Value(s) | Yes | No | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Powertrain On Board Diagnostic (OBD) System Check in Engine Controls | |||||||||||||
2 |
Important: Before clearing the DTCs, use the Scan Tool in order to record the Freeze Frame and Failure Records for reference. The Clear Info function will erase the data. Are DTCs P0758 and P1860 set? | -- | ||||||||||||||
3 |
Did you find and correct a condition? | -- | ||||||||||||||
4 | Repair short to ground in circuits 239/839. Refer to Wiring Repairs in Wiring Systems. Did you find and correct a condition? | -- | -- | |||||||||||||
5 | Repair the open in circuits 239/839. Refer to Wiring Repairs in Wiring Systems. Did you find and correct a condition? | -- | -- | |||||||||||||
Refer to Automatic Transmission Inline Harness Connector End View . Important: Additional DTCs will set. Is the test lamp ON? | -- | |||||||||||||||
7 | Inspect circuit 1222 (LT GRN) for a short to ground. Refer to General Electrical Diagnosis in Wiring Systems. Did you find and correct a condition? | -- | ||||||||||||||
Does the test lamp cycle ON and OFF as commanded? | -- | |||||||||||||||
9 | Inspect circuit 1222 (LT GRN) for an open. Refer to General Electrical Diagnosis in Wiring Systems. Did you find and correct a condition? | -- | ||||||||||||||
10 | Is the test lamp always OFF? | -- | -- | |||||||||||||
11 | Inspect circuit 1222 (LT GRN) for a short to power. Refer to General Electrical Diagnosis in Wiring Systems. Did you find and correct a condition? | -- | ||||||||||||||
Refer to Automatic Transmission Inline Harness Connector End View . Is the measured resistance within the specified range? | 19-24 ohms at 20°C (68°F) 24-31 ohms at 88°C (190°F) | |||||||||||||||
13 | Is the resistance greater than the specified value? | 100 ohms | ||||||||||||||
14 |
Refer to General Electrical Diagnosis in Wiring Systems. Did you find a condition? | -- | ||||||||||||||
15 | Connect the J 39200 DMM from terminal A of the J 39775 jumper harness to ground. Refer to Automatic Transmission Inline Harness Connector End View . Is the resistance less than the specified value? | 100 ohms | ||||||||||||||
16 | Inspect automatic transmission wiring harness circuit 1222 (LT GRN) for a short to ground. Refer to General Electrical Diagnosis in Wiring Systems. Did you find and correct a condition? | -- | -- | |||||||||||||
17 | Replace the 1-2 Shift Solenoid. Refer to 1-2 Shift Solenoid Valve Replacement . Is the replacement complete? | -- | -- | |||||||||||||
18 | Replace the PCM. Refer to Powertrain Control Module Replacement/Programming in Engine Controls. Is the replacement complete? | -- | -- | |||||||||||||
Replace the automatic transmission wiring harness. Refer to Solenoids and Wiring Harness Replacement . Is the replacement complete? | -- | -- | ||||||||||||||
20 | In order to verify your repair, perform the following procedure:
Has the test run and passed? | -- | System OK |
