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.
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 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 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 problems: |
| - | 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, massage the wiring harness while watching the test equipment for a change. |
| • | Refer to Shift Solenoid Valve State and Gear Ratio table. |
Test Description
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This step isolates the fault between the engine harness and the transmission harness.
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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.
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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? | -- | ||||||||||||||
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 problem? | -- | ||||||||||||||
4 | Repair short to ground in circuit 639. Refer to Troubleshooting Procedures, Section 8. Did you find and correct a problem? | -- | -- | |||||||||||||
5 | Repair the open in circuit 639. Refer to Troubleshooting Procedures, Section 8. Did you find and correct a problem? | -- | -- | |||||||||||||
Important: Additional DTCs will set. Is the test lamp ON? | -- | |||||||||||||||
7 | Inspect circuit 1222 for a short to ground. Refer to Troubleshooting Procedures, Section 8. Did you find and correct a problem? | -- | ||||||||||||||
Does the test lamp cycle ON and OFF as commanded? | -- | |||||||||||||||
9 | Inspect circuit 1222 for an open. Refer to Troubleshooting Procedures, Section 8. Did you find and correct a problem? | -- | ||||||||||||||
10 | Is the test lamp always OFF? | -- | -- | |||||||||||||
11 | Inspect circuit 1222 for a short to power. Refer to Troubleshooting Procedures, Section 8. Did you find and correct a problem? | -- | ||||||||||||||
Is the measured resistance within the specified range? | 19-24ohms at 20°C (68°F) 24-31ohms at 88°C (190°F) | |||||||||||||||
13 | Is the resistance greater than the specified value? | 100ohms | ||||||||||||||
14 |
Refer to Troubleshooting Procedures, Section 8. Did you find a problem? | -- | ||||||||||||||
15 | Connect the ohmmeter from terminal A of the jumper to ground. Is the resistance less than the specified value? | 100ohms | ||||||||||||||
16 | Inspect Automatic Transmission (A/T) Wiring Harness circuit 1222 (LT GRN) for a short to ground. Refer to Troubleshooting Procedures, Section 8. Did you find and correct a problem? | -- | -- | |||||||||||||
17 | Replace the 1-2 Shift Solenoid. Refer to Solenoids and Wiring Harness, in On-Vehicle Service. Is the replacement complete? | -- | -- | |||||||||||||
18 | Replace the PCM. Refer to Powertrain Control Module Replacement/Programming , Section 6. Is the replacement complete? | -- | -- | |||||||||||||
Replace the A/T Wiring Harness. Refer to Solenoids and Wiring Harness, in On-Vehicle Service. Is the replacement complete? | -- | -- | ||||||||||||||
20 | In order to verify your repair, perform the following procedure:
Has the test run and passed? | -- | System OK |
