1998 Pontiac Grand Prix DTC P0753 1-2 Shift Solenoid Circuit Electrical 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 1339/839 supplies 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 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 20-way connector, the 1-2 Shift Solenoid Valve 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 the Shift Solenoid Valve State and Gear Ratio table. 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. 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 Automatic Transmission Wiring Harness Assembly is not acceptable. You must replace the Automatic Transmission Wiring Harness Assembly. DTC P0753 1-2 Shift Solenoid Circuit Electrical Step Action Value(s) Yes No 1 Was the Powertrain On-Board Diagnostic (OBD) System Check performed? 1. Install the Scan Tool. 2. With the engine OFF, turn the ignition switch to the RUN position. Important Step 2 Powertrain On Board Diagnostic (OBD) System Check in Engine Controls
2 Before clearing the DTC(s), use the Scan Tool in order to record the Freeze Frame and Failure Records for reference. Using the Clear Info function will erase the stored Freeze Frame and Failure Records from the PCM. 3. Record the DTC Freeze Frame and Failure Records, then clear the DTC(s). Are DTCs P0758 and P1860 set? Step 3 Step 6 3 1. Remove the TCC fuse. 2. Inspect the fuse for an open. Step 4 Step 5 Repair short to ground in circuits 1339/839. 4 Refer to Wiring Repairs in Wiring Repair the open in circuits 1339/839. 5 Refer to Wiring Repairs in Wiring 1. Turn the ignition switch OFF. 2. Disconnect the transmission 20-way connector. 3. Connect the J 39775 Jumper Harness to the engine harness connector. 4. Connect a test lamp from terminal E to terminal A of the jumper harness. 6 Important Additional DTCs will set. 5. With the engine OFF, turn the ignition ON. Is the test lamp ON? Step 7 Step 8 Inspect circuit 1222 (LT GRN) for a short to ground. 7 Step 18 8 1. Using the Scan Tool, select A/T Outputs, 1-2 Solenoid. 2. Cycle the 1-2 solenoid ON and OFF three times. Does the test lamp cycle ON and OFF as commanded? Step 12 Step 9 Inspect circuit 1222 (LT GRN) for an open. 9
10 Step 10 Is the test lamp always OFF? Inspect circuit 1222 (LT GRN) for a short to power. Step 11 11 12 13 14 15 1. Turn the ignition OFF. 2. Disconnect the J 39775 Jumper Harness from the engine harness. 3. Connect the J 39775 Jumper Harness to the transmission 20-way connector. Refer to Automatic Transmission Inline Harness Connector End View. 4. Connect a Digital Multimeter (DMM), set to measure ohms, from terminal E to terminal A of the jumper harness. Is the measured resistance within the specified range? Is the resistance greater than the specified value? 1. Inspect automatic transmission wiring harness assembly circuit 839 (RED) for an open or a poor connection. 2. Inspect circuit 1222 (LT GRN) for an open or a poor connection. Did you find a condition? Connect the DMM from terminal A of the jumper to ground. Is the resistance less than the specified value? Inspect automatic transmission wiring harness assembly circuit 1222 (LT GRN) for a short to ground. 19-24 ohms at 20 C (68 F) 24-31 ohms at 88 C (190 F) 100 ohms Step 18 Step 15 Step 13 Step 14 Step 15 Step 19 Step 17 100 ohms Step 16 Step 17 16 Step 19 Replace the 1-2 Shift Solenoid. 17 Refer to 1-2 Shift Solenoid Valve Replacement. Replace the PCM. 18 Refer to PCM Replacement/Programming in Engine Controls. Replace the Automatic Transmission Wiring Harness
Assembly. 19 Refer to Solenoids and Wiring Harness Replacement. In order to verify your repair, perform the following procedure: 20 1. Select DTC. 2. Select Clear Info, then clear the DTC(s). 3. Operate the vehicle under the following conditions: The system voltage is 9-16 volts. The ignition switch is ON. The engine speed is more than 500 RPM for more than 5 seconds. The vehicle is not in fuel shut off. Drive the vehicle through a 1-2 shift cycle. No open or short to ground exists for more than 5 seconds in each solenoid state. 4. Select Specific DTC. 5. Enter DTC P0753. Has the test run and passed? System OK Step 1