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The most common cause of the DTC (Diagnostic Trouble Code) PO750, is a defective shift solenoid, which is located in the Main Control Valve Body-Assembly, (FOR INSTRUCTIONS CLICK HERE).
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In order to properly diagnose you will a NGS (New Generation Star) scan tool or equivalent AND A dvom (DIGITAL VOLT OHM METER), see below. Hope this helps you out.
Pinpoint Test A - Shift Solenoid
P0781, P0782, P0783, P1731, P1732, P1733 - Shift errors.
P0750, P0755, P0760 - Solenoid circuit failures.
P0751, P1751 - Shift solenoid number 1 malfunction.
P0756, P1756 - Shift solenoid number 2 malfunction.
P0761, P1761 - Shift solenoid number 3 malfunction.
This pinpoint test is intended to diagnose the shift solenoids electrical system only. To prevent replacement of good components, be aware that the following areas may be at fault:
- Performance, cooling, brakes.
- Battery, input sensors, wiring harnesses.
- Internal transmission components, linkages, cooling.
This pinpoint test is intended to diagnose the following components:
- Transmission wiring harness, SS1, SS2, SS3.
- Powertrain control module.
Solenoid Operation Chart *
|Gearshift Lever Position||PCM Commanded Gear||Solenoids|
|(D)||3 (Below 26 km/h [16 mph])||OFF||OFF||OFF|
|(D)||3 (Above 26 km/h [16 mph])||ON||OFF||OFF|
|D||3 (Below 26 km/h [16 mph])||OFF||OFF||OFF|
|D||3 (Above 26 km/h [16 mph])||ON||OFF||OFF|
|L||2* (Below 110 km/h [68 mph])||ON||ON||OFF|
|L||2* (Above 110 km/h [68 mph])||ON||OFF||OFF|
Overspeed protection only.
PINPOINT TEST A: SHIFT SOLENOID
|A1 ELECTRONIC DIAGNOSTICS|
|Check to make sure the transmission harness connector is fully seated, terminals are engaged in connector and in good condition before proceeding.|
|CONNECT NGS |
|Diagnostic Data Link|
|Active Command Modes|
|Trigger the PCM active command OUTPUT TEST MODE ALL ON.|
Yes REMAIN in OUTPUT TEST MODE. GO to A2 .
- Does the vehicle enter OUTPUT TEST MODE?
No PRESS START. If the vehicle does not enter the OTM, REFER to Powertrain Control/Emissions Diagnosis (PC/ED) manual Manual Output Test Mode NOT FUNCTIONING in Section 5A, (Pinpoint Test MB).
|A2 CHECK THE ELECTRICAL SIGNAL OPERATION|
|NOTE: The 8-pin transmission connector refers to the connector at the base of the transmission.|
|DISCONNECT 8-Pin Transmission Connector||CAUTION: Do not pry on the connector. This will damage the connector and could result in a transmission concern. Pull up on the connector harness. |
Disconnect the 8-pin transmission connector.
|Use a mirror to inspect both ends of the connector for damage or pushed out pins, corrosion, loose wires and missing or damaged seals.|
|Measure the voltage between appropriate solenoid circuit at the 8-pin transmission connector, pin 3 (O/GN), pin 4 (LG/BL), or pin 8 (PK/BK), and ground.|
|While observing the Volt Ohm Meter, press start and stop to cycle solenoid output ON and OFF.|
Yes GO to A5.
- Does the suspect solenoid output voltage change at least 0.2 volts?
No GO to A3.
|A3 CHECK THE CONTINUITY OF THE SOLENOID SIGNAL CIRCUITS|
|DISCONNECT PCM C212||Inspect for damaged or pushed out pins, corrosion or loose wires.|
|Connect the EEC5 104 Pin Breakout Box and leave the PCM disconnected.|
|Measure the resistance of the appropriate solenoid circuit between the powertrain control module (PCM) signal test pin 1, 27, or 53 at the breakout box and the signal pin 3 (O/GN), pin 4 (LG/BL), or pin 8 (PK/BK) at the 8-pin transmission connector.|
Yes GO to A4.
- Is each resistance less than 5 ohms?
No REPAIR the open circuit(s). REMOVE the breakout box. RECONNECT all of the components. REPEAT the Quick Tests.
|A4 CHECK THE SOLENOID HARNESS FOR SHORT TO POWER AND GROUND|
|Measure the resistance of the appropriate solenoid circuit between the PCM signal output test pin 1, 27, or 53 and test pins 71 and 97 at the breakout box.|
|Measure the resistance of the appropriate solenoid circuit between the PCM signal output test pin 1, 27, or 53 and test pins 51 and 91 at the breakout box, and ground.|
Yes REPLACE PCM; TEST the vehicle for normal operation.
- Are the resistances greater than 10,000 ohms?
No REPAIR the short circuit(s). REMOVE the breakout box. RECONNECT all of the components. REPEAT the Quick Tests.
|A5 CHECK THE RESISTANCE OF THE SOLENOID/HARNESS|
RECONNECT 8-Pin Transmission Connector
|DISCONNECT Transmission C191|
|Measure the resistance of the appropriate solenoid circuit between the transmission C191F-3 (BK/BR), C191F-4 (PK/BL), and C191F-8 (GY/BK), and ground.|
|Record the resistance. The resistance should be between 12 and 20 ohms.|
Yes GO to Diagnosis By Symptom. REPAIR or REPLACE as necessary.
- Is the resistance for each solenoid between 12 and 20 ohms?
No REPLACE the main control valve body.
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