Here are the diagnostic procedures for both codes.
DTC P0740/40: LOCK-UP CONTROL SYSTEM
1. Using scan tool, retrieve A/T freeze data. Clear DTCs and road test vehicle under same conditions freeze data was recorded. If DTC returns, go to next step. If DTC does not return, problem is intermittent. Check transaxle and PCM connections.
2. Using scan tool, check for any other DTCs. If any other DTCs are present, repair those DTCs first and recheck for DTC P0740/40. If no other DTCs are present, go to next step.
3. Measure clutch pressure at each clutch pressure tap on transaxle. If all clutch pressures are within specification, go to next step. If any clutch pressure is not within specification, repair hydraulic system as necessary.
4. Replace lock-up control solenoid assembly and A/T clutch pressure control solenoid valve "C". Turn ignition off and clear codes. Ensure engine coolant temperature is greater than 176°F (80°C). Road test vehicle at 55 MPH for more than one minute. Recheck DTCs. If DTC P0740/40 returns, replace transaxle and torque converter. If DTC P0740/40 does not return, system is okay.
DTC P0710/28: ATF TEMPERATURE SENSOR
1. Using scan tool, retrieve A/T freeze data. Clear DTCs and road test vehicle under same conditions freeze data was recorded. If DTC returns, go to next step. If DTC does not return, problem is intermittent.
2. Disconnect ATF temperature sensor connector. Measure resistance between sensor component connector terminals. If resistance is 50-2500 ohms, go to next step. If resistance is not 50-2500 ohms, replace ATF temperature sensor.
3. Turn ignition on. Measure voltage between ground and terminal No. 2 (Blue/Yellow wire) on ATF temperature sensor harness connector. If voltage is about 5 volts, go to next step. If voltage is not about 5 volts, go to step 5.
4. Measure voltage between terminals on ATF temperature sensor harness connector. If voltage is about 5 volts, inspect for loose PCM harness connectors. Repair as necessary. If no problem is found, replace PCM with a known-good unit and retest. If voltage is not about 5 volts, repair open in Blue/Yellow wire between ATF temperature sensor and PCM.
5. By backprobing PCM connector "C", measure voltage between ground and terminal No. 24. If voltage is about 5 volts, repair open in Blue/Yellow wire between PCM and ATF temperature sensor. If voltage is not about 5 volts, go to next step.
6. Turn ignition off. Disconnect PCM harness connector "C". Check continuity between ground and terminal No. 24 on PCM harness connector "C". If continuity exists, repair short to ground in Blue/Yellow wire between PCM and ATF temperature sensor. If continuity does not exist, inspect for loose PCM harness connectors. Repair as necessary. If no problem is found, replace PCM with a known-good unit and retest.
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Tuesday, January 18th, 2011 AT 12:44 PM