Diagnosis

1. With a DRB III(R) scan tool, verify that the MIL is caused by DTC P1740 - TCC or O/D Solenoid Performance.

2. If the MIL is due to DTC P1740, then with the DRB III(R), proceed to build a Custom Display. The Custom Display that is created will be used to monitor the engine speed input to the transmission and the transmission output speed when the torque converter clutch engagement occurs.

3. The Custom Display should include the following sensors and input/output displays:

a. PCM Engine RPM (found in the Sensors Menu)
b. Output Shaft Speed (found in the Sensors Menu)
C. Desired TC Clutch (found in the Inputs/Outputs Menu)
d. APP Pedal Position Volts (found in the Sensors Menu)
e. O/D Off Lamp (found in the Inputs/Outputs Menu)
f. Brake Switch (found in the Inputs/Outputs Menu)
g. Park/Neutral (found in the Inputs/Outputs Menu)

4. Save the Custom Display for use during the road test portion of the diagnosis.

ROAD TEST:

1. Start the engine.

2. With the DRB III(R), bring up the Custom Display that was created for this condition.

3. Make certain that the engine and transmission are at normal operating temperatures.

4. Press the O/D button on the shifter handle. This will prevent O/D engagement.

5. Verify on the Custom Display that the O/D Off Lamp display reads "ON / 3-SPEED".

6. Observe the APP Pedal Position Volts. Record the voltage value when the throttle is closed and the engine is at idle. This value is required to calculate how wide open the throttle must be when verifying TCC lock-up during the diagnostic road test.

When the diagnostic test is actually performed, the closed throttle (at idle) APP Pedal Position voltage must be added to the initial minimum and maximum test range voltages. The initial test range voltages are 0.6 volts (mm.) and 0.9 volts (max.). Add the at idle closed throttle voltage from Step 6, to each of the initial test range voltages to obtain the actual test range voltages.

An example: if the APP Pedal Position Voltage at closed throttle (and engine idling) is 0.5 volts, then add this reading (0.5 volts) to the initial test range voltages (0.6 volts and 0.9 volts) to obtain the actual diagnostic test range voltages of 1.1 volts and 1.4 volts respectively. In this example, the technician would accelerate the vehicle while maintaining an APP Pedal Position Voltage of between 1.1 volts (mm.) and 1.4 volts (max.).

7. Add the APP Pedal Position voltage obtained in Step 6, to the initial test range voltages (0.6 volts and 0.9 volts) to obtain the actual diagnostic test range voltages.

8. Accelerate the vehicle while maintaining the APP Pedal Position Voltage within the actual diagnostic test range (as calculated in step 7).

NOTE:
THE VEHICLE MUST BE DRIVEN IN A SAFE AREA AND IN A SAFE MANNER WHILE PERFORMING THE FOLLOWING DIAGNOSTIC TEST. OBSERVE ALL SPEED LIMITS.

9. Verify that the Brake Switch is "Released", and that the Park/Neutral reads "D/R".

10. Verify that the torque converter clutch command is being given. The Desired TC Clutch must read "LOCKED" within a few seconds of reaching 3rd gear.

11. Bring the vehicle to a stop with engine idling. Accelerate the vehicle while maintaining the APP Pedal Position voltage within the actual diagnostic test range voltages that were calculated in Step 7.

12. Continue to accelerate the vehicle through the 1-2 upshift and into the 2-3 upshift. Again, make certain that the O/D Off Lamp reads "ON /3-SPEED".

13. Monitor the Desired TC Clutch, the PCM Engine RPM, and the Output Shaft Speed values/readings as the transmission upshifts from 2nd to 3rd.

14. The PCM Engine RPM and the Output Shaft Speed values should be within +/- 30 rpm of each other within 6 seconds following the command from the PCM to lockup the torque converter clutch (Desired TC Clutch reads "LOCKED").

15. It may take three or four accelerations (Steps 11 through 14) to obtain a good diagnostic conclusion.

16. If the rpm difference between the PCM Engine RPM value/reading and the Output Shaft Speed value/reading is greater than +/- 30 rpm after 6 seconds following TCC lock-up in 3rd gear, then perform the Repair Procedure. If the difference before 6 seconds is less than +/- 30 rpm, then further diagnosis is required.