Circuit Description
The transmission control module (TCM) calculates gear ratio based on data from the automatic transmission input shaft speed (AT ISS) and automatic transmission output shaft speed (AT OSS) sensors. The TCM compares the calculated gear ratio to the known gear ratio for each commanded gear.
If the TCM detects an incorrect 1st gear ratio while decelerating in LOW (L), indicating no engine braking within the transmission, then DTC P0730 sets. DTC P0730 is a type A DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0730 Incorrect Gear Ratio
Conditions for Running the DTC
| • | No TR switch DTC P0705. |
| • | No TFT DTCs P0711, P0712, or P0713. |
| • | No ISS DTC P0717. |
| • | No OSS DTC P0722. |
| • | No engine speed DTC P0727. |
| • | No TCC DTC P0741. |
| • | No solenoid DTCs P0962, P0963, P0966, P0967, P0970, P0971, P0973, P0974, P0976, P0977, P0979, P0980, P0982, P0983, P0985, or P0986. |
| • | No engine torque DTC P1781. |
| • | No throttle position DTC P1791. |
| • | The ignition voltage is 10.5-18 volts. |
| • | The transmission temperature is greater than 20°C (68°F). |
| • | The transmission is in the LOW (L) range. |
| • | The elapsed time since the most recent range change is 8 seconds or greater. |
| • | The throttle position (TP) is 0 percent. |
| • | The engine speed is at least 400 RPM. |
| • | The commanded gear has been 1st for 0.5 seconds or greater. |
| • | The transmission output shaft speed (OSS) is 500-1260 RPM. |
Conditions for Setting the DTC
The TCM commands 1st gear with engine braking and the actual gear ratio is not within 3.68:1-5.52:1 while decelerating for 12 seconds.
Action Taken When the DTC Sets
| • | The TCM requests the powertrain control module (PCM) to illuminate the malfunction indicator lamp (MIL). |
| • | The TCM turns the Trans. Protection Mode ON. When the Trans. Protection Mode is ON, the following conditions occur: |
| - | The transmission will operate in 5th gear when the transmission is shifted into D or I range and 2nd gear when shifted into L range. |
| - | The line pressure is at maximum. |
| - | The torque converter clutch (TCC) is disabled. |
| - | The TCM freezes the transmission adaptive functions. |
| • | The TCM requests the PCM to limit engine torque to 150 N·m (111 lb ft). |
| • | The TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information as a Failure Record. |
| • | The TCM stores DTC P0730 in TCM history. |
Conditions for Clearing the MIL/DTC
| • | The PCM turns off the MIL after the third consecutive drive trip in which the TCM does not send a MIL illumination request. |
| • | A scan tool can clear the MIL/DTC. |
| • | The TCM clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring. |
| • | The TCM cancels the DTC default actions when the ignition is OFF long enough to power down the TCM. |
Diagnostic Aids
Ask the customer about overloading the vehicle, or exceeding the trailer towing limit.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step determines that shift solenoid 4 or the U1 shift valve is stuck if the TCC applies in 2nd gear and stalls the engine.
-
This step determines if the output shaft speed sensor signal is skewed by a large factor.
-
This step determines if the input shaft speed sensor signal is skewed by a large factor.
-
This step determines that shift solenoid 2 or the M2 shift valve is stuck if the TCC Slip Speed is near 0 RPM at idle in DRIVE (D).
Step | Action | Values | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Vehicle in Vehicle DTC Information? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | ||||||
2 | Inspect for correct transmission fluid level. Refer to Transmission Fluid Check . Is the transmission fluid level correct? | -- | Go to Step 4 | Go to Step 3 | ||||||
3 |
Did you find and correct the condition? | -- | Go to Step 25 | Go to Step 4 | ||||||
4 |
Important:
Is the 1st gear ratio within the specified range? | 3.68:1-5.52:1 | Go to Intermittent Conditions in Engine Controls - 3.4L | Go to Step 5 | ||||||
Drive the vehicle in 2nd gear. Does the engine stall when the transmission shifts into 2nd gear? | -- | Go to Step 14 | Go to Step 6 | |||||||
Is Transmission OSS parameter reading correctly? | -- | Go to Step 7 | Go to Step 19 | |||||||
Is Transmission ISS parameter within the specified range? | 400-800 RPM | Go to Step 8 | Go to Step 18 | |||||||
Is TCC Slip Speed within the specified range? | 0-100 RPM | Go to Step 13 | Go to Step 9 | |||||||
9 |
Does shift solenoid 1 click when commanded ON? | -- | Go to Step 10 | Go to Step 20 | ||||||
10 | Command shift solenoid 5 ON and OFF with a scan tool. Does shift solenoid 5 click when commanded ON and OFF? | -- | Go to Step 11 | Go to Step 21 | ||||||
11 | Perform a line pressure test. Refer to Line Pressure Check . Is the action complete? | -- | Go to Step 12 | -- | ||||||
12 |
Did you find excessive amounts of sediment? | -- | Go to Step 17 | Go to Step 15 | ||||||
13 | Inspect the control valve body assembly (39) for the following conditions:
Refer to Control Valve Body Assembly Disassemble in Unit Repair. Did you find any of the above conditions? | -- | Go to Step 22 | Go to Step 16 | ||||||
14 | Inspect the control valve body assembly (39) for the following conditions:
Refer to Control Valve Body Assembly Disassemble in Unit Repair. Did you find any of the above conditions? | -- | Go to Step 22 | Go to Step 16 | ||||||
15 | Inspect the control valve body assembly (39) for the following conditions:
Refer to Control Valve Rear Body Disassemble and Control Valve Body Disassemble - Middle in Unit Repair. Did you find any of the above conditions? | -- | Go to Step 22 | Go to Step 16 | ||||||
16 | Has the control valve body been serviced within the past 3 months or 4,828 km (3,000 mi)? | -- | Go to Step 17 | Go to Step 22 | ||||||
17 | Inspect the following items:
Refer to Front Internal Gear and Overrun Roller Clutch Assemble , Forward and Direct Clutch Assembly Assemble , and 1-2-Reverse Clutch Plate Assemble in Unit Repair. Is the action complete? | -- | Go to Step 23 | -- | ||||||
18 | Replace the input shaft speed sensor (73). Refer to Input Speed Sensor Replacement . Is the replacement complete? | -- | Go to Step 25 | -- | ||||||
19 | Replace the output shaft speed sensor (62). Refer to Output Speed Sensor Replacement . Is the replacement complete? | -- | Go to Step 25 | -- | ||||||
20 | Replace the reverse, 1st shift solenoid valve assembly (S1) - black (310). Refer to Control Valve Body Assembly Disassemble in Unit Repair. Is the replacement complete? | -- | Go to Step 25 | -- | ||||||
21 | Replace the reverse shift solenoid valve assembly (S5) - green (305). Refer to Control Valve Body Assembly Disassemble in Unit Repair. Is the replacement complete? | -- | Go to Step 25 | -- | ||||||
22 | Repair or replace the control valve body assembly (39). Refer to Control Valve Body Replacement . Is the action complete? | -- | Go to Step 24 | -- | ||||||
23 | Repair or replace the transmission. Refer to Transmission Replacement . Is the action complete? | -- | Go to Step 24 | -- | ||||||
24 |
Important: The Reset Trans Adapts function will clear all adapt cells. This may affect transmission performance. The TCM will update the adapt cell values as the vehicle is driven.
Did you complete the above procedures? | -- | Go to Step 25 | -- | ||||||
25 | Perform the following procedure in order to verify the repair:
Does the DTC reset? | -- | Go to Step 2 | Go to Step 26 | ||||||
26 | With the scan tool, observe the stored information, capture info and DTC info. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | System OK |
