DTC P0730 Incorrect Gear Ratio 5.7L and 7.4L Gas Only
| Table 1: | 4L80-E Range Reference, modified for DTCs P1870 & P1871 |
| Table 2: | P0730 (97 C/K & G600 VCM) |
Range | Gear | 1-2 Sol | 2-3 Sol | Fourth Clutch | Overrun Clutch | O/D Roller Clutch | FWD Clutch | Direct Clutch | Front Band | Interm. Sprag Clutch | Interm Clutch | Lo Roller Clutch | Rear Band |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Overdrive | 1st | On | Off | -- | -- | H | A | -- | -- | * | -- | H | -- |
2nd | Off | Off | -- | -- | H | A | -- | -- | H | A | O | -- | |
3rd | Off | On | -- | -- | H | A | A | -- | O | A | O | -- | |
4th | On | On | A | -- | O | A | A | -- | O | A | O | -- | |
| |||||||||||||
Circuit Description
The Vehicle Control Module (VCM) calculates the gear ratio based on the Automatic Transmission Input Shaft Speed (A/T ISS) and Output Shaft Speed (OSS) Sensor readings. The VCM compares the known transmission ratio calibration values to the calculated ratio.
If the VCM detects an unknown ratio, then DTC P0730 sets. DTC P0730 is a type D DTC.
Conditions for Setting the DTC
The following conditions are met for 10 seconds.
| • | No TP DTCs P0121, P0122 or P123. |
| • | No OSS DTC P0502. |
| • | No A/T ISS DTCs P0716 or P0717. |
| • | No TFP Val. Position Sw. DTC P1810. |
| • | No Four Wheel Drive Lo DTC 1875. |
| • | The Four Wheel Drive Lo fail counters are clear. |
| • | The Vehicle Speed is greater than 11 km/h (7 mph) |
| • | The TP Angle is greater than 25%. |
| • | The TFT is greater than 20°C (68°F) |
| • | 10 seconds must have elapsed since the last gear range change. |
| • | The engine torque is 100 N·m (80 lb ft) to the following: |
| - | 470 N·m (375 lb ft) 5.7L |
| - | 627 N·m (500 lb ft) 7.4L |
| • | The engine is running for greater than 5 seconds and is not in fuel cut off. |
| • | The engine vacuum is 0-105 kPa. |
| • | The Gear Ratio is one of the following: |
| - | Greater than 2.63 or less than 2.38 |
| - | Greater than 1.58 or less than 1.43 |
| - | Greater than 1.05 or less than 0.95 |
| - | Greater than 0.80 or less than 0.70 |
| - | Greater than 2.17 or less than 1.97 |
Action Taken When the DTC Sets
| • | The VCM commands maximum line pressure. |
| • | The VCM freezes shift adapts. |
Conditions for Clearing the DTC
- A scan tool can clear the DTC from the VCM history. The VCM clears the DTC from the VCM history if the vehicle completes 40 warm-up cycles without a failure reported.
- The VCM cancels the DTC default actions when the fault no longer exists and the ignition is OFF long enough in order to power down the VCM.
Diagnostic Aids
| • | Inspect the wiring for poor electrical connections at the VCM. Inspect the wiring for poor electrical connections at the transmission 20-way connector. Look for the following problems: |
| - | A bent terminal |
| - | A backed out terminal |
| - | A damaged terminal |
| - | Poor terminal tension |
| - | A chafed wire |
| - | A broken wire inside the insulation |
| • | When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change. |
| • | First diagnose and clear any engine DTCs or TP Sensor codes that are present. Then inspect for any transmission DTCs that may have reset. |
| • | A false or incorrect A/T OSS or A/T ISS signal can set DTC P0730. |
| • | Sticking or contaminated shift valves may cause intermittent incorrect gear ratios. |
| • | Inspect for any improperly installed after-market equipment. |
| • | 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.
-
This Step tests the indicated range signal to the actual selected range. A faulty TFP Val. Position Sw. could set DTC P1810.
-
This step tests for proper ratios in each commanded gear state.
Step | Action | Value(s) | Yes | No | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||||||||||||||
2 | Perform the transmission fluid checking procedure. Refer to Transmission Fluid Check . Is the procedure complete? | -- | Go to Transmission Fluid Check | |||||||||||||
Important: Before clearing the DTCs, use the scan tool in order to record the Freeze Frame and Failure Records for reference. The Clear Info function will erase the data. Does the scan tool TFP Switch A/B/C display match each selected gear range? (Refer to the Range Signal ) table. | -- | Refer to DTC P1810 Pressure Switch Assembly Malfunction , in this section | ||||||||||||||
Are the gear ratios within the parameters for each specified range? (Refer to the Gear Ratio table.) | -- | Refer to Diagnostic Aids | ||||||||||||||
5 |
Refer to the Line Pressure Check . Is the line pressure within specifications for each selected gear range? | -- | ||||||||||||||
6 |
Refer to Changing the Fluid and Filter, in On-Vehicle Service. Did you find excessive contamination? | -- | Go to Transmission Overhaul , in Unit Repair | |||||||||||||
7 | Inspect the transmission for the following problems:
Did you find a problem? | -- | Go to Transmission Overhaul , in Unit Repair | |||||||||||||
8 | Is the system line pressure low only in the specific gear which indicated an incorrect gear ratio? | -- | Go to the System Diagnosis table; Low Line Pressure | |||||||||||||
9 | Inspect for fluid pressure loss in the following areas:
Did you find a problem? | -- | Go to Transmission Overhaul , in Unit Repair | |||||||||||||
10 | In order to verify your repair, perform the following procedure:
Has the test run and passed? | -- | System OK |
