DTC P0730 Incorrect Gear Ratio. Cadillac DeVille 1996

For 1990-2009 cars only

Makes 🢒 Cadillac 🢒 1996 🢒 DeVille 🢒 DTC 🢒 DTC P0730 Incorrect Gear Ratio

Table 1:	4T80-E Range Reference, modified for use as P0730 Thumbnail
Table 2:	Gear Ratios
Table 3:	DTC P0730 Incorrect Gear Ratio

4T80-E Range Reference, modified for use as P0730 Thumbnail

Range	Reverse	D4				D3			D2		D1
Gear	R	1st	2nd	3rd	4th	1st	2nd	3rd	1st	2nd	1st	2nd
1-2 Shift Solenoid	ON	ON	OFF	OFF	ON	ON	OFF	OFF	ON	OFF	ON	OFF
2-3 Shift Solenoid	OFF	OFF	OFF	ON	ON	OFF	OFF	ON	OFF	OFF	OFF	OFF
Forward	--	A	A	A	A	A	A	A	A	A	A	A
Coast	--	--	--	--	--	--	--	A	A	A	A	A
3rd Clutch	--	--	--	A	A	--	--	A	--	--	--	--
2nd Clutch	--	--	A	A	A	--	A	A	--	A	--	A
Reverse	A	--	--	--	--	--	--	--	--	--	--	--
4th Band	--	--	--	--	A	--	--	--	--	A	--	A
Lo/Rev Band	A	A	--	--	--	A	--	--	A	--	A	--
Lo Roller	--	H	--	--	--	H	--	--	H	--	H	--
2nd Sprag	--	--	H	--	--	--	H	--	--	H	--	H
Forward Sprag	--	H	H	H	--	H	H	H	H	H	H	H
A = Applied H = Holding ON = The solenoid is energized. OFF = The solenoid is de-energized

Circuit Description

The Powertrain Control Module (PCM) calculates gear ratio based on data from the Automatic Transmission Input (Shaft) and Output(Shaft) Speed sensors. The PCM compares the known transmission gear ratio to a calculated ratio for each gear range selected.

DTC P0730 sets if the steady state adapts are at their maximum, and the PCM detects an incorrect gear ratio because of excessive slip within the transmission. DTC P0730 is a Type C DTC.

Conditions for Setting the DTC

•	No MAF DTCs P0101, P0102 or P0103 are set.

•	No TP DTCs P0121, P0122 or P0123 are set.

•	No VSS DTCs P0502 or P0503 are set.

•	No A/T ISS DTCs P0716 or P0717 are set.

•	No 1-2 shift solenoid valve electrical DTC P0753 is set.

•	No 2-3 shift solenoid valve electrical DTC P0758 is set.

•	No TFP Val Position Sw. DTC P1810 is set.

•	Engine running for more than 5 seconds.

•	The vehicle speed is greater than 11 km/h (7 mph).

•	The throttle angle is greater than 15.7°.

•	The automatic transmission range switch is not indicating park or neutral.

•	At least one steady state adapt cell is at maximum.

•	The transmission fluid temperature is greater than 20°C (68°F).

•	Delivered torque is greater than 135 N·m (100 lb ft)

•	All of the following fail cases are true for 4 seconds:

-	First gear ratio is less than 2.87 or greater than 3.11.

-	Second gear ratio is less than 1.54 or greater than 1.71.

-	Third gear ratio is less than 0.95 or greater than 1.05.

-	Fourth gear ratio is less than 0.65 or greater than 0.71.

-	Reverse gear ratio is less than 2.02 or greater than 2.23.

Action Taken When the DTC Sets

•	SERVICE TRANSMISSION displays on the Driver Information Center (DIC).

•	The PCM commands maximum line pressure.

•	The PCM disable steady state adapts.

•	The PCM disable upshift adapts.

•	The PCM disable garage shift adapts.

•	The PCM inhibits torque management.

Conditions for Clearing the DIC/DTC

•	The PCM sees a correct gear ratio in each gear range for 4 seconds.

•	A scan tool can clear the DTC from the PCM history. The PCM clears the DTC from the PCM history if the vehicle completes 40 warm-up cycles without a failure reported.

Diagnostic Aids

Ensure that the vehicle's final drive ratio matches PROM calibration.

Refer to Range Reference

Gear Ratios

Gear	Ratio
First	2.96
Second	1.63
Third	1.00
Fourth	0.68
Reverse	2.13

Test Description

The numbers below refer to the steps on the diagnostic chart.

This Step ensures that you performed the Powertrain On-Board Diagnostic System Check.

This Step verifies that you inspected the transmission fluid and that the fluid is at the proper level. An under-filled transmission could result in insufficient hydraulic line pressure causing the transmission to slip.

This Step inspects for additional DTCs. If a VSS or A/T ISS DTC is set, refer to those DTC charts first.

This Step installs the J 21867 Pressure Gauge along with the J 21867-94 Line Pressure Fitting. With the engine running (in Park), control the amount of current through the Pressure Control Solenoid Valve (PC Sol. Valve) while monitoring the pressure gauge.

This Step replaces the Pressure Control Solenoid Valve which caused the high line pressure.

This Step inspects and either replaces or repairs the faulty components that caused the low line pressure.

Set the scan tool in snapshot mode. Monitor the following three parameters:

Important: When driving the vehicle in Reverse, the commanded gear will be first.

•	Automatic Transmission Fluid Pressure Manual Valve Position switch (TFP Val. Position Sw.)

•	Transmission gear ratio

•	Commanded gear

This Step inspects the reverse clutch and LO reverse band for slippage when the vehicle is placed in Reverse and the ratio is too high (2.22).

This Step inspects the valve body for hydraulic failure when the vehicle was placed in Reverse (2.02).

This Step instructs the technician to drive the vehicle with the gear select lever in the Overdrive range. Compare the snapshot data with the value column.

This Step inspects and repairs the faulty components that caused a ratio greater than 1.05.

This Step inspects and repairs the faulty components that caused a ratio greater than 1.71.

This Step inspects and repairs the faulty components that caused a ratio greater than 1.54.

This Step inspects and repairs the faulty components that caused a ratio greater than 2.87.

This Step instructs the technician to drive the vehicle with the gear select lever in the D3 range. Compare the snapshot data with the value column.

This Step inspects and repairs the faulty components that caused a ratio less than 0.95.

This Step inspects and repairs the faulty components that caused a ratio that was less than 0.95 but greater than 0.71.

This Step inspects and repairs the faulty components that caused a ratio greater than 1.05.

This Step inspects and repairs the faulty components that caused a ratio greater than 1.71.

This Step inspects and repairs the faulty components that caused a ratio less than 1.54.

This Step inspects and repairs the faulty components that caused a ratio less than 2.87.

This Step instructs the technician to drive the vehicle with the gear select lever in the D2 range. Compare the snapshot data with the value column.

This Step inspects and repairs the faulty components that caused a ratio less than 1.54.

This Step inspects and repairs the faulty components that caused a ratio greater than 1.05.

This Step inspects and repairs the faulty components that caused a ratio greater than 1.71.

This Step inspects and repairs the faulty components that caused a ratio less than 1.54.

This Step inspects and repairs the faulty components that caused a ratio less than 2.87.

This Step instructs the technician to drive the vehicle with the gear select lever in the D1 (low) range. Compare the snapshot data with the value column.

This Step inspects and repairs the faulty components that caused a ratio less than 2.87.

This Step inspects and repairs the faulty components that caused a ratio greater than 3.11.

This Step replaces the PCM after you inspect the components.

DTC P0730 Incorrect Gear Ratio

Step

Action

Value(s)

Yes

Was the Powertrain On-Board Diagnostic (OBD) System Check performed?

Go to Step 2

Go to A Powertrain On Board Diagnostic (OBD) System Check

Has the transmission fluid checking procedure been performed?

Go to Step 3

Go to Transmission Fluid Check

Install the scan tool (tech 1) .
With the engine OFF, turn the ignition switch to the RUN position.

Important: Before clearing the DTCs, use the scan tool in order to record the Failure Records for reference. The Clear Info function will erase the data.

Record the DTC Failure Records.

Are any of the following DTCs set: P0502, P0503, P0716, P0717, P0753, or P0758?

Go to Step 4

Go to Step 5

Diagnose these DTCs.
Repair these DTCs first.

Did you diagnose and correct the condition?