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Old 07-14-2010, 09:30 PM
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P0731 Gear 1 Ratio Incorrect

I have a 1999 Grand Cherokee Larado and it has a P0731 Gear 1Ratio Incorrect error. I can not find any details on what causes this error or how to fix it. I've been told that it could be the vehicle speed sensor. I've already changed the output speed sensor before this problem occured for a different error so maybe it is the input speed sensor. any help would be great.

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Old 08-14-2010, 02:59 PM
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Re: P0731 Gear 1 Ratio Incorrect

Did you solve your problem in the mean time? If not, the following could help:

DTC P0731 [FN4A-EL]



B3E050219090W14



DTC P0731


Gear 1 incorrect (incorrect gear ratio detected)

DETECTION CONDITION
The PCM monitors the revolution ratio of the forward clutch drum revolution to differential gear case revolution when the following monitoring conditions are met. If the revolution ratio is below 2.16, the PCM determines that there is a malfunction.
Monitoring condition: - ATF temperature 20 C {68 F} or more - Driving in 1GR in D or M range - Engine running - Turbine speed within 225-4,987 rpm - Throttle opening angle 2.66% or more - Differential gear case (output) revolution speed 35 rpm or more. - None of the following present: DTC P0500, P0706, P0707, P0708, P0712, P0713, P0715, P0751, P0752, P0753, P0756, P0757, P0758, P0761, P0762, P0763, P0766, P0767, P0768, P0771, P0772, P0773 Diagnostic support note: This is a continuous monitor (CCM).
The MIL does not illuminate.
The AT warning light illuminates if the PCM detects the above malfunction condition during the first drive cycle.
FREEZE FRAME DATA is not available.
A PENDING CODE is not available.
The DTC is stored in the PCM memory.
POSSIBLE CAUSE
ATF level low
Deteriorated ATF
Shift solenoid A stuck
Pressure control solenoid stuck
Line pressure low
One-way clutch slipping
Forward clutch slipping
Control valve stuck
Oil pump malfunction
PCM malfunction

Diagnostic procedure

STEP


INSPECTION


ACTION

1
VERIFY RELATED REPAIR INFORMATION AVAILABILITY
Verify related Service Bulletins and/or on-line repair information availability.
Is any related repair information available?
Yes
Perform repair or diagnosis according to the available repair information.
No
Go to the next step.
2
INSPECT ATF CONDITION
Inspect the ATF condition.
(See AUTOMATIC TRANSAXLE FLUID (ATF) INSPECTION.)
Is it normal?
Yes
Go to the next step.
No
Replace the transaxle, then go to Step 8.
3
INSPECT ATF LEVEL
Start the engine.
Warm up the ATX.
Is the ATF level within the specification?
(See AUTOMATIC TRANSAXLE FLUID (ATF) INSPECTION.)
Yes
Go to the next step.
No
Add ATF to the specified level, then go to Step 8.
4
INSPECT SHIFT SOLENOID VALVE A
Perform operation inspection.
(See SOLENOID VALVE INSPECTION.)
Verify the click sound of shift solenoid A when applying B+ to transaxle terminal A.
Was a click heard from solenoids?
Yes
Go to the next step.
No
Replace the solenoid that you could not hear a click sound, then go to Step 8.
(See SOLENOID VALVE REMOVAL/INSTALLATION.)
5
INSPECT LINE PRESSURE
Start the engine.
Measure the line pressures.
Specification
Idle: 330-470 kPa {3.4-4.7 kgf/cm2, 48-68 psi}
Stall:
1,090-1,250 kPa {11.2-12.7 kgf/cm2, 159-181 psi} (Z6)
1,160-1,320 kPa {11.8-13.5 kgf/cm2, 168-191 psi} (LF)
Are the line pressures within the specifications?
(See Line Pressure Test.)
Yes
Go to the next step.
No
All ranges: Replace the oil pump, then go to Step 8.
Any ranges: Replace the control valve body, then go to Step 8. (See CONTROL VALVE BODY REMOVAL.)
(See CONTROL VALVE BODY INSTALLATION.)
6
INSPECT STALL SPEED
Measure the stall speed in D range.
(See Stall Test.)
Specification
2,100-2,700 rpm (Z6)
2,000-2,600 rpm (LF)
Is the stall speed within the specification?
Yes
Go to the next step.
No
Replace the automatic transaxle, then go to Step 8.
(See AUTOMATIC TRANSAXLE REMOVAL/INSTALLATION [Z6].)
(See AUTOMATIC TRANSAXLE REMOVAL/INSTALLATION [LF].)
7
INSPECT FREQUENCY OF INPUT/TURBINE SPEED SENSOR WHEN DRIVING VEHICLE
Turn the ignition switch to the LOCK position.
Connect the WDS or equivalent.
Start the engine.
Measure the frequency of input/turbine speed sensor while driving vehicle under the following conditions:
- Vehicle speed (VSS PID): 20 km/h {12 mph} - Drive in the D range, 1GR - Throttle opening angle (TP PID): approx. 25% Was the frequency of the input/turbine speed sensor at approx. 1,100 Hz?
Yes
Go to the next step.
No
Replace the control valve body, then go to the next step.
(See CONTROL VALVE BODY REMOVAL.)
(See CONTROL VALVE BODY INSTALLATION.)
8
VERIFY REPAIR OF DTC P0731
Make sure to reconnect all the disconnected connectors.
Clear the DTC using the WDS or equivalent.
Start the engine.
Warm up the transaxle.
Drive the vehicle under the following conditions at least 4 times for more than 1 s:
- ATF temperature: 20 C {68 F} or more - Drive in the D range, 1GR - Throttle opening angle (TP PID): 5.67% or more - Vehicle speed (VSS PID): 4 km/h {3 mph} or more Are any DTCs present?
Yes
Replace the PCM, then go to the next step.
(See PCM REMOVAL/INSTALLATION [ZJ, Z6].)
(See PCM REMOVAL/INSTALLATION [LF].)
No
Go to the next step.
9
VERIFY AFTER REPAIR PROCEDURE
Perform the "After Repair Procedure".
(See AFTER REPAIR PROCEDURE [FN4A-EL].)
Are any DTCs present?
Yes
Go to the applicable DTC inspection.
No
DTC troubleshooting completed.
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