Limp mode repair?

Good afternoon.

Below are the description and possibilities.

You need to take it to someone who will do the proper diagnostics to determine the failure. Clearing the codes does nothing as the issue needs to be addressed.

It could be electrical or mechanical as the charts show.

Roy

734

P0734
Descriptor
Gear Ratio Error In 4Th
Probable Causes
Code Is Not Matching in Service Info File
Intermittent Gear Ratio Errors
Related Transmission DTCs Present
Transmission Mechanical Condition
Transmission Solenoid/Pressure Switch Assembly

Flow chart

Theory of Operation

The transmission control system uses three speed sensors, one to measure input rpm, one to measure Transfer Speed output rpm of the main transmission assembly, and a third to measure the final transmission output rpm. These inputs are essential for proper transmission operation. Therefore, the integrity of this data is verified through system checks. When in gear, if the gear ratio does not compare to a known gear ratio, the corresponding gear ratio error trouble code is set. The transmission will go into Limp-in mode after four gear ratio error events occur in a given driving cycle.

- When Monitored:
The Transmission gear ratio is monitored continuously while the transmission is in gear.

- Set Condition:
If the ratio of the Input RPM to the Output RPM does not match the current gear ratio when compared to the known gear ratio.

Image

Always perform the 62TE Pre-Diagnostic Troubleshooting procedure before proceeding. See: Computers and Control Systems > Initial Inspection and Diagnostic Overview > Pre-Diagnostic Troubleshooting Procedure

1. CHECK IF RELATED TRANSMISSION DTCS ARE PRESENT
1. With the scan tool, read Transmission DTCs.
2. If any of these DTCs are present, perform their respective tests first.

Are there any Loss of Prime, Line Pressure Sensor and/or Speed Sensor DTCs present?

Yes

- Refer to appropriate diagnostic procedure in the Transmission category. If any of these DTCs are present, they will cause a gear ratio error. Perform the test for Loss of Prime first if it is present.
- Perform 62TE TRANSMISSION VERIFICATION TEST See: A L L Diagnostic Trouble Codes ( DTC ) > Verification Tests > 62TE Transmission Verification Test

No

- Go To 2

2. CHECK IF THE DTC IS CURRENT
1. With the scan tool, record the DTC Event Data, clear the DTC and road test the vehicle.
2. Try to duplicate the conditions in which the DTC originally set using the DTC EVENT DATA recorded.

Did the DTC P0734 reset?

Yes

- Repair internal Transmission as necessary. Check all of the components related to the UD, OD, DC and LC clutches. Inspect the Oil Pump and repair or replace as necessary. Refer to the Service Information for the proper repair procedures.
- Perform 62TE TRANSMISSION VERIFICATION TEST See: A L L Diagnostic Trouble Codes ( DTC ) > Verification Tests > 62TE Transmission Verification Test

No

- Go To 3

3. CHECK FOR INTERMITTENT OPERATION
1. The conditions to set this DTC are not current at this time.
2. Check the gearshift linkage adjustment.
3. Gear ratio DTC's can be set by problems in the Input and Output Speed Sensor circuits. If the vehicle passes the Clutch Test and still sets a Gear Ratio DTC, check the Speed Sensors for proper operation.
4. Remove the Starter Relay.

CAUTION: Removal of the Starter Relay will prevent the vehicle from being started in gear.

WARNING: The Starter Relay must be removed. Failure to do so can result in possible serious or fatal injury.

5. Check the wiring and connectors for the Speed Sensors for a good connection, then perform a wiggle test using the Transmission Simulator, Miller tool #8333A and the Electronic Transmission Adapter kit.
6. This DTC can also be set under extreme temperature conditions, this is usually caused by an internal problem. Verify if the problem is only experienced under extreme hot or cold conditions.
7. With the scan tool, check the EATX DTC EVENT DATA to help identify the conditions in which the DTC was set.
8. Check for Service Information Tune-ups or Service Bulletins for any possible causes that may apply.

Were there any problems found?

Yes

- Repair as necessary.
- Perform 62TE TRANSMISSION VERIFICATION TEST See: A L L Diagnostic Trouble Codes ( DTC ) > Verification Tests > 62TE Transmission Verification Test

No

- Test Complete.

792

P0792
Descriptor
Compounder Speed Ratio Error
Probable Causes
Intermittent Gear Ratio Errors
Related Transmission DTCs Present
Transmission Mechanical Condition

flow chart

P0792-COMPOUNDER SPEED RATIO ERROR

Theory of Operation

The transmission control system uses three speed sensors, one to measure input rpm, one to measure Transfer Speed output rpm of the main transmission assembly, and a third to measure the final transmission output rpm. These inputs are essential for proper transmission operation. Therefore, the integrity of this data is verified through system checks.

- When Monitored:
The transmission gear ratio is monitored continuously while the transmission is in gear.

- Set Condition:
If there is an excessive change in the Output RPM in any gear.

Image

Always perform the 62TE Pre-Diagnostic Troubleshooting procedure before proceeding. See: Computers and Control Systems > Initial Inspection and Diagnostic Overview > Pre-Diagnostic Troubleshooting Procedure

1. DETERMINING IF RELATED TRANSMISSION DTCS ARE PRESENT
1. With the scan tool, read Transmission DTCs.
2. If any of these DTCs are present, perform their respective tests first.

Are there any Loss of Prime, Line Pressure Sensor and/or Speed Sensor DTCs present?

Yes

- Refer to appropriate diagnostic procedure in the Transmission category. If any of these DTCs are present, they will cause a gear ratio error. Perform the test for Loss of Prime first if it is present.
- Perform 62TE TRANSMISSION VERIFICATION TEST See: A L L Diagnostic Trouble Codes ( DTC ) > Verification Tests > 62TE Transmission Verification Test

No

- Go To 2

2. CHECK TO SEE IF P0792 IS CURRENT
1. With the scan tool, record the DTC Event Data, clear the DTC and road test the vehicle.
2. Try to duplicate the conditions in which the DTC originally set using the DTC EVENT DATA recorded.

Did the DTC P0792 reset?

Yes

- Repair internal Transmission as necessary. Check all of the components related to the DC and LC clutches. Inspect the Oil Pump and repair or replace as necessary. Refer to the Service Information for the proper repair procedures.
- Perform 62TE TRANSMISSION VERIFICATION TEST See: A L L Diagnostic Trouble Codes ( DTC ) > Verification Tests > 62TE Transmission Verification Test

No

- Go To 3

3. CHECK FOR INTERMITTENT OPERATION
1. The conditions to set this DTC are not current at this time.
2. Check the gearshift linkage adjustment.
3. Gear ratio DTCs can be set by problems in the Input and Output Speed Sensor circuits. If the vehicle passes the Clutch Test and still sets Gear Ratio DTC, check the Speed Sensors for proper operation.
4. Remove the Starter Relay.

CAUTION: Removal of the Starter Relay will prevent the vehicle from being started in gear.

WARNING: The Starter Relay must be removed. Failure to do so can result in possible serious or fatal injury.

5. Check the wiring and connectors for the Speed Sensors for a good connection, then perform a wiggle test using the Transmission Simulator, Miller tool #8333A and the Electronic Transmission Adapter kit.
6. This DTC can also be set under extreme temperature conditions. This is usually caused by an internal problem. Verify if the problem is only experienced under extreme hot or cold conditions.
7. With the scan tool, check the DTC EVENT DATA to help identify the conditions in which the DTC was set.
8. Check for Service Information Tune-ups or Service Bulletins for any possible causes that may apply.

Were there any problems found?

Yes

- Repair as necessary.
- Perform 62TE TRANSMISSION VERIFICATION TEST See: A L L Diagnostic Trouble Codes ( DTC ) > Verification Tests > 62TE Transmission Verification Test

No

- Test Complete.

The diagnostic is about a two hour job to do it properly. That would be around $200.00 to $250.00.

If it is mechanical, then yes, it is a rebuild. That would be around $2,000.00 to $2,500.00.

Roy

By "does not shift", do you mean it stays in second gear?

You already found the first clue in that you do not have to be moving for it to go to limp mode. That eliminates slippage in one of the clutch packs. Since you have a scanner, use it to read and record the diagnostic fault codes in the Transmission Computer. Those will tell us which circuit needs further diagnosis.

Not to my knowledge. If you have a simple fault code reader, you can use that to see if anything useful comes up. The problem is you need to read the codes in the Transmission Computer, and most code readers only read them in the Engine Computer. Typically when there is a code in the Transmission Computer that puts it in limp mode, that results in seriously-decreased fuel mileage, and therefore, increased emissions, and any fault code related to something that could adversely affect emissions will turn on the Check Engine light. The fault code found in the Engine Computer then is code 700 which just means there is some other code in the Transmission Computer. Without knowing the exact code number, there is no practical way to know where to start the diagnosis. All we know is it is going to be electrical in nature.

Some of us would be tempted to just start replacing random parts, but you are much better off waiting for the scanner. Every new part introduces a new variable and potential second problem. Simply unplugging a connector and reconnecting it can temporarily solve a problem, and that is exactly what we do not want to have happen. We want to know which circuit has the problem, and we want to know exactly what we did to make the problem go away, so we know what the proper fix is.

Please let us know what you find. We are interested to see what it is.

Cheers, Ken

Yep, that is what that means. The computer is having issues. Here is the location so you can replace it I would try a used one. The TCJM is subject to water damage so it makes sense.

Check out the diagrams (below). Please let us know what happens.

Cheers, Ken

It could be the the wiring but it sounded like you checked that in your first post. I will be happy to back over it will you with this guide and the TCM wiring diagrams below.

Please check power and grounds and test through the transmission range sensor.

https://www.2carpros.com/articles/how-to-check-wiring

Please run down these guides and diagrams and report back.

Cheers, Ken

Hello,

Okay the first thing we need to do is code for codes here is a guide to help you see whats going on. It sounds like a transmission shaft speed sensor.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Please run down this guide and report back

Cheers, Ken

Nice work, we are here to help, please use 2CarPros anytime.

Cheers, Ken