P0734 (54) - Speed Ratio Error in 4th
Name of Code:P0734 (54) - Speed Ratio Error in 4th
When Monitored:
The transmission gear ratio is monitored continuously while the transmission is in gear.
Set Condition:
This code is set if the gear ratio is not correct for the current gear.
- Codes 50 through 55 sets if the ratio of the input RPM (Nt) to the output RPM (No) does not match the current gear ratio.
- Code 56 sets if there is an excessive change in input RPM in any gear
- Code 57 sets if there is an excessive change in output RPM in any gear
- Code 58 sets after a TCM reset in neutral and Nt/No equals a ratio of input to output of 2.00
Theory of Operation:
The transmission system uses two speed sensors, one to measure input RPM and one to measure output RPM. These inputs are essential for proper transmission operation. Therefore, the integrity of this data is verified through the following checks:
1) When in gear, if the gear ratio does not compare to a known gear ratio, the corresponding in-gear trouble code is set (codes 50 through 55).
2) An excessive change in input or output speeds indicating signal intermittency will result in codes 56 and/or 57 being set.
3) If the common speed sensor ground circuit is lost, both sensor inputs will read the output from the input speed sensor at idle in neutral. Since the input speed sensor has 60 teeth and the output speed sensor has 30 teeth, this results in a ratio of 2.00.
Transmission Effects:
If a gear ratio error develops, the appropriate code is set as a one trip failure and the 5 minute Intelligent Recovery Timer (IRT) is started. The transmission will then substitute a different gear for the one in which the problem was identified. For example, if a problem is identified while in second gear, the transmission will shift to third gear. The IRT is only counting up while the transmission is substituting one gear for another. Using the previous example, if the vehicle continued down the road and shifted to fourth gear for a long period of time, the IRT would have only counted the time that the transmission was in third gear instead of second. The MIL will illuminate and the transmission system will default to the Logical Shutdown with Full Recovery (R) routine after 5 minutes of substituted gear operation or if three gear ratio error events occur in a given key start.
Possible Causes:
Code P0736 (50) - Excludes geartrain failures which should be obvious upon disassembly
- If code P1791 (35) or any line pressure DTC's are set, diagnose these first
- Valve body - #3 ball check
- L-R switch valve sticking - may also set code P0731 (51)
- Speed sensor or associated wiring - may also set codes P0731 (51), P0715 (56), or P0720 (57)
- Multi Select Solenoid sticking or leaking
- Failed or slipping L-R clutch - may also set code P0731 (51)
- L-R seal leakage (Intermittent no drive or reverse)
- Sticky L-R accumulator seals (Intermittent no drive or reverse)
- Failed reverse clutch (hard code)
- OD/Rev lip seal leakage
- Worn reaction shaft support seal rings
Code P0731 (51) - Excludes geartrain failures which should be obvious upon disassembly
- If code P1791 (35) or any line pressure DTC's are set, diagnose these first
- Valve body - #1, #2, and/or #4 ball check
- L-R switch valve sticking
- Speed sensor or associated wiring wiring - may also set codes P0736 (50), P0715 (56), or P0720 (57)
- Solenoid/TRS assembly (stuck solenoid (s))
- Failed or intermittent slipping UD clutch - may also set P0732 (52) or P0733 (53)
- UD seal leakage
- Sticky UD accumulator seals
- Worn reaction shaft support seal rings
- Failed or slipping L-R clutch - may have code P0736 (50)
- L-R seal leakage
- Sticky L-R accumulator seals Code P0732 (52) - Excludes geartrain failures which should be obvious upon disassembly
- If code P1791 (35) or any line pressure DTC's are set, diagnose these first
- Valve body - #1, #2, #4, #5 and/or #7 ball check
- Solenoid/TRS assembly - may also set codes P1734 (54) and/or P1728 (A2)
- Failed or slipping 2nd clutch
- 2nd clutch seal leakage
- Sticky 2nd clutch accumulator seals
- Failed or intermittent slipping UD clutch - may also set code P0731 (51) and/or P0732 (52)
- UD clutch seal leakage
- Worn input hub bushing
- Sticky UD clutch accumulator seals
- Worn reaction shaft support seal rings
Code P0734 (54) - Excludes geartrain failures which should be obvious upon disassembly
- If code P1791 (35) or any line pressure DTC's are set, diagnose these first
- Valve body - #1, #2, and/or #6 ball check
- Speed sensor or associated wiring - may also set codes P0736 (50), P0715 (56), or P0720 (57)
- Solenoid/TRS assembly - may also set codes P1781 (84) and/or P1787 (A4)
- Failed or slipping OD clutch - may also set code P0734 (54)
- OD clutch inner and outer lip seal leakage
- Sticky OD clutch accumulator seals
- Worn reaction shaft support seal rings
- Failed or intermittent slipping UD clutch - may also set codes P0731 (51) and/or P0732 (52)
- UD seal leakage
- Worn input hub bushing
- Sticky UD clutch accumulator seals
- Worn reaction shaft support seal rings Code P0734 (54)
- Excludes geartrain failures which should be obvious upon disassembly
- If code P1791 (35) or any line pressure DTC's are set, diagnose these first
- Valve body - #1, #2, #5 and/or #6 ball check
- Speed sensor or associated wiring - may also set codes P0736 (50), P0715 (56), or P0720 (57)
- Solenoid/TRS assembly - may also set codes P1733 (88) and/or P1727 (A8)
- Failed or slipping OD clutch - may also set code P0733 (53)
- OD clutch inner and outer lip seal leakage
- Sticky OD clutch accumulator seals
- Worn reaction shaft support seal rings
- Failed or intermittent slipping 4th clutch
- 4TH clutch seal leakage
- Sticky 4th clutch accumulator seals
- Worn reaction shaft support seal rings
Code P1736 (55) - Excludes geartrain failures which should be obvious upon disassembly
- If code P1791 (35) or any line pressure DTC's are set, diagnose these first
- Valve body - #1, #4 and/or #5 ball check
- Speed sensor or associated wiring - may also set codes P0736 (50), P0715 (56), or P0720 (57)
- Solenoid/TRS assembly - may also set codes P1732 (90) and/or P1726 (BO)
- Failed or intermittent slipping UD clutch - may also set codes P0731 (51) and/or P0732 (52)
- UD seal leakage
- Worn input hub bushing
- Sticky UD clutch accumulator seals
- Worn reaction shaft support seal rings
- Failed or intermittent slipping 4th clutch
- 4th clutch seal leakage
- Sticky 4th clutch accumulator seals
- Worn reaction shaft support seal rings Codes P0715 (56) and P0720 (57)
- Failed input or output speed sensor
- Shorted or open wiring between TCM and speed sensor (s)
- Connector problems at 60-way TCM connector and/or speed sensor connector (s) Code P1794 (58)
- Open or shorted speed sensor ground (speed sensor ground is different from chassis ground)
- Open or shorted Temperature Sensor wiring to TRS
- TRS - Will also set code P1799 (74)
- TCM