Part 2 of 2

Name of code:
P-0736(50) - Speed Ratio Error in Reverse
P-0731(51) - Speed Ratio Error in 1st
P-0732(52)- Speed Ratio Error in 2nd
P-0733(53) - Speed Ratio Error in 3rd
P-0734(54) - Speed Ratio Error in 4th
P-1736(55) - Speed Ratio Error in 2nd Prime
P-0715 (56) - Input Speed Sensor
P-0720(57) - Output Speed Sensor
P-1794(58) - Speed Sensor Ground

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 P-0736(50) - Excludes geartrain failures which should be obvious upon disassembly
^ If code P-1791(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 P-0731(51)
^ Speed sensor or associated wiring - may also set codes P-0731(51), P-0715(56), or P-0720(57)
^ Multi Select Solenoid sticking or leaking
^ Failed or slipping L-R clutch - may also set code P-0731(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 P-0731(51) - Excludes geartrain failures which should be obvious upon disassembly
^ If code P-1791(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 P-0736(50), P-0715(56), or P-0720(57)
^ Solenoid/TRS assembly (stuck solenoid(s))
^ Failed or intermittent slipping UD clutch may also set P-0732(52) or P-0733(53)
- UD seal leakage
- Sticky UD accumulator seals
- Worn reaction shaft support seal rings
^ Failed or slipping L-R clutch - may have code P-0736(50)
- L-R seal leakage
- Sticky L-R accumulator seals
^ Code P-0732(52) - Excludes geartrain failures which should be obvious upon disassembly
^ If code P-1791(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 P-1734(54) and/or P-1728(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 P-0731(51) and/or P-0733(53)
- UD clutch seal leakage
- Worn input hub bushing
- Sticky UD clutch accumulator seals
- Worn reaction shaft support seal rings
^ Code P-0733(53) - Excludes geartrain failures which should be obvious upon disassembly
^ If code P-1791(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 P-0736(50), P-0715(56), or P-0720(57)
^ Solenoid/TRS assembly - may also set codes P-1781(84) and/or P-1787M)
^ Failed or slipping OD clutch - may also set code P-0734(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 P-0731(51) and/or P-0732(52)
- UD seal leakage
- Worn input hub bushing
- Sticky UD clutch accumulator seals -Worn reaction shaft support seal rings
^ Code P-0734(54) - Excludes geartrain failures which should be obvious upon disassembly
^ If code P-1791(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 P-0736(50), P-0715(56), or P-0720(57)
^ Solenoid/TRS assembly - may also set codes P-1733(88) and/or P-1727(A8)
^ Failed or slipping OD clutch - may also set code P-0733(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 P-1736(55) - Excludes geartrain failures which should be obvious upon disassembly
^ If code P-1791(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 P-0736(50), P-0715(56), or P-0720(57)
^ Solenoid/TRS assembly - may also set codes P-1732(90) and/or P-1726(BO)
^ Failed or intermittent slipping UD clutch may also set codes P-0731(51) and/or P-0732(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 P-0715(56) and P-0720(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 P-1794(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 P-1799(74)
^ TCM

Name of Code:
P-1715(65) - Restricted Port in T3 Range

When Monitored: Whenever the Engine is running and the Manual valve is in the T3 range.

Set Condition: The code is set if the conditions for a code 47 are present with the manual valve is in the T3 range.

Theory of Operation: The conditions to set a DTC 47 are easily satisfied while in the T3 range. There is no problem with the transmission itself if this code is set.

Transmission Effects: The transmission will go into neutral when this code is set. If the driver puts the shifter in neutral and back to drive, the transmission will operate normally.

Possible Causes:
^ Manual linkage out of adjustment, causing T3 range while shifter is in OD.
^ Driver resting hand on shift lever while driving, causing T3 range.

Name of Code:
P-1799(74) - Temperature Sensor

When Monitored: Whenever the Engine is running.

Set Condition: The code is set if any of the following conditions exist for three consecutive key starts:
^ The Temperature Sensor voltage is out of range (below 0.07 volts or greater than 4.94 volts)
^ If continuous erratic Temperature Sensor voltage is sensed.
^ The Temperature Sensor temperature stays below 80° for an extended period of time.

Theory of Operation: The TCM uses a Temperature Sensor to monitor the transmission's sump temperature. This temperature is used to determine which shift schedule the TCM is to use. If the Temperature Sensor circuit fails to operate properly the TCM will use the calculated oil temperature routine found in prior model year TCM's. If this occurs for three consecutive key starts, the code will be set. The TCM will then test the Temperature Sensor circuit after every 35th OBDII warm-up start. If the Temperature Sensor circuit is OK, the Temperature Sensor data is used in place of the Calculated Oil Temperature Routine.

Transmission Effects: If the Temperature Sensor indicates a temperature below 0° or above 240° at start up, the TCM compares the calculated oil temperature to the indicated oil temperature. If the calculated oil temperature differs significantly from the Temperature Sensor value, the calculated oil temperature will be used for that key start. This code does not cause the transmission to go into limp-in mode.

Possible Causes:
^ Transmission temperature sensor signal circuit short to ground, short to voltage, or open circuit.
^ Speed sensor ground circuit short to ground, short to voltage, or open circuit.
^ Temperature Sensor
^ TCM

Name of Code:
P-1738(75) - High Temperature Operation Activated

When Monitored: Whenever the engine is running.

Set Condition: Immediately when the Overheat shift schedule is activated.

Theory of Operation: If the transmission oil temperature rises above 240°, the overheat shift schedule is activated (See Transmission Operation as a function of Transmission Oil Temperature) and the fault code is set. The code is an information fault code only and is being set to aid the technician in determining root cause of a customer driveability issue. The code is also intended to alert the technician to determine if a cooling system malfunction has occurred or if an additional transmission air to oil cooler should be added to the vehicle if the customer regularly drives in a manner that overheats the transmission. Extended operation above 240° will reduce the durability of the transmission and should be avoided. Correcting the cooling system malfunction or installing an additional transmission oil cooler will improve transmission durability especially for customers who operate in city/construction stop and go traffic, tow trailers regularly, drive aggressively in low gear or drive regularly in mountainous areas.

Transmission Effects: Information only code. Overheat shift schedule was activated, no limp-in condition occurs. See description of overheat shift schedule.

Possible Causes:
^ Transmission Overfilled with Oil
^ Engine cooling fan failure
^ Engine thermostat stuck closed
^ Radiator corroded or packed with dirt
^ Transmission cooler corroded or packed with dirt
^ Transmission Oil Cooler Plugged
^ Customer driving pattern requires additional transmission cooling (See Theory of Operation for driving patterns that can cause overheating)

Name Of Code:
P-1739(76) - Power-Up a Speed

When Monitored: When TCM (Transmission Control Module) initially powers-up.

Set Condition: If the TCM powers up and senses a valid forward gear PRNDL code and the output RPM is above 800 RPM (approx. 20 MPH) the code will be set.

Theory of Operation: If a vehicle loses power to the TCM, the solenoids will go to their respective power off state. Some solenoids are normally vented and some are normally applied in their power off state. The transmission is designed to be in 3 d gear with all of the solenoids in this state. However, if power is restored, the TCM will power-up and normal operation will be restored.
This code identifies that power to the TCM was restored when the gear selector was in a "Drive" position while the vehicle was moving at speeds above 20 MPH. This code does not indicate a problem with the transmission or TCM, instead, it suggests intermittent problems in the fused ignition switch output, fused B(+), or ground circuits to the TCM. Alternately, if a person performs a rolling restart maneuver, the code can be set. Therefore it is critical that this DTC be investigated if the vehicle is experiencing intermittent 3rd gear operation and a subsequent return to normal operation.

Transmission Effects: No limp-in, although the symptom might be described as an intermittent limp-in. Code is for information only when trying to diagnosis intermittent 3rd gear operation and a subsequent return to normal operation.

Possible Causes:
^ No Problem if vehicle is started in "neutral" at speeds above 20 MPH and shifted quickly to a forward gear position.
^ Quick key off then on while driving is any forward gear.
FOR INTERMITTENT 3rd GEAR OPERATION AND THEN A SUBSEQUENT RETURN TO NORMAL OPERATION WITHOUT CYCLING THE IGNITION KEY
^ Intermittent Direct Battery (Fused B(+)) connection between TCM (60-way pin 56) and battery.
^ Intermittent Fused Ignition Switch Output between TCM (60-way pin 11) and ignition switch.
^ Intermittent Ground to TCM (60 way pins 53 and 57).

Name of Code:
P-1765(80) - Switched Battery

When Monitored: Ignition key is turned from "off" position to "run" position and/or ignition key is turned from "crank" position to "run" position.

Set Condition: This code is set if the Transmission Control Module (TCM) senses voltage on any of the pressure switch inputs prior to the TCM energizing the relay.

Theory of Operation: The Transmission control relay is used to supply power to the solenoids and pressure switches when the transmission is in normal operating mode. When the relay is off, no power is supplied and the transmission is in "limp-in" mode. The relay output is fed back to the TCM through pins 16, 17 and 38. It is referred to as 1ransmission Control Relay Output".
Immediately after a controller reset (ignition key turned to the "run" position or after cranking engine), the TCM verifies that the relay contacts are open by checking for no voltage at the transmission control relay output terminals. After this is verified, the voltage at the pressure switches is checked. There should be no voltage on the pressure switches at this time. The TCM will then activate the relay.

Transmission Effects: The MIL will illuminate and the transmission system will default to the Immediate Shutdown routine.

Possible Causes:
^ Short to battery on one or more pressure switch sense circuits.
^ TCM connector problems.
^ Solenoid/TRS connector problems.
^ TCM.

Name of Code:
P-1784(81) - LR Pressure Switch Circuit
P-1734(82) - 2C Pressure Switch Circuit
P-1781(84) - OD Pressure Switch Circuit
P-1733(88) - 4C Pressure Switch Circuit
P-1732(90) - UD Pressure Switch Circuit

When Monitored: Whenever the engine is running.

Set Condition: The appropriate code is set if one of the pressure switches are open or closed at the wrong time in a given gear (see image).

Theory of Operation: The Transmission system uses five pressure switches to monitor the fluid pressure in the LR, 2C, 4C, UD, and OD clutch circuits. The pressure switches are continuously monitored for the correct states in each gear as shown in image.

Normal Pressure Switch States:

Normal Pressure Switch States

Transmission Effects: The MIL will illuminate and the transmission system will default to the Immediate shutdown routine.

Possible Causes:
^ If code P-1791(35) is present, perform code P-1791(35) diagnostic procedures
^ Pressure switch sense circuit open or shorted to ground between TCM and Solenoid/TRS assembly
^ Pressure switch sense circuit shorted to battery
^ Pressure switch
^ Loose valve body bolts
^ Plugged filter - internal transmission or torque converter failure
^ Ball check not seating.
^ Solenoid malfunction (If set with corresponding Solenoid DTC. i.e.: 2C Pressure switch set with 2C solenoid)
^ Oil Pump (Code P-1784(81) only)
^ TCM

Name of code:
P-1728(A2) - 2C Hydraulic Pressure Test Failure
P-1787(A4) - OD Hydraulic Pressure Test Failure
P-1727(A8) - 4C Hydraulic Pressure Test Failure
P-1726(BO) - UD Hydraulic Pressure Test Failure

When Monitored: In any forward gear with engine speed above 1000 RPM shortly after a shift and every minute thereafter.

Set Condition: Immediately after a shift into a forward gear, with engine speed above 1000 RPM, the TCM momentarily turns on element pressure to the clutch circuits that do not have pressure to identify that the appropriate pressure switch closes. If the pressure switch does not close it is tested again. If the switch does not close the second time, the appropriate code is set.

Theory of Operation: The Transmission. Control Module (TCM) tests the pressure switches when they are off. The test verifies that the switches are operational (They will close with pressure applied). The TCM verifies that the switch closes when the corresponding element is applied. If a switch fails to close, it is retested. If it fails the second test, the code is set.

Transmission Effects: The MIL will illuminate and the transmission system will default to the orderly Shutdown routine.

Possible Causes:
^ Pressure switch sense circuit shorted to battery between TCM and solenoid/TRS assembly.
^ Solenoid malfunction (If set with corresponding Solenoid DTC. i.e.: 2C Hydraulic Pressure switch set with 2C solenoid)
^ Low oil pressure
^ Pressure switch

Name of code:
P-0750(C1) - LR Solenoid Circuit
P-0755(C2) - 2C Solenoid Circuit
P-0760(C3) - OD Solenoid Circuit
P-0770(C4) - 4C Solenoid Circuit
P-0765(C5) - UD Solenoid Circuit
P-1737(C6) - MS Solenoid Circuit

When Monitored: Initially at power-up, then every 10 seconds thereafter. They will also be tested immediately after a gear ratio or pressure switch error is detected.

Set Condition: Three consecutive solenoid continuity test failures, or one failure if test is run in response to a gear ratio or pressure switch error.

Theory of Operation: Six solenoids are used to control the friction elements (clutches). The continuity of the solenoid circuits are periodically tested. Each inactive solenoid is turned on for a few milliseconds, then off. Each active solenoid is turned off for a few milliseconds, then on. This pulsing of voltage to the solenoid causes an inductive spike which can be sensed by the TCM. If an inductive spike is not sensed by the Transmission Control Module (TCM) during the continuity check, it is tested again. If the test fails three consecutive Times, the appropriate code is set. If the solenoid test is run in response to a gear ratio or pressure switch error, one failure will result in setting the appropriate code.

Transmission Effects: The MIL will illuminate and the transmission system will default to the Immediate Shutdown routine.

Possible Causes:
^ Open or shorted solenoid circuit(s) between TCM and solenoid/TRS assembly.
^ Open ground circuit.
^ TCM connector problems.
^ Solenoid/TRS, connector problem.
^ Solenoid/TRS, assembly.
^ TCM.

Name of Code:
P-1720(C8) - Line Pressure Error
P-1722(C9) - Line Pressure Low
P-1724(CB) - Line Pressure Hi

When Monitored: Continuously with engine running.

Set Condition: The TCM has an internal error counter for each DTC above. When any of the counters reaches a preset threshold, the appropriate code is set.

Theory of Operation: Line pressure is controlled by the TCM. It is measured by the Line Pressure Sensor (LPS) and regulation is achieved by changing the duty cycle of the Pressure Control Solenoid (PCS). (0% duty cycle = solenoid off = max line pressure, 100% duty cycle = solenoid on = min line pressure). The TCM calculates the desired line pressure based on inputs from the transmission and engine. The TCM calculates torque input to the transmission and uses it as the primary input to the desired line pressure calculation. This is called Torque Based Line Pressure. In addition, the line pressure is set to a preset level (100 or 120 PSI) during shifts and in Park and Neutral to ensure consistent shift quality. The desired line pressure is continuously being compared to the actual line pressure. If the actual line pressure is consistently higher than the target, the line pressure high DTC P-1724(CB) will be set. If the actual line pressure is consistently lower than the target, the line pressure low DTC P-1722(C9) will be set. If it is consistently out of range, but not consistently high or low, it is considered out of range and the line pressure error DTC P-1720(C8) will be set.

Transmission Effects: The MIL will illuminate. The Transmission system will default to open loop line pressure control resulting in a fixed PCS duty cycle. This duty cycle will change slightly depending on temperature and current gear.

Possible Causes:
^ Sticking Regulator Valve
^ Pressure Control Solenoid
^ Line Pressure Sensor
^ Oil pump
^ Plugged Filter
^ 5V supply circuit to Line Pressure Sensor open (Sensor reading will read a constant value between 85 and 95 PSI).
^ TCM.

Name of Code:
P-1721(CA) - Line Pressure Sensor Error

When Monitored: Continuously with engine running.

Set Condition: If the Line Pressure Sensor (LPS) voltage is below 0.2 volts or above 4.75 volts the code will be set.

Theory of Operation: Line pressured is controlled by the TCM. It is measured by the LPS and regulation is achieved by changing the duty cycle of the Pressure Control Solenoid (PCS) (0% duty cycle = solenoid off max line pressure, 100% duty cycle = solenoid on min line pressure). This sensor is continuously checked for out of range voltage by the TCM.

Transmission Effects: The MIL will illuminate. The Transmission system will default to open loop line pressure control resulting in a fixed PCS duty cycle. This duty cycle will change slightly depending on temperature and current gear.

Possible Causes:
^ LPS signal circuit shorted to ground, shorted to voltage, or open.
^ 5-volt supply circuit shorted to ground, shorted to voltage, or open.
^ Open sensor ground.
^ Line Pressure Sensor.