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DTC DESCRIPTIONSName of code: P0700 (12) - Battery was Disconnected (Informational code Only)
When monitored: Whenever the key is in the Run/Start position.
Set condition: This code is set whenever the Transmission Control Module (TCM) is disconnected from battery power (B+) or ground. It will also be set during the DRBIII Battery Disconnect procedure.
Theory of operation: A battery backed RAM (Random Access Memory) is used to maintain some learned values. When the battery B(+) is disconnected, the memory is lost. When the B(+) is restored, this memory loss is detected by the TCM. The code is set and the learned values are initialized to known constants or previously learned values from EEPROM (Electronic Erasable Programmable Read Only Memory). This results in the initialization of some parameters.
Transmission Effects: Loss of trouble code data. Immediate limp-in mode if power is lost while operating the vehicle. Normal operation is resumed if the power is restored during the same key start.
Possible causes:
> Battery voltage removed from TCM
> TCM disconnected
> Dead Battery
> Low battery voltage during cranking
> Battery Disconnect by DRBIII or MDS
> Bad TCM ground circuit
Name of code: P1767 (14) - Relay Output Always On
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 greater than 3 volts at the Trans Relay Output (switched battery) terminal of the TCM prior to the TCM energizing the relay.
Theory of operation: The transmission control relay is used to supply power to the solenoid pack when the transmission is in normal operating mode. When the relay is off, no power is supplied to the solenoid pack and the transmission is in limp-in mode. The relay output is fed back to the TCM through pins 16 and 17. It is referred to as the Trans Relay Output circuit or switched battery.
Transmission Effects: The MIL will illuminate and the transmission system defaults to Logical limp-in mode. Logical Limp-in mode results in the same modes of operation as Relay Open Limp-in. Since the relay is stuck "on", the TCM can not open the relay, and the TCM shifts to 2nd gear.
Possible causes:
> Relay failure (welded contacts).
> Short to battery in 12-volt supply and/or Transmission Control Relay Output circuit(s)
> Short to voltage
> TCM connector problems
> TCM
Name of code: P1768 (15) - Relay Output Always Off
When monitored: Continuously
Set condition: This code is set when less than 3 volts are present at the Trans Relay Output (switched battery) terminals at the Transmission Control Module (TCM) when the TCM is energizing the relay.
Theory of operation: The Transmission Control Relay is used to supply power to the solenoid pack when the transmission is in normal operating mode. When the relay is off, no power is supplied to the solenoid pack and the transmission is in limp-in mode. The relay output is fed back to the TCM through pins 16 and 17. It is referred to as the Trans Relay Output circuit or a switched battery.
After a controller reset (ignition key turned to the run position or after cranking engine), the controller energizes the relay. Prior to this the TCM verifies that the contacts are open by checking for no voltage at the switched battery terminals. After the relay is energized, the TCM monitors the terminals to verify that the voltage is greater than 3 volts.
Transmission Effects: The MIL illuminates and the transmission system will defaults to Relay Open limp-in mode.
Possible causes:
> Relay failure (intermittent relay function caused by oxidized or contaminated relay contacts)
> Short to ground or open circuit in the Transmission Control Relay output circuit(s)
> TCM connector problem
> TCM
Name of code: P0725 (18) - Engine Speed Sensor Circuit
When monitored: Whenever the engine is running.
Set condition: This code is set when the engine speed sensed by the Transmission Control Module (TCM) is less than 390 RPM or greater than 8000 RPM for more that 2.0 seconds.
Theory of operation: The TCM uses the Crank Sensor signal to calculate engine RPM. This signal is supplied by the PCM and uses a dedicated circuit called the EATX RPM Signal circuit. If the TCM interprets this signal to be out of range when the engine is running (as reported by the PCM over the bus) the code is set.
Transmission Effects: The MIL illuminates and the transmission system defaults to Relay Open limp-in mode.
Possible causes:
> Open or short in EATX RPM Signal circuit
> TCM and/or PCM connector problems
> TCM
> PCM
Name of code: P0716 (19) - Bus Communication with Engine Module
When monitored: Continuously with key on.
Set condition: If no PCI bus messages are received from the Powertrain Control Module (PCM) for 10 seconds.
Theory of operation: The TCM communicates with the PCM using the PCI bus. It relies on certain information to function properly. The TCM continuously monitors PCI bus to check for messages broadcast from the PCM.
Transmission Effects: Delayed 3-4 shifts. No EMCC and early 3-4 shifts for a few minutes after engine is started.
Possible causes:
> Open or shorted PCI bus circuit
> TCM
> PCM
Name of code: P1765 (20) - 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 solenoid pack when the transmission is in normal operating mode. When the relay is off, no power is supplied to the solenoid pack and the transmission is in a limp-in mode. The relay output is fed back to the TCM through pins 16 and 17. It is referred to as the Trans Relay Output circuit or a switched battery.
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 switched battery terminals. After this is verified, the voltage at the Solenoid Pack 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 illuminates and the transmission system defaults to Relay Open limp-in mode.
Possible causes:
> Short to battery on one or more pressure switch sense circuits
> TCM connector problems
> TCM
Name of code: P1781 (21) - OD Pressure Switch Sense Circuit
When monitored: Whenever the engine is running.
Set condition: This code is set if the OD pressure switch is open or closed at the wrong time in a given gear (see chart below).
Theory of operation: The Transmission system uses three pressure switches to monitor the fluid pressure in the L-R, 2-4, and OD clutch circuits. The pressure switches are continuously monitored for the correct states in each gear as shown below.
Normal Pressure Switch States
Transmission Effects: Normal operation will be experienced if no other codes are present. TCM will ignore the code. Limp-in condition will only occur if code P-1781(21) is present with a code P-0706 (28).
Possible causes:
> If code P-1791 (35) is present, ignore code P-1781(21) and perform code P-1791 diagnostic procedures
> 0D pressure switch sense circuit open or shorted to ground between TCM and solenoid pack
> 0D pressure switch sense circuit short to battery
> Solenoid pack
> Loose valve body bolts
> Plugged filter - internal transmission or torque converter failure
> TCM
Name of code: P1782 (22) - 2-4 Pressure Switch Sense Circuit
When monitored: Whenever the engine is running.
Set condition: This code is set if the 2-4 pressure switch is open or closed at the wrong time in a given gear (see chart below).
Theory of operation: The Transmission system uses three pressure switches to monitor the fluid pressure in the L-R, 2-4, and OD elements. The pressure switches are continuously monitored for the correct states in each gear as shown below.
Normal Pressure Switch States
Transmission Effects: If the 2-4 pressure switch is identified as closed in P or N. the code will immediately be set and normal operation will be allowed for that given key start. If the problem is identified for 3 successive key starts, the transmission will go into relay open limp-in mode.
If the 2-4 pressure switch is identified as being closed in 1st or 3rd gear and was not identified as being closed in P or N. then 2nd gear or 4th gear will be substituted for 1st or 3rd gear depending on throttle angle and vehicle speed. A short period of time after the gear substitution, the transmission will return to normal operating mode. If the transmission is shifted back into 1st or 3rd gear through normal operation, and the 2-4 pressure switch remains closed, 2nd or 4th gear will be substituted briefly and then resume normal operation. If four gear substitutions occur in a given key start, the transmission will go into relay open limp-in mode.
If the 2-4 pressure switch is open (indicating no 2-4 clutch pressure) in 2nd or 4th gear, the TCM sets code P-1782 (22) and continues with normal operation. The transmission will only go into relay open limp-in mode if a code P-0705 (28) is also present. If no 2-4 clutch pressure is present a speed ratio code P-0732 (52) or P-0734 (54) will be set and cause the limp-in condition.
Possible causes:
> If code P-1791 (35) is present, ignore code P-1782 (22) and perform code P-1791 diagnostic procedures
> 2-4 pressure switch sense circuit open or shorted to ground between TCM and solenoid pack
> 2-4 pressure switch sense circuit shorted to battery
> Solenoid pack
> Transmission overheated - Excessive regulator valve leakage in the valve body causing high line pressure which results in 2-4 solenoid blow-off in 1st or 3rd gear. May require new valve body if it happens only when hot.
> Loose valve body bolts
> Plugged filter - internal transmission or torque converter failure
> TCM
Name of code: P1784 (24) - L-R Pressure Switch Sense Circuit
When monitored: Whenever the engine is running.
Set condition: This code is set if the L-R pressure switch is either open or closed at the wrong time in a given gear.
Theory of operation: The Transmission system uses three pressure switches to monitor the fluid pressure in the L-R, 2-4, and OD elements. The pressure switches are continuously monitored for the correct states in each gear as shown below.
Normal Pressure Switch States
Transmission Effects: If a set condition is identified, 1st gear and torque converter lock-up (EMCC) will be inhibited. The vehicle will launch in 2nd gear and shift normally through the gears without allowing EMCC. If during the same key start, the set condition is no longer valid, the transmission will return to normal operation (1st and EMCC available). A relay open limp-in will not occur unless code P-1784 (24) is accompanied by a code P-0705 (28).
Possible causes:
> If code P-1791 (35) is present, ignore code P-1784 (24) and perform code P-1791 (35) diagnostic procedures
> L-R pressure switch sense circuit open or shorted to ground between TCM and solenoid pack
> L-R pressure switch sense circuit shorted to battery
> Solenoid pack
> Valve body - solenoid switch valve stuck in LU position. May be accompanied by a code P1775 (37)
> Loose valve body bolts
> Plugged filter - internal transmission or torque converter failure
> TCM
Name of code: P0705 (28) - Check Shifter Signal
When monitored: Continuously with the key on.
Set condition: 3 occurrences in one key start of an invalid PRNDL code, which lasts for more than 0.1 second.
Theory of operation: The C1 through C4 (T1, T3, T41, and T42) sense circuits communicate the shift lever position to the TCM. Each circuit is terminated at the transmission with a switch. Each switch can be either open or closed, depending on the shift lever position. The TCM can decode this
Transmission Effects and possible causes:
Scenario 1) - All PRNDL lights stay illuminated indefinitely in Park following a Key start.
> Wrong Part Number TCM for application
> TRS connector not plugged in
> C1 through C4 (T1, T3, T41, or T42) circuits are either open, shorted to ground, or shorted to 12 volts.
> PCI bus failure (Open or shorted resulting in no communication to BCM or Cluster)
> TRS
> TCM
> BCM
Scenario 2) - "P" is indicated following a key start but all PRNDL lights illuminate in "N" following a shift from "R" to "N". If PRNDL lights illuminate in "N" and shifter is moved directly into "3" or "L" position without pausing in "OD", then the "OD" position shift schedule and electronic display will indicate "OD" until the shifter is shifted into the "OD" position and held for at least 3 seconds.
> Worn Manual Lever (Rooster Comb). Check for heavy wearing by TRS switch contacts
> Intermittent C1 through C4 (T1, T3, T41 or T42) circuits. Check for corrosion, terminal push-outs or spread terminals at 60-way and/or TRS switch 10-way connector
> TRS
> TCM
> BCM
Scenario 3) - If the invalid code happened while operating in the "3" or "L" position, then the "3" or "L" shift schedule and electronic display will be frozen (regardless of whether "OD", "3" or "L" is selected) until the shifter is moved to the "N" information and determine the shift lever position. Each shift lever position has a certain combination of switches, which will be open and closed, this is called a PRNDL code. There are 4 switches, therefore: there are many possible combinations of open and closed switches (codes). However, there are only 9 valid codes (8 for Autostick), one for each gear position and three recognized between gear codes. The remainder of the codes should never occur, these are called invalid codes. The following chart shows the normal switch states for each shift lever transition. Position (all PRNDL lights will illuminate) and then back to the "OD" position and held there for at least 3 seconds in order to resume the normal "OD" shift schedule and electronic display.
> Intermittent C1 through C4 (T1, T3, T41 or T42) circuits. Check for corrosion, terminal push-outs or spread terminals at 60-way and/or TRS connector
> TRS
> TCM
> BCM
These same symptoms may occur without the code P-0705 (28) getting set. It is possible that the invalid code that was sensed by the TCM only occurred once or twice during the given ignition key start and/or did not last for longer than 0.1 second.
Name of code: P-0120 (29) - Throttle Position Sensor Signal
When monitored: Whenever the engine is running.
Set condition: This code is set if the throttle angle goes out of range or if throttle angle changes abruptly (de: faster than the throttle body motion could occur)
Theory of operation: The Transmission Control Module (TCM) receives the throttle position signal from the Throttle Position Sensor (TPS) through a wire spliced into the TPS circuit to the PCM. The TPS has a 5-volt pull up supplied from the Powertrain Control Module (PCM). The signal is checked for out-of-range as well as an intermittent (excessive signal changes).
Transmission Effects: Extremely erratic transmission shifting with an intermittent TPS signal just prior to setting the code. If the intermittent does not last long enough to set the code, the customer will say that the transmission violently hunts between gears. The TCM will use a calculate throttle angle supplied by the PCM over the PCI bus. If the PCI bus is unavailable, the TCM will use a default throttle angle of 24 degrees for the key start in which the code was set. The TCM will try to use the TPS signal again on the next key start.
Possible causes:
> Open or shorted TPS signal and/or ground circuits
> TCM connector problems
> TPS or TPS connector (Check PCM DTC's)
> PCM
> TCM
Name of code: P-1787 (31) - OD Hydraulic Pressure Test Failure
P-1788 (32) - 2-4 Hydraulic Pressure Test Failure
P-1789 (33) - OD/2-4 Hydraulic Pressure Test Failure
When monitored: In 1st, 2nd, or 3rd gear with engine speed above 1000 RPM shortly after a shift and every minute thereafter.
Set Condition: Immediately after a shift into 1st, 2nd, or 3rd gear, with engine speed above 1000 RPM, the TCM momentarily turns on element pressure to the 2-4 and/or OD clutch circuits 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 OD and 2-4 pressure switches when they are off (OD and 2-4 are tested in 1st gear, OD in 2nd gear, and 2-4 in 3rd gear). The test verifies that the switches are operational. 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 illuminates and the transmission system defaults to Relay Open limp-in mode.
Possible causes:
> Pressure switch sense circuit shorted to battery between TCM and solenoid pack.
> Low line pressure
> Solenoid Pack
Name of code: P-1791 (35) - Loss of Prime
When monitored: If the transmission is slipping in any forward gear and the pressure switches are not indicating pressure, a lost of prime test is run.
Set condition: If the transmission begins to slip in any forward gear, and the pressure switch or switches that should be closed for a given gear are open, a loss of prime test begins. All available elements (in 1st gear L-R, 2-4 and OD, in 2nd, 3rd, and 4th gear 2-4 and OD) are turned on by the
Transmission Control Module (TCM) to see if pump prime exists. The code is set if none of the pressure switches respond. The TCM will continue to run the loss of prime test until pump pressure returns.
Theory of operation: The loss of prime test is used to prevent transmission defaults, which can be caused by a lack of pump prime.
Transmission Effects: Vehicle will not move or transmission slips. Normal operation will continue if pump prime returns.
Possible causes:
> Low transmission fluid level
> PRNDL indicates a valid OD code in the hydraulic reverse position
> Transmission fluid filter clogged or damaged
> Transmission fluid filter improperly installed (Bolts loose or O-ring missing)
> Oil pump - If a customer has a problem when the transmission is cold whereby he shifts to reverse, gets reverse, and then shifts to OD and does not get OD (gets a neutral condition), and then can not get reverse or OD for between 3 - 20 seconds, replace the oil pump. High side clearance in the oil pump will set a code 35. The pump will prime upon start-up, but as the torque converter purges air (drain down) the air will leak across the inner rotor into the pump suction port and cause a loss of prime right after the shift into OD. After 3 - 20 seconds, pump prime will return and normal operation will continue. The pump should be replaced only after all other possible causes above have been checked and verified.
Name of code: P-1790 (36) - Fault Immediately After Shift
When monitored: After a gear ratio error is stored
Set condition: This code is set if the associated gear ratio code is stored within 1.3 seconds after a shift.
Theory of operation: This code will only be stored along with a 50 series code. If this code is set, it indicates the problem is mechanical in nature. When this code exists, diagnosing the transmission should be based on the associated gear ratio code and primarily mechanical causes should be considered.
Transmission Effects: None
Possible causes:
> Mechanical causes as listed under associated gear ratio code.
Name of code: P-1775 (37) - Solenoid Switch Valve Latched in TCC Position
When monitored: During an attempted shift into 1st gear.
Set condition: This code is set if three unsuccessful attempts are made to get into 1st gear in one given key start
Theory of operation: The solenoid switch valve (SSV) controls the direction of the transmission fluid when the L-R TCC solenoid is energized. The SSV will be in the downshifted position in 1st gear, thus directing the fluid to the L-R clutch circuit. In 2nd, 3rd, and 4th, it will be in the upshifted position and directs the fluid into the torque converter clutch (TCC).
When shifting into 1st gear, a special hydraulic sequence is performed to ensure SSV movement into the downshifted position. The L-R pressure switch is monitored to confirm SSV movement. If movement is not confirmed (the L-R pressure switch does not close), 2nd gear is substituted for 1st.
Transmission Effects: Transmission will have no 1st gear (2nd gear will be substituted), and no EMCC operation.
Possible causes:
> PRNDL indicates a valid OD code in the hydraulic reverse position
> Valve body - Solenoid valve stuck in TCC position
> High idle speed
> Solenoid malfunction - L-R pressure switch will not close
> L-R Pressure Switch Sense circuit shorted to battery
Name of code: P-0740 (38) - Torque Converter Clutch Control Circuit
When monitored: During Electronically Modulated Converter Clutch (EMCC)
Set Condition:
a) The transmission must be in EMCC, with the input speed greater than 1750 RPM. The TCC/L-R solenoid must achieve its maximum duty cycle and still not be able to pull the engine speed within 60 RPM of input speed.
b) If the transmission is in FEMCC and the engine can slip the TCC by more than 100 RPM (Engine speed - Input speed) for 10 seconds.
The code will be set if one of these events happens three times at a throttle angle less than 30 degrees.
Theory of operation: When in 2nd, 3rd, or 4th gear, the torque converter clutch (TCC) can be locked when certain conditions are met. The TCC piston is electronically modulated by increasing the duty cycle of the L-R/TCC solenoid until the torque converter slip difference (difference between engine and turbine speed) is within 60 RPM. Then the L-R/TCC solenoid is fully energized (FEMCC 1 100% duty cycle). Torque converter slip is monitored in FEMCC to ensure adequate clutch capacity.
Transmission Effects: EMCC will still be available after code is set. MIL will illuminate after minutes of accumulated slip in FEMCC. The transmission will attempt normal operation (no limp-in) even after the MIL is illuminated.
Possible causes:
> Worn pump bushing and/or failed torque converter - both should be replaced during a rebuild with code P0740 (38) present
> Solenoid pack.