Theory of operation:
The PCM is constantly monitoring it's internal processor. If an internal problem is detected, this DTC will be set. This DTC can also be set by a bad ground to the PCM and/or Trans Control Relay.
Transmission Effects: The MIL will illuminate (this DTC can take up to five minutes of problem identification before illuminating the MIL) and the transmission system will default to the Immediate Shutdown routine.
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 PCM. 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.
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 PCM. 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 Limp-in. Since the relay is stuck "on", the PCM can not open the relay, and the PCM shifts to 2nd gear.
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 PCM. It is referred to as the Trans Relay Output circuit or 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 PCM verifies that the contacts are open by checking for no voltage at the switched battery terminals. After the relay is energized, the PCM monitors the terminals to verify that the voltage is greater than 3 volts.
Transmission Effects: The MIL illuminates and the transmission system defaults to Limp-in mode.
The PCM uses a new dual port RAM internal to the controller to send the Crank Sensor signal to the Transmission Control System. If the PCM interprets this signal to be out of range when the engine is running the code is set.
Transmission Effects: The MIL illuminates and the transmission system defaults to Limp-in mode.
The Transmission Control System communicates with the engine control system using the PCI bus. It relies on certain information to function properly. The Transmission Control System continuously monitors the PCI bus to check for messages broadcast from the engine control system.
Transmission Effects: Delayed 3-4 shifts. No EMCC and early 3-4 shifts for a few minutes after engine is started.
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 PCM. 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 PCM 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 PCM will then activate the relay.
Transmission Effects: The MIL illuminates and the transmission system defaults to Limp-in mode.
The Transmission system uses three pressure switches to monitor the fluid pressure in the LR, 2/4, and OD clutch circuits. The pressure switches are continuously monitored for the correct states in each gear as shown below.
| SWITCHES | R | N | 1ST | 2ND | 3RD | 4TH |
|---|---|---|---|---|---|---|
| L/R | OPEN | CLOSED | CLOSED | OPEN | OPEN | OPEN |
| 2/4 | OPEN | OPEN | OPEN | CLOSED | OPEN | CLOSED |
| O/D | OPEN | OPEN | OPEN | OPEN | CLOSED | CLOSED |
Transmission Effects: Normal operation will be experienced if no other codes are present. PCM will ignore the code. Limp-in condition will only occur if code P0871(21) is present with a code P0706(28).
The Transmission system uses three pressure switches to monitor the fluid pressure in the LR, 2/4, and OD elements. The pressure switches are continuously monitored for the correct states in each gear as shown below.
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 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 Limp-in mode.
| SWITCHES | R | N | 1ST | 2ND | 3RD | 4TH |
|---|---|---|---|---|---|---|
| L/R | OPEN | CLOSED | CLOSED | OPEN | OPEN | OPEN |
| 2/4 | OPEN | OPEN | OPEN | CLOSED | OPEN | CLOSED |
| O/D | OPEN | OPEN | OPEN | OPEN | CLOSED | CLOSED |
If the 2/4 pressure switch is open (indicating no 2/4 clutch pressure) in 2nd or 4th gear, the PCM sets code P0846(22) and continues with normal operation. The transmission will only go into Limp-in mode if a code P0706(28) is also present. If no 2/4 clutch pressure is present a gear ratio code P0732(52) or P0734(54) will be set and cause the limp-in condition.
The Transmission system uses three pressure switches to monitor the fluid pressure in the LR, 2/4, and OD elements. The pressure switches are continuously monitored for the correct states in each gear as shown below.
| SWITCHES | R | N | 1ST | 2ND | 3RD | 4TH |
|---|---|---|---|---|---|---|
| L/R | OPEN | CLOSED | CLOSED | OPEN | OPEN | OPEN |
| 2/4 | OPEN | OPEN | OPEN | CLOSED | OPEN | CLOSED |
| O/D | OPEN | OPEN | OPEN | OPEN | CLOSED | CLOSED |
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). Limp-in will not occur unless code P0841(24) is accompanied by a code P0706(28) and the MIL will illuminate after 5 minutes of substituted operation.
The C1 through C4 (T1, T3, T41, and T42) sense circuits communicate the shift lever position to the PCM. 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 PCM can decode this 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 position.
| TRS | Park | T1 | Rev | T2 | N | T2 | OD | T3 | 3/AS | T3 | L |
|---|---|---|---|---|---|---|---|---|---|---|---|
| T1 (C4) | OP | OP | OP | CL | CL | CL | CL | CL | OP | CL | CL |
| T3 (C3) | CL | CL | OP | OP | OP | OP | OP | CL | CL | CL | CL |
| T41 (C1) | CL | OP | OP | OP | CL | OP | OP | OP | OP | OP | OP |
| T42 (C2) | CL | CL | CL | CL | CL | CL | OP | OP | OP | OP | CL |
The following are DRBIII® reported Shift Lever Error Codes (chart)
| ERROR CODE | SWITCH STUCK | POSITION |
|---|---|---|
| 1 | T1/C4 STUCK | OPEN |
| 2 | T1/C4 STUCK | CLOSED |
| 3 | T3/C3 STUCK | OPEN |
| 4 | T3/C3 STUCK | CLOSED |
| 5 | T42/C2 STUCK | OPEN |
| 6 | T24/C2 STUCK | CLOSED |
| 7 | T41/C1 STUCK | OPEN |
| 8 | T41/C1 STUCK | CLOSED |
The transmission controller receives the throttle position signal and its ground from the Throttle Position Sensor (TPS). The TPS has a 5 volt pull up supplied by the engine controller. The throttle signal is checked for out-of-range as well as intermittency (excessive signal changes). The engine controller transmits the throttle value via the Dual Port RAM. Most engine controllers can synthesize the throttle value if the throttle position sensor signal is lost. If a throttle error is detected by the transmission controller and the throttle value is available via the Dual Port RAM, the Dual Port RAM throttle value will be used and normal operation will continue, however a throttle fault code will be set. If a throttle error is detected and the throttle value is not available via the Dual Port RAM, normal operation will be discontinued, a throttle fault code will be set, and the MIL will be turned on after 5 min. of substituted operation.
Transmission Effects:
- If throttle value available via the Dual Port RAM - No effect.
- If throttle value not available via the Dual Port RAM
A default throttle value is used.
Torque converter lock-up inhibited.
4th gear inhibited.
Limited shift schedule.
MIL on after 5 min. of substituted operation.
The Transmission Control System 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 PCM 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 Limp-in mode.
The loss of prime test is used to prevent transmission faults, 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.
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
Name of code: P1775(37) - Solenoid Switch Valve Latched in TCC Position
The solenoid switch valve (SSV) controls the direction of the transmission fluid when the LR/TCC solenoid is energized. The SSV will be in the downshifted position in 1st gear, thus directing the fluid to the LR 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 LR pressure switch is monitored to confirm SSV movement. If movement is not confirmed (the LR 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 and the MIL will illuminate after 5 minutes of substituted 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 LR/TCC solenoid until the torque converter slip difference (difference between engine and turbine speed) is within 60 RPM. Then the LR/TCC solenoid is fully energized (FEMCC/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 5 minutes of accumulated slip in FEMCC. The transmission will attempt normal operation (not in Limp-in) even after the MIL is illuminated.
Four solenoids are used to control the friction elements (clutches). The continuity of the solenoids circuits are periodically tested. Each solenoid is turned on or off depending on it's current state. An inductive spike should be detected by the PCM during this test. If no spike is detected, the circuit is tested again to verify the failure. In addition to the periodic testing, the solenoid circuits are tested if a gear ratio or pressure switch error occurs. In this case, one failure will result in the appropriate code being set.
Transmission Effects: The MIL will illuminate and the transmission goes into neutral if code is set above 35 Km/h (22 MPH), Limp-in mode when vehicle speed is below 35 Km/h (22 MPH).
The solenoid switch valve (SSV) controls the direction of the transmission fluid when the LR/TCC solenoid is energized. SSV will be in the downshifted position in 1st gear, thus directing the fluid to the LR clutch circuits. In 2nd, 3rd, and 4th, the SSV will be in the upshifted position and directs the fluid into the torque converter clutch (TCC).
When doing PEMCC or FEMCC, the LR pressure switch should indicate no pressure if the SSV is in the TCC position. If the LR pressure switch indicates pressure while in PEMCC or FEMCC, EMCC operation is aborted and inhibited to avoid inadvertent application of the LR clutch. Partial EMCC will be attempted if the LR pressure switch does not indicate pressure. A second detection of LR pressure results in setting the code.
Transmission Effects: At speeds above 72 Km/h (45 MPH), EMCC is inhibited. Once speed falls below 72 Km/h (45 MPH), the transmission will go into Limp-in mode and the MIL will illuminate after 5 minutes of substituted 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:
- 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 54).
- An excessive change in input or output speeds indicating signal intermittent will result in codes 56 and/or 57 being set.
- After a PCM reset in neutral, observing erratic output and input speed sensor signals indicates a loss of the common speed sensors ground. This sets a code 58.
Transmission Effects: The transmission will not go into Limp-in mode until three gear ratio error events occur in a given key start also the MIL will illuminate after 5 minutes of substituted operation. This allows for intermittent problems to correct themselves without opening the relay. However, if a gear ratio error develops, a code is always set, but if the condition corrects itself the transmission will continue without requiring the ignition key to be cycled on and off. Many different events could occur given the range of failures possible for codes 50 through 58. The following are a few examples:
- Codes 51, 52, 53, 54, 56, and 57 at speeds above 72 Km/h (45 MPH) - The appropriate code is set, EMCC is aborted and current gear is maintained. If while still traveling above 72 Km/h (45 MPH), the gear ratio becomes valid again, EMCC will reengage and normal operation will resume. If the gear ratio becomes intermittent and recovers three times in a given key start, the current gear will be maintained and EMCC inhibited, then the transmission will go into Limp-in mode if throttle is applied below 72 Km/h (45 MPH) or at 35 Km/h (22 MPH) with closed throttle.
- Codes 51, 52, 53, 54, 56, and 57 at speeds between 35 and 72 Km/h (22 and 45 MPH) - If one of these codes is set between 35 and 72 Km/h (22 and 45 MPH), the current gear will be maintained until the gear ratio problem corrects itself. If throttle is applied, the trans will go to 2nd gear. If this happens and the gear ratio problem goes away, normal operation will resume. If three gear ratio problems are identified in a given key start, the current gear will be frozen until throttle is applied. The transmission will then go into Limp-in mode with throttle applied at speeds between 35 and 72 Km/h (22 and 45 MPH)
- Codes 51, 52, 53, 54, 56, and 57 at speeds below 35 Km/h (22 MPH) - If a gear ratio problem is identified below 35 Km/h (22 MPH), the transmission will immediately substitute second gear for the current gear. If the gear ratio problem goes away, normal operation will resume. If three gear ratio problems are identified in a given key start, the transmission will go into Limp-in mode.
In the AutoStick Mode (manual shift mode), upshifts and downshifts are actuated manually. Shift requests are detected by monitoring the upshift and downshift switches. The PCM monitors the above set conditions. A set condition will be tolerated for up to 15 seconds before setting a code.
Transmission Effects: The OD position shift schedule is substituted while operating in the AutoStick gear selector position. No Limp-in mode occurs.
Transmission and engine temperatures are monitored during vehicle operation. If conditions occur causing the engine or transmission to overheat, the AutoStick mode will be canceled, and a code will be set.
Transmission Effects: The 3 position shift schedule that is used in non-AutoStick applications is substituted while operating in the AutoStick gear selector position. No Limp-in mode occurs.
While in 3rd or 4th gear FEMCC and just before the A/C clutch engages, the Engine Control System requests the Transmission Control System to momentarily establish PEMCC operation. If vehicle shudder is detected during the FEMCC to PEMCC transition, a counter is incremented. If the count reaches 20, the trouble code is set. The driver may then notice harsh bumps when the A/C clutch is being cycled, but vehicle shudder will be eliminated. After 35 OBDII (EURO STAGE III OBD) warm-up starts or if the code is cleared, PEMCC will be reactivated to see if shudder is still present. If one shudder event occurs, the code will be reset. Clearing the code and running battery disconnect with the DRBIII® is the only way to reset the shudder counter from 20 back to zero.
Transmission Effects: This code does not cause the transmission to go into Limp-in mode. However, once the code is set, FEMCC to PEMCC operation before the A/C clutch engagement will be disabled for 35 OBDII (EURO STAGE III OBD) warm up starts.
If the transmission oil temperature rises above 115°C (240°F), the overheat shift schedule is activated refer to Transmission Operation as a function of Transmission Oil Temperature and the code is set. The DTC is an information 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 115°C (240°F) 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. 2nd gear partial EMCC above 40 Km/h (25 MPH), 3rd gear EMCC from 45-69 Km/h (28-43 MPH), delayed 3-4 upshift at 69 Km/h (43 MPH), early 4-3 coastdown at 66 Km/h (41 MPH), EMCC operation under all conditions above 40 Km/h (25 MPH) except at closed throttle or 1st gear.
If a vehicle loses power to the PCM, the vehicle will go to the 2nd gear mode since there is no power available to control the transmission solenoids. However if power is restored, the PCM will power-up and normal operation will be restored. This DTC identifies that power to the PCM was restored when the gear selector was in a "Drive" position while the vehicle was moving at speeds above 32 Km/h (20 MPH). If someone shifts to Neutral and cycles the ignition key and quickly shifts to "Drive" while moving before the PCM comes out of its START ROUTINE, the DTC can be set. Therefore it is critical that this DTC diagnosis repair procedure should only be used if the vehicle is experiencing intermittent 2nd gear operation and subsequently a return to normal operation during normal driving.
Transmission Effects: No Limp-in condition. The DTC is for information only when trying to diagnosis intermittent 2nd gear operation and subsequently a return to normal operation.
The Transmission Control System communicates with the MIC using the PCI bus. It relies on certain information to function properly. The Transmission Control System continuously monitors the PCI bus to check for messages broadcast from the Engine Control System.
Transmission effects: Possible improper PCM AutoStick configuration.
The Transmission Control System communicates with the other modules in the vehicle using the PCI bus. It relies on certain information to function properly. The PCM continuously monitors the PCI bus to check for messages broadcast from the certain modules.
Transmission Effects: Possible improper PCM AutoStick configuration and delayed 3-4 shifts. No EMCC and early 3-4 shifts for a few minutes after engine is started.
The Transmission system requires sufficient battery voltage in order to energize the transmission solenoids. The PCM continuously monitors the voltage available to the solenoids.
Transmission effects: At speeds above 72 Km/h (45 MPH) the transmission system will default to neutral. Below 72 Km/h (45 MPH) the transmission system will default to Limp-in mode and the MIL will illuminate after 5 minutes of substituted operation. Manual gear selection of Park, Reverse, Neutral and Second will be available.
The temperature sensor (thermistor) is used to sense the temperature of the transmission fluid. Transmission fluid temperature can affect shift quality, torque converter lockup, and when and if some diagnostics are run. A failed temperature sensor could affect the OBD II diagnostics, therefore when a fault is detected in the temperature sensor circuit, transmission temperature will be based on a calculated temperature value.
Transmission Effects: When the fault is set, calculated temperature is substituted for measured temperature, however the fault code is stored only after three consecutive occurrences of the fault.
The temperature sensor (thermistor) is used to sense the temperature of the transmission fluid. Transmission fluid temperature can affect shift quality, torque converter lockup, and when and if some diagnostics are run. A failed temperature sensor could affect the OBD II diagnostics, therefore when a fault is detected in the temperature sensor circuit, transmission temperature will be based on a calculated temperature value.
Transmission effects: When the fault is set, calculated temperature is substituted for measured temperature, however the fault code is stored only after three consecutive occurrences of the fault.
The temperature sensor (thermistor) is used to sense the temperature of the transmission fluid. Transmission fluid temperature can affect shift quality, torque converter lockup, and when and if some diagnostics are run. A failed temperature sensor could affect the OBD II diagnostics, therefore when a fault is detected in the temperature sensor circuit, transmission temperature will be based on a calculated temperature value.
Transmission effects: When the fault is set, calculated temperature is substituted for measured temperature, however the fault code is stored only after three consecutive occurrences of the fault.
The temperature sensor (thermistor) is used to sense the temperature of the transmission fluid. Transmission fluid temperature can affect shift quality, torque converter lockup, and when and if some diagnostics are run. A failed temperature sensor could affect the OBD II diagnostics, therefore when a fault is detected in the temperature sensor circuit, transmission temperature will be based on a calculated temperature value.
Transmission effects: When the fault is set, calculated temperature is substituted for measured temperature, however the fault code is stored only after three consecutive occurrences of the fault.