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NAME OF CODE: P0613(11, 13, 45, 94) - Internal TCM

When Monitored: Whenever the key is in the Run or Run/Start position.

Set Condition: This code is set whenever Transmission Control System senses an internal error

Theory of Operation: The PCM is constantly monitoring its 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.

Possible Causes:
- PCM ground circuit.
- Relay ground circuit
- PCM

NAME OF CODE: P1684(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 PCM 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 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 reinitialization 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 PCM
- PCM disconnected
- Dead Battery
- Low battery voltage during cranking
- Battery Disconnected by DRBIII or MDS2
- PCM ground circuit missing.

NAME OF CODE: P0891(14) - Transmission Relay 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 PCM senses greater than 3 volts at the Trans Relay Output (switched battery) terminal of the PCM prior to the PCM 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 PCM. It is referred to as the Transmission Control 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.

Possible Causes:
- Relay failure (welded contacts)
- Short to battery in 12-volt supply and/or Transmission Control Relay Output circuit(s)
- Short to voltage
- PCM connector problems
- PCM

NAME OF CODE: P0888(15) - Relay Output Always Off

When Monitored: Continuously

Set Condition: This code is set when less than 3 volts are present at the Transmission Relay Output (switched battery) terminals at the PCM when the PCM 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 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 will illuminates and the transmission system defaults to 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 Trans mission Control Relay circuit(s)
- PCM connector problem
- PCM

NAME OF CODE: P0725(18) - Engine Speed Sensor Circuit

NOTE: This code is not a Transmission Input Speed Sensor DTC

When Monitored: Whenever the engine is running.

Set Condition: This code is set when the engine speed sensed by the PCM is less than 390 RPM or greater than 8000 RPM for more than 2.0 seconds.

Theory of Operation: 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 the 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.

Possible Causes:
- Engine DTC (engine rpm related) present.
- PCM

NAME OF CODE: P1694(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 PCM uses a new dual port RAM internal to the controller to communicate with the Transmission Control System. The Transmission Control System relies on certain engine information to function properly. The Transmission Control System continuously monitors the internal engine 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:
- PCM

NAME OF CODE: P0890(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 PCM senses voltage on any of the pressure switch inputs prior to the PCM 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 PCM. It is referred to as the Transmission Control 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 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.

Possible Causes:
- Short to battery on one or more pressure switch sense circuits
- PCM connector problems
- PCM

NAME OF CODE: P0871(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.

Pressure Switch States:

Theory of Operation: The PCM 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.

Transmission Effects: Normal operation will be experienced if no other codes are present. Transmission Control System will ignore the code. Limp-in condition will only occur if code P0871(21) is present with a code P0706(28).

Possible Causes:
- If code P0944(35) is present, ignore code P0871(21) and perform code P0944 diagnostic procedures
- OD pressure switch sense circuit open or shorted to ground between PCM and solenoid pack
- OD pressure switch sense circuit shorted to battery
- Solenoid Pressure Switch assembly
- Loose valve body bolts
- Plugged filter - internal transmission or torque converter failure
- PCM

NAME OF CODE: P0846(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.

Pressure Switch States:

Theory of Operation: 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.

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.

If the 2/4 pressure switch is open (indicating no 2/4 clutch pressure) in 2nd or 4th gear, the Transmission Control System sets code P0846(22) and continues with normal operation. The transmission will only go into Limpin 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.

Possible Causes:
- If code P0944(35) is present, ignore code P0846(22) and perform code P0944 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 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
- PCM

NAME OF CODE: P0841(24) - LR Pressure Switch Sense Circuit

When Monitored: Whenever the engine is running.

Set Condition: This code is set if the LR pressure switch is either open or closed at the wrong time in a given gear.

Pressure Switch States:

Transmission Range Sensor States:

Theory of 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.

Shift Lever Error Codes Reported By The DRBIII:

This chart lists DRBIII-reported Shift Lever Error codes.

Transmission Effects and Possible Causes:

Scenario 1) - All PRNDL lights stay illuminated indefinitely in Park following a Key start.
- Wrong Part Number PCM for application
- TRS connector not plugged in
- C1 through C4 (T1, T3, T41, or T42) circuits are open, shorted to ground, or shorted to 12 volts.
- PCI bus failure (Open or shorted resulting in no communication to BCM or Cluster)
- TRS
- PCM
- 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 PCM and/or TRS connector
- TRS
- PCM
- BCM

Scenario 3) - If an invalid code happens while operating in the "3" or "L" position, the "3" or "L" shift schedule and electronic display will be frozen (regardless of whether "OD"', "3" or "L" is selected). The display will be frozen until the shifter is moved to the "N" position (all PRNDL lights will illuminate) and then back to the "OD" position. The "N" and "OD" position must be held there for at least 3 seconds in each position 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 PCM and/or TRS connector.
- TRS
- PCM
- BCM

These same symptoms may occur without the code P0706(28) setting. It is possible that the invalid code that was sensed by the PCM 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: P0120(29) - Throttle Position Sensor Signal Circuit

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 (ie: faster than the throttle body motion could occur). The DTC will be set if the engine supplied calculated throttle angle or a fixed 25 degrees of throttle angle is substituted for use by the Transmission control system.

Theory of Operation: The PCM receives the throttle position signal from the Throttle Position Sensor UPS). The PCM uses a new dual port RAM internal to the controller to send the TPS signal to the Transmission Control System. The TPS has a 5-volt pull up supplied from the Powertrain Control Module (PCM). The signal is checked for out-of-range and intermittent operation (excessive signal changes). If the TPS signal is unavailable, the transmission will use a calculated throttle angle supplied by the engine control system. If the Transmission Control System has an internal error which prevents the use of the engine supplied TPS signal, then 25 degrees of throttle angle will be substituted.

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 Transmission Control System will use a calculated throttle angle supplied by the PCM. The PCM will use a default throttle angle of 25 degrees for the key start which code was set. The PCM will try to use the TPS signal again on the next key start. The MIL will illuminate after 5 minutes of substituted operation if the engine controller is not calibrated for throttle substitution.

Possible Causes:
- Open or shorted TPS signal and/or ground circuits
- PCM connector problems
- TPS or TPS connector (Check PCM DTC's)
- PCM

NAME OF CODE:
P0870(31) - OD Hydraulic Pressure Test Failure
P0845(32) - 2/4 Hydraulic Pressure Test Failure
P0992(33) - 2/4/OD 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 PCM 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 PCM 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.

Pressure Switch States:

Possible Causes:
- Pressure switch sense circuit shorted to battery between PCM and solenoid pack.
- Low line pressure
- Solenoid Pressure Switch assembly

NAME OF CODE: P0944(35) - Loss Of Prime

When Monitored: If the transmission is slipping in any forward gear and the pressure switches are not indicating pressure, a loss 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 LR, 2/4 and OD, in 2nd, 3rd, and 4th gear 2/4 and OD) are turned on by the PCM to see if pump prime exists. The code is set if none of the pressure switches respond. The PCM 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 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.

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. Where someone shifts to reverse, reverse is engaged, and then shifts to OD and does not get OD (gets a neutral condition), and then can not get reverse or OD for 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: P1790(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.