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Name of code:
P-0700(11) - Internal Controller

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

Set Condition: This code is set whenever Transmission Control Module (TCM) senses an internal error.

Theory of Operation: The TCM 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 TCM and/or Trans Control Relay. In fact, this DTC is rarely set due to a TCM error, it is usually set by a poor ground.

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

Possible Causes:
^ TCM ground circuit. (check main ground attachment to engine block)
^ Relay ground circuit. (check main ground attachment to engine block)
^ TCM

Name of code:
P-1792(12) - Battery was Disconnected (Info Only)

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

Set Condition: This code is set whenever Transmission Control Module (TCM) is disconnected from battery power (B+) or ground. It will also be set during the DRBIII(R) Quick 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 reinitialization of some parameters.

Transmission Effects: Loss of trouble code data. The Transmission system will default to the Immediate shutdown routine 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 (Fused B+)
^ TCM disconnected
^ Dead Battery
^ Low battery voltage during cranking
^ Quick Battery Disconnect by DRBIII(R) or MDS
^ Bad TCM ground circuit.

Name of Code:
P-1767(14) - Relay Always On

When Monitored: When 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 Control Relay Output terminal(s) of the TCM 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. The relay output is fed back to the TCM through pins 16, 17, and 36. It is referred to as "Transmission Control Relay Output". This circuit does not supply power to the TCM, it is only a sense circuit. When the relay is off, no power is supplied to the solenoids and pressure switches, and the transmission is in "limp-in" or "default" mode.

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

Possible Causes:
^ Relay contacts stuck together.
^ Short to voltage in Transmission Control Relay output circuit(s).
^ Short to voltage in Transmission Relay Control circuit.
^ Short to voltage on any pressure switch sense circuit.
^ Short to voltage on any solenoid control circuit.
^ TCM connector problems.
^ TCM.

Name of Code:
P-1768(15) - Relay Output Always Off

When Monitored: Continuously

Set Condition: This code is set when less than 3 volts are present at the transmission control relay output (pins 16, 17 and 36) circuits 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 solenoids and pressure switches when the transmission is in normal operating mode. The relay output is fed back to the TCM through pins 16, 17, and 36. It is referred to as "'Transmission Control Relay Output". This circuit does not supply power to the TCM, it is only a sense circuit. When the relay is off, no power is supplied to the solenoids and pressure switches, and the transmission is in "limp-in" or "default" mode.
After a controller reset (ignition key turned to the 94run" 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 will illuminate and the transmission system will default to the Immediate Shutdown routine.

Possible Causes:
^ Transmission Control relay (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
^ Relay connector problem
^ Relay Ground circuit
^ TCM Ground circuit(s)
^ TCM

Name of code:
P-0725(18) - Engine Speed Sensor Circuit

When Monitored: Continuously with engine 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. The TCM uses the RPM data broadcast over the communication bus to determine if the engine is running. The TCM continuously verifies that it's calculated engine speed is within range while the engine is running.

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

Possible Causes:
^ Open or short in engine speed sensor circuit. (Crank sensor signal)
^ TCM connector problems (Crank sensor signal or sensor ground terminals)
^ Open or short in sensor ground circuit
^ TCM
^ PCM.

Name of Code:
P-1716(19) - Bus Communication with Engine Module

When Monitored: Continuously with key on.

Set Condition: If no bus messages are received from the Powertrain Control Module (PCM) for 10 seconds.

Theory of Operation: The TCM communicates with the PCM using the communication bus. It relies on certain information to function properly. The TCM continuously monitors the 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. Generally poor shift quality.

Possible Causes:
^ Open or shorted bus circuit
^ TCM
^ PCM

Name of code:
P-0705(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 TRS T1, TRS T2, TRS T3, TRS T41, and TRS 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 information and determine the shift lever position. Each shift lever position has its own unique combination of closed and open switches. This is called a PRNDL code. There are 5 switches, therefore: there are many possible combinations of open and closed switches (codes). There are 12 valid codes, two for neutral, one for each other gear position (5), and five temporary codes. The remainder of the codes should never occur, these are called invalid codes.

Transmission Effects and possible causes:
^ (This code alone will not illuminate the MIL)
^ TRS connector not plugged in
^ TRS T1, T2, T3, T41, or T42 circuit(s) are either open, shorted to ground, or shorted to 12 volts.
^ TRS
^ TCM
^ Worn Code Plate. Check for heavy wearing by TRS switch contacts
^ Intermittent T1, T2, T3, T41 or T42 circuits. Check for corrosion, terminal push-outs or spread terminals at 60-way TCM connector and/or 23-way transmission connector.
^ These same symptoms may occur without the fault code 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

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 (i.e.: 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). 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 intermittency (excessive signal changes).

Transmission Effects: The MIL will illuminate, the transmission system will not go into limp-in mode. The TCM will use a "calculated throttle angle" supplied by the PCM over the communication bus. If the communication 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. The vehicle may experience extremely erratic transmission shifting just prior to setting the code. If the intermittency does not last long enough to set the code, the customer will say that the transmission violently hunts between gears.

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

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 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 are momentarily 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

Name of code:
P-1790(36) - Fault Immediate After Shift

When Monitored: After a speed ratio error DTC is stored.

Set Condition: This code is set if the associated speed 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 possibly mechanical in nature. When this code exists, diagnosing the transmission should be based on the associated speed ratio code and mechanical causes should be considered first.

Transmission Effects: None

Possible Causes:
^ Mechanical causes as listed under associated speed 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 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. The MIL will illuminate after 5 minutes of substituted gear operation.

Possible Causes:
^ PRNDL indicates a valid OD code in the hydraulic reverse position
^ Valve body - Solenoid Switch Valve stuck in TCC position
^ High idle speed
^ Solenoid malfunction - may also set code P-1784(81)
^ 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) Operation

Set Condition:
a) The transmission must be in EMCC, with the input speed greater than 1750 RPM. The TCC/L-R solenoid must achieve the 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, 2nd Prime, 3rd, or 4th gear, the torque converter clutch (TCC) can be engaged when certain conditions are met. The TCC piston is electronically modulated by increasing the duty cycle of the L-R solenoid until the torque converter slip difference (difference between engine and transmission input speed) is within 60 RPM. Then the L-R 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 (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 38 present.
^ Sticky CC Regulator valve

Name of code:
P-1776(47) - Solenoid Switch Valve (SSV) Latched in L-R Position

When Monitored: Continuously when doing partial or full EMCC (PEMCC or FEMCC)

Set Condition: If the transmission senses the L-R pressure switch closing while performing PEMCC or FEMCC. This code will be set after two unsuccessful attempts to perform PEMCC or FEMCC.

Theory of Operation: The solenoid switch valve (SSV) controls the direction of the transmission fluid when the L-R solenoid is energized. SSV will be in the downshifted position in 1st gear, thus directing the fluid to the L-R 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 L-R pressure switch should indicate no pressure if the SSV is in the TCC position. If the L-R pressure switch indicates pressure while in PEMCC or FEMCC, EMCC operation is aborted and inhibited to avoid inadvertent application of the L-R clutch. Partial EMCC will be attempted if the L-R pressure switch does not indicate pressure. A second detection of L-R pressure results in setting the code.

Transmission Effects: EMCC is inhibited and the transmission system will default to the Orderly Shutdown routine.

Possible Causes:
^ Valve body - Solenoid Switch Valve stuck in L-R position
^ Intermittent short to ground or open circuit in L-R Pressure Switch Sense circuit (with code P-1784 only)
^ Solenoid/TRS assembly (with code P-1784(81) only)
^ TCM (with code P-1784(81) only)

Name of Code:
P-1793(48) - Torque Reduction (TRD) Link Communication Error

When Monitored: During torque managed shifts (Throttle angle above 54 degrees). This system is also tested whenever the vehicle is stopped and the engine speed is below 1000 RPM.

Set Condition: This code is set when the Transmission Control Module (TCM) sends two subsequent torque reduction messages to the Powertrain Control Module (PCM) via the TRD link circuit and does not receive a confirmation from the PCM over the communication bus.

Theory of Operation: During high torque shifts the TCM will send a message requesting that the PCM reduce engine power until the shift is completed. This message is sent from the TCM to the PCM across the Torque Management Request Sense Circuit. The PCM will acknowledge the TCM's request by sending a confirmation message across the communication bus. The TRD Link communication is also tested periodically for operation whenever the engine is running and the vehicle is not moving with zero degrees throttle.

Transmission Effects: Maximum throttle angle used by TCM will be 54 degrees. As a result a customer may complain about loss of performance or of short shifting when driving aggressively.

Possible Causes:
^ Sticky Throttle Position Sensor (TPS)
^ Wiring or Connector problems in the Torque Management Request Sense Circuit
^ Bus communication problems.
^ PCM
^ TCM