Part 2A

NAME OF CODE: P1775(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 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.

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 - LR pressure switch will not close
- LR Pressure Switch Sense circuit shorted to battery

NAME OF CODE: P0740(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/LR solenoid must achieve it's 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 event 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 LR/TCC solenoid until the torque converter slip (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 (no Limpin) 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 Pressure Switch assembly.

NAME OF CODE: P0750(41) - LR Solenoid Circuit
P0755(42) - 2/4 Solenoid Circuit
P0760(43) - OD Solenoid Circuit
P0765(44) - UD Solenoid Circuit

When Monitored: Ignition key is turned from off position to run position and/or ignition key is turned from crank position to run position, then every 10 seconds thereafter, or when a gear ratio or pressure switch error DTC is detected.

Set Condition: All four solenoids are tested for continuity continuously immediately upon start up and during vehicle operation. For solenoids that are currently energized, power is momentarily interrupted, then reenergized. For solenoids that are not currently energized, the solenoid is momentarily energized, then de-energized. Under both situations, if an inductive spike is not sensed by the PCM during the continuity check, it is retested twice. If it fails the test the third time, the appropriate code is set.

Solenoid Application Chart:

Theory of Operation: 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).

Possible Causes:
- Open or shorted solenoid circuit(s) between PCM and Transmission Solenoid/Pressure Switch assembly
- Open ground circuit
- PCM connector problems
- Solenoid/Pressure Switch connector problem
- Solenoid/Pressure Switch assembly
- PCM

NAME OF CODE: P1776(47) - Solenoid Switch Valve Latched in LR Position

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

Set Condition: If the transmission senses the LR 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 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.

Possible Causes:
- Valve body - Solenoid valve stuck in LR position
- Intermittent short to ground or open circuit in
- LR Pressure Switch Sense circuit (with code 24 only)
- Solenoid Pressure Switch (with code P0841(24) only)
- PCM (with code P0841(24) only)

NAME OF CODE: P0736(50) - Gear Ratio Error in Reverse
P0731(51) - Gear Ratio Error in 1st
P0732(52) - Gear Ratio Error in 2nd
P0733(53) - Gear Ratio Error in 3rd
P0734(54) - Gear Ratio Error in 4th
P0715(56) - Input Speed Sensor Error
P0720(57) - Output Speed Sensor Error
P1794(58) - Speed Sensor Ground Error

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 a period of time.
- Codes 50 through 54 sets if the ratio of the input RPM (Nt) to the output RPM (No) does not match the given 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 PCM reset in neutral and Nt/No equals a ratio of input to output of 2.50

A hard code sets within 3 seconds, an intermittent code sets within 15 seconds.

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 54).
2) An excessive change in input or output speeds indicating signal intermittent will result in codes 56 and/or 57 being set.
3) 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.

Possible Causes:
- Code P0736(50) - Excludes geartrain failures which should be obvious upon disassembly.
- If code P0944(35) is also set, follow diagnostic procedure for code P0944(35) first
- Valve body - #1 ball check or LR switch valve sticking - may also set code P0731(51)
- Speed sensor or associated wiring - may also set codes P0731(51), P0715(56), or P0720(57)
- Failed or slipping LR clutch - may also set code P0731(51)
- LR seal leakage (Intermittent no drive or reverse)
- Sticky LR accumulator seals (Intermittent no drive or reverse)
- Failed reverse clutch (hard code)
- OD/Rev lip seal leakage
- Worn reaction shaft support seal rings
- Snap ring out of position

- Code P0731(51) - Excludes geartrain failures which should be obvious upon disassembly
- If code P0944(35) is also set, follow diagnostic procedure for code P0944(35) first
- Valve body - #1 check ball or LR switch valve sticking may also set code P-0736(56) or have no Reverse
- Speed sensor or associated wiring - may also set codes P0736(50), P0715(56), or P0720(57)
- Failed or intermittent slipping UD clutch - may also set P0732(52), or P0733(53)
- UD seal leakage (intermittent)
- Worn input clutch hub bushing (hard code at heavy throttle)
- Sticky UD accumulator seals (intermittent)
- Worn reaction shaft support seal rings (hard code at heavy throttle)
- Solenoid pack (UD pressure in 4th gear
- Failed or slipping LR clutch - may also set code P0736(56) or have no Reverse
- LR seal leakage (Intermittent)
- Sticky LR accumulator seals (Intermittent)

- Code P0732(52) - Excludes geartrain failures which should be obvious upon disassembly
- If code P0944(35) is also set, follow diagnostic procedure for code P0944(35)
- Failed or slipping 2/4 clutch - may also set code P-0734(54)
- 2/4 seat leakage (intermittent)
- Sticky accumulator seals (intermittent)
- Failed or intermittent slipping UD clutch - may also set code P-0731(51) and/or P-0733(53)
- UD seal leakage (intermittent)
- Worn input clutch hub bushing (hard code at heavy throttle)
- Sticky UD accumulator seals (intermittent)
- Worn reaction shaft support seal rings (hard code at heavy throttle)
- Solenoid pack (UD pressure in 4th gear)

- Code P0733(53) - Excludes geartrain failures which should be obvious upon disassembly
- If code P0944(35) is also set, follow diagnostic procedure for code P0944(35) first
- Failed or slipping OD clutch - may also set code P0734(54)
- OD and Reverse inner and outer lip seal leakage (usually hard code)
- Sticky OD accumulator seals (intermittent)
- Worn reaction shaft support seal rings (hard code at heavy throttle)
- Broken OD/UD tapered snap ring - (hard code at heavy throttle)
- Failed or intermittent slipping UD clutch - may also set code P0731(51) and/or P0732(52)
- UD seal leakage (intermittent)
- Worn input clutch hub bushing (hard code at heavy throttle)
- Sticky UD accumulator seals (intermittent)
- Worn reaction shaft support seal rings (hard code at heavy throttle)
- Solenoid pack (UD pressure in 4th gear)

- Code P0734(54) - Excludes geartrain failures which should be obvious upon disassembly
- If code P0944(35) is also set, follow diagnostic procedure for code P0944(35) first
- Failed or slipping OD clutch - may also set code P0733(53)
- OD and Reverse inner and outer lip seal leakage (usually hard code)
- Sticky OD accumulator seals (intermittent)
- Worn reaction shaft support seal rings (hard code at heavy throttle)
- Broken OD/UD tapered snap ring - (hard code at heavy throttle)
- Failed or slipping 2/4 clutch - may also set code P0732(52)
- 2/4 seal leakage (intermittent)
- Sticky accumulator seals (intermittent)

- Codes P0715(56) and P0720(57)
- Failed input or output speed sensor (intermit tent or hard code)
- Shorted or open wiring between PCM and speed sensor(s) (intermittent)
- PCM connector problems and/or Speed Sensor connector

- Code P1794(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 P1799(74)
- PCM